Synthesis and Structure of Novel Group 6 Complexes of

Organometallics 1995, 14,4742-4754

4742

Synthesis and Structure of Novel Group 6 Complexes of Dibenzofulvalenes Robert C. Kerber” and Brian Waldbaum Department of Chemistry, SUNY at Stony Brook, Long Island, New York 11794-3400 Received May 15, 1995@ The complexes (u,y5:q5-dibenzo[a,dlfulvalene)M~(CO)~ (la, M = Cr; l b , M = Mo; 4, M = Mo, [af isomer; IC, M = W)were prepared in the cases of Cr and Mo by a one-pot doubledeprotonation, migration, and oxidation sequence starting with (u,q6:q6-3,3’-biindenyl)M2(Co)6 (3a,b)and in the case of W directly from 1,l’-biindenyl and W(CO)3(py)3. The dianion of la reacted with Diazald to give (u,q5:y5-dibenzo[a,dlfulvalene)Cr~(CO)~(NO~2, 15. Crystal structures were determined for 3a, 4, and the trimethyl phosphite substitution product of l b (11). The solid state conformation of 3a apparently results from a compromise between the tendency of the tricarbonylchromium moieties to point in opposite directions and the preference for a n s-trans configuration of the organic ligand. The Mo-Mo bond length in 4 is 3.286(4) compared with 3.371(1) found in (fulva1ene)dimolybdenum hexacarbonyl; both structures exhibit comparable degrees of pyramidalization, although the annulated analogue is significantly more twisted. The Mo-Mo bond of 11 was also shorter (3.317 A) than that of the fulvalene analogue. The degree of twisting found in 11 is intermediate between 4 and (fulva1ene)dimolybdenum hexacarbonyl.

A,

A

Bimetallic compounds have attracted a great deal of attention in recent years on the basis of the idea that the concerted effects of two metals in close proximity should result in novel reactions useful in stoichiometric synthesis and in cata1ysis.l Fulvalene (bicyclopentadienylidene) has provided the foundation for many bimetallic complexes2in part because of the strong bonding of its cyclopentadienyl rings to early and middle transition metals. In contrast to the well-studied cyclopentadienylmetal carbonyl dimers, the fulvalene-bridged analogues are expected to show, and have shown in several cases, enhanced reactivity. This is due, in part, to the ability of the fulvalene ligand to allow for metalmetal bond cleavage while inhibiting fragmentation to mononuclear complexes; the potential for metal-metal cooperativity is maintained thru relative proximity and possibly by communication through the n-bond system of the fulvalene ligand.3 Unique chemistry is also expected as a result of the distortion of the fulvalene ligand seen in several structures of metal-metal bonded bimetallic derivatives. The ring centroids of a planar fulvalene are separated by 4 A,4while most M-M bonds are less than 3.5 A long. Consequently, the fulvalene ligand acquires a pyramidalized structure to accomodate M-M bond lengths of 2.8-3.5 still longer, and

A:

Abstract published in Advance ACS Abstracts, September 15,1995. (1)Review articles include: Muetterties, E. L.; Krause, M. J.Angew. Chem., Int. Ed. Engl. 1983,22, 147-204. Roberts, D. A.;GeoMoy, G. L. Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford, U.K., 1982;Vol. 6, chapter 40, pp 763-877. Gladfelter, W. L.; Geoffroy, G. L. Adu. Organomet. Chem. 1980, 18, 207-73. Beck, W.; Niemer, B.; Wieser, M. Angew. Chem., Int. Ed. Engl. 1993,32,923-49. (2)(a) Tilset, M.; Vollhardt, K. P. C.; Boese, R. Organometallics 1994, 13, 3146-69 and previous papers, cited therein, from the Vollhardt group. (b) El Amouri, H.; Besace, Y.; Vaissermann, J.; Jaouen, G.; McGlinchey, M. J. Organometallics 1994, 13, 4426-30. (c) Delville, M. -H.; Lacoste, M.; Astruc, D. J. Am. Chem. Soc. 1992, 114,8310-1. (3)Desbois, M.-H.; Astruc, D.; Guillin, J.;Maiot, J . P.; Varret, F. J. Am. Chem. SOC.1986,107, 5280. (4)Churchill, M. R.; Wormald, J . Inorg. Chem. 1969,8, 1970. @

possibly more reactive, than those in the analogous cyclopentadienyl dimer^.^ Nonetheless, there are shortcomings to fulvalene as a bridging ligand. Cyclopentadienyl rings almost invariably bond to transition metals in an r5 manner. This results in strong bonding, but the q5-Cp ring occupies three coordination sites of the metal, leaving little room for additional ligands in the case of late transition metals, and it tends to disfavor associative reactions which require reduction in hapticity.6 In contrast, ($indeny1)metalcompounds often display enhanced reactivity in ligand substitution reactions. This phenomenon, termed the “indenyl e f f e ~ t , is ” ~attributed t o the ease of slippage from a nominally 18-electron q5 structure to a 16-electron q3 structure, assisted by restoration of full aromaticity to the benzene ring. The “indenyl effect” may be expected to enhance the reactivity of dibenzofulvalene complexes relative to those of fulvalene. We herein report the synthesis of novel group 6 bimetallic complexes la-c and offer a preliminary comparison of their reactivity with that of the analogous fulvalene compounds. The route to complexes 1 is shown in Scheme 1. Starting material 2,l,l‘-biindenyl,8 is used as a mixture of the d,l and meso forms; it is available in high yield from the CuCl2-mediated oxidative coupling of indenide anionsg and is significantly more stable than dihydrofulvalene, the starting material used in the synthesis of the fulvalene analomes.1° Treatment of 2 with either (5)McGovern, P. A.; Vollhardt, K. P. C. Synlett 1990, 493-500. (6)Cotton, F.A. Disc.Faraday Soc. 1969,47, 79-83. Crabtree, R. H.The Organometallic Chemistry of the Transition Metals; J. Wiley & Sons, Inc.: New York, 1988;pp 104-5. (7)Review: OConnor, J. M.; Casey, C. P. Chem. Reu. 1987,87,30718.More recent examples cited by: Po& A. J. Mechanisms of Inorganic and Organometallic Reactions; Twigg, M. V., Ed.; Plenum Press: New York, 1991;chapter 10,pp 239-41.Szajek, L. P.; Lawson, R. J.;Shapley, J. R. Organometallics 1991, 10, 357-61. Frankcom, J. C.; Green, J . C.; Nagy, A,; Kakkar, A. K.; Marder, T. B. Organometallics 1993,8, 3688-97. Ceccon, A,; Gambaro, A.; Saverio, S.; Valle, G.; Venzo, A. J. Chem. Soc., Chem. Commun. 1989,51-2.Habib, A, Tanke, R. S.; Holt, E. M.; Crabtree, R. H. Organometallics 1989,8, 1225-31.Merola, J. S.; Kacmarcik, R. T. Organometallics 1989, 8, 778-84.

0 1995 American Chemical Society

Group 6 Complexes of Dibenzofulvalenes

Organometallics,'Vol. 14, No. 10, 1995 4743

Scheme 1

Figure 1. ORTEP drawing of 3a showing the labeling scheme. Atoms are represented by thermal ellipsoids at the 30% level. Table 1. Positional Parameters for Compound 3a Cr(C0)3(NH3)311 or Mo(C0)3(py)312(3 equiv) in the presence of EtzO-BF3 in Et20 forms either 3a (43%) or 3b (78%),respectively. In both cases, the double bonds of the organic ligand migrate during complexation to give exclusively the 3,3'-biindenyl complexes. ($-3,3'Biindenyl)Cr(CO)s, 10,as well as reduced compounds 8 and 9, form as side products in the synthesis of 3a, with NH3 conceivably serving as the proton source. Analogous products are not detected in the case of 3b.

Q 9

a

0

3

The ability of the tricarbonylmetal moieties to point either in the same or opposite direction, combined with that of the organic ligand to assume either an s-cis or s-trans conformation, generates four idealized diastereomeric possibilities. Complexes of the type (arene)(Cr(CO)3)2in which the arene is a rigid, fused polycyclic system usually occur as the anti isomer.13 In the case of (p,$?@-biphenyl)(Cr(CO)3)~where the phenyl groups can rotate freely, the benzene rings assume a nearly coplanar conformation, and the tricarbonylchromium moieties are anti.14 Introduction of ortho substituents causes the molecule to twist away from an idealized anti planar arrangement; in cases where an ortho substitu(8) The position of substituents on the five-membered ring of indene are indicated as shown.

(9)Nicolet, P.; Sanchez, J.-Y.; Benaboura, A.; Abadie, M. J. M. Synthesis 1987,202-3. (10) Vollhardt, K. P. C.; Weidman, T. W. Organometallics 1984, 3, 82-6. (11)Peitz, D. J.; Palmer, R. T.; Radonovich, L. J.; Woolsey, N. F.

Organometallics 1993, 12, 4580-4. (12) Nesmeyanov, A. N.; Krivykh,V. V.; Kaganovich, V. S.; Rybinskaya, M. I. J. Organomet. Chem. 1976,102, 185-93. (13)See ref 11. An exception is cis-~,rf:$-9,9-dimethyl-9-silafluorene)(Cr(CO)&: Kirillova, N. I.; Gusev, A. I.; Afanasova, 0. B. Metalloorg. Khim. 1988, 1, 1278. (14) Allegra, G.; Natta, G. Atti. Accad. Naz. Lincei 1961, 31, 399.

atom

X

0.71 179(9) 0.5697(5) 0.5944(4) 0.8853(4) 0.6435(6) 0.6358(6) 0.7322(7) 0.8354(7) 0.8426(9) 0.7482(8) 0.733(1) 0.610(1) 0.5595(6) 0.6245(6) 0.6400(6) 0.8162(6) 0.5636 0.7265 0.9021 0.9165 0.7803 0.7506 0.5707

Y

z

0.12815(8) -0.0224(3) 0.2050(4) 0.0578(4) 0.2289(5) 0.1548(5) 0.1059(5) 0.1320(8) 0.2056(9) 0.2543(7) 0.3370(7) 0.3545(5) 0.2930(5) 0.0350(5) 0.1736(5) 0.0837(5) 0.1347 0.0524 0.0942 0.2214 0.3800 0.3370 0.4058

0.2110(1) 0.1347(6) --0.0457(5) 0.1014(6) 0.3082(6) 0.3706(7) 0.4192(7) 0.4063(8) 0.344(1) 0.2949(8) 0.230(1) 0.2085(8) 0.2525(7) 0.1648(8) 0.0521(8) 0.1420(7) 0.3812 0.4630 0.4422 0.3357 0.2822 0.1471 0.1677

ent is present on both rings, the arene tricarbonylchromium moieties are nearly perpendicular.15 Only one diastereomer of 3a could be detected (NMR, IR) even in initial reaction mixtures. The crystal structure (Figure 1 and Tables 1and 2) showed this t o be the (d,Z) isomer (i.e., M(C0)3 groups cis as shown in Scheme 1). Conformationally, the organic ligand is twisted away from an idealized (anti, s-cis) conformation, the torsion angle defined by C(8)-C(9)-C(9)'-C(S)' being -51(2)". MM316 force field calculations on the free ligand (3,3'biindenyl) favor a nearly s-trans minimum, the torsion angle mentioned above being -145". The solid state conformation of 3a apparently results from a compromise between the tendency of the tricarbonylchromium moieties to point in opposite directions and the preference for an s-trans configuration of the organic ligand. The two halves of the molecule are related by a crystallographic CZaxis through C(9)-C(9)'. Note that the Cr(CO)3 moieties assume a staggered conformation with respect to the benzene rings. (15) Rose-Munch, F.; Bellot, 0.;Mignon, L.; Semra, A.; Robert, F.; Jeannin, Y. J. Organomet. Chem. 1991, 402, 1-16. Halwax, E.; Vollenkle, H. Monatsh. Chem. 1983, 114, 687. (16) Force field calculations were performed on a Silicon Graphics Indy workstation running MacroModel 3D version 4.0 implementing Allinger's MM3 force field (Allinger, N. C. J.Am. Chem. SOC.1989, 111, 8552) with a parameter set from the 1991 version.

Kerber and Waldbaum

4744 Organometallics, Vol. 14,No. 10, 1995

Table 2. Selected Bond Distances and Angles in 3a Intramolecular Distancesa 2.236(7) Cr(l)-C(ll) 2.233(7) Cr(l)-C(12) 2.203(7) O(l)-C(lO) 2.199(8) 0(2)-C(ll) 2.205(9) 0(3)-C(12) 2.22(1) C(9)-C’(9) 1.838(8)

Cr(l)-C(l) Cr(l)-C(2) Cr(l)-C(3) Cr(l)-C(4) Cr(l)-C(5) Cr( 1)-C(6) Cr(l)-C(10)

Intramolecular Bond Anglesa C(l)-Cr(l)-C(lO) 116.6(3) C(5)-Cr(l)-C(lO) 89.7(3) C(5)-Cr(l)-C(ll) C(l)-Cr(l)-C(ll) C(l)-Cr(l)-C(l2) 153.2(3) C(5)-Cr(l)-C(l2) C(2)-Cr(l)-C(lO) 90.8(3) C(6)-Cr(l)-C(lO) 116.0(3) C(6)-Cr(l)-C(ll) C(2)-Cr(l)-C(ll) C(2)-Cr(l)-C(l2) 154.7(3) C(6)-Cr(l)-C(l2) 91.1(3) C(lO)-Cr(l)-C(ll) C(3)-Cr(l)-C(lO) 152.8(3) C(lO)-Cr(l)-C(l2) C(3)-Cr(l)-C(ll) 117.9(3) C(ll)-Cr(l)-C(l2) C(3)-Cr(l)-C(l2) C(4)--Cr(l)-C(lO) 118.0(5) Cr(l)-C(lO)-O(l) 152.4(5) Cr(l)-C(ll)-O(2) C(4)-Cr(l)-C(ll) C(4)-Cr(l)-C(l2) 91.1(3) Cr(l)-C(12)-0(3)

1.827(8) 1.824(8) 1.142(7) 1.153(7) 1.154(7) 1.47(1)

154.6(5) 115.8(4) 90.5(4) 153.6(3) 89.5(4) 116.3(3) 89.7(3) 90.1(3) 89.3(3) 179.2(7) 177.3(7) 177.3(7)

better fit the [a,dlisomer, and the mechanism given for its formation by base-induced decomposition of dibromotruxane did not preclude the formation of the [a,dl isomer. In a subsequent paper,21Anastassiou referred to the product without comment as the [a,dl isomer. The [afl isomer was next mentionedzz in 1987 as having been formed along with the [a,dl isomer by deprotonation and oxidation of a dihydro precursor, but no data were given. In our hands, at least 10 trials following the literature p r e p a r a t i ~ nof~dibenzo[a,dlfulvalene-double ~ deprotonation of 2 in THF followed by oxidation at -78 “C with either CuCl2 or AgBF4-failed to produce anything except low yields of 1,3’- or 3,3’-biindenyl and substantial red tarry material that would not elute from a column. In contrast, reaction of 1equiv of bromine with the doubly-deprotonated hydrocarbon results in formation of 5 and 6 (ca. 1.7:l). The structure of 5 was Br

Torsion or Conformation Anglesb (U(2)(3)(4)

angle

(1)(2)(3)(4)

angle

C(l)C(9)C’(9)C’(l) C(l)C(9)C’(9)C(8)

-55(1) 126.9(5)

C(4)C(5)C(6)C(7) C(8)C(9)C’(9)C’(8)

176.5(8) -51(2)

=Distances are in angstroms, and angles are in degrees. Estimated standard deviations in the least significant figure are given in parentheses. The sign is positive if when looking from atom 2 to atom 3 a clockwise motion of atom 1would superimpose it on atom 4.

NMR spectroscopy on 3b was not feasible as it is highly insoluble (as is 3a) in most common solvents and, to the extent that it does dissolve, decomposes very quickly to give 3,3’-biindenyl. This greater lability of (arene)Mo(CO)aversus (arene)Cr(CO)s is highly precedented.17 Double deprotonation of either 3a or 3b results in migration’* of both tricarbonylmetal moieties to the fivemembered rings (based on IR and ‘H NMR) to give the bis-q5-dianions3 a and 3%. The ‘H NMR for 3%shows two diastereomers, presumably arising from two diastereomers present in samples of 3b. Subsequent lowtemperature treatment with ferrocenium fluoroborate converts 3% to both l b (54%) and 4 (ca. 5%). This provides additional evidence that 3b occurs as a mixture of diastereomers, in contrast to 3a which gives exclusively l a (ca. 49%). Compound 4 is of particular interest when viewed as a transition metal complex of the enigmatic dibenzo[a,flf~lvalene.~~ Dibenzo[a,flfulvalene was first claimed by Anastassiou20in 1966, but the accompanying spectroscopic data (17) Davis, R.; Kane-Maguire, L. A. P. Molybdenum Compounds

with $-.la Carbons Ligands. In Comprehensive Organometallic Chem-

istry; ed. Wilkinson, G.,, Stone, F. G. A., Abel, E. A,, Eds.; Pergamon: Oxford, U.K., 1982; Vol. 3, pp 1212, 1215. (18)(a) Novikova, L. N.; Ustynyuk, N. A.; Zvorykin, V. E.; Dneprovskaya, L. S.; Ustynyuk, Yu. A. J . Organomet. Chem. 1985, 292, 237-43. (b) Nesmeyanov, A. N.; Ustynyuk, N. A.; Novikova, L. N.; Rybina, T. N.; Ustynyuk, Yu. A.; Oprunenko, Yu. F.; Trifonova, 0. I. J. Organomet. Chem. 1980,184, 63-75. (c) Nesmeyanov, A. N.; Ustynyuk, N. A.; Makarova, L. G.; Andre, S.; Ustynyuk, Yu. A,; Novikova, L. N.; Luzikov, Yu. N. J . Organomet. Chem. 1978,154,4563. (d) Nicholas, K. M.; Kerber, R. C.; Stiefel, E. I. Inorg. Chem. 1971, 10,1519. (19) The bonds in the parent fulvalene are labelled as shown. Dibenzofulvalenes are named according to which bonds are benzannulated.

Bi

Bf

5

6

determined by ‘H and 13C NMR and MS, and confirmed by a low-quality crystal structure (two carbons were non-positive-definite)which showed it to be the S,S,S,Sisomer, as pictured (we assume the molecule occurs as a racemic mixture along with the R,RP,R-isomer). The structure of 6 was inferred from its ‘H NMR spectrum, as it was never obtained totally pure. The stereochemistry of 6 has not been definitively determined, but we infer that the bromines are trans from the lack of coupling of the associated protons and by comparison to 5. Additional runs employing either 1 or 2 equiv of bromine yielded inconsistent results, forming 5 and 6 in variable yields and ratios. Use of 3 equiv or more, with quick addition of the bromine, consistently produces fairly pure 5 (ca. 67%) by trapping the dibenzo[a,dlfulvalene as it forms and so protecting it from polymerization. Treatment of 5 with NaI in acetone at room temperature consistently gives the [a,dl isomer after column chromatography but in variable yields (22 to 68%). We have found that the [a,dl isomer can be synthesized directly from doubly-deprotonated 2 at -78 “C by employing 1equiv of dibromine as oxidizing agent ifdiethyl ether is substituted for THF as solvent. Again, variable yields (36-51%) result. Care must be taken during workup of the crude product as dibenzo[a,dlfulvalene has shown itself t o be exquisitely acid sensitive, a fact hitherto unmentioned in the literature (see Experimental Section). It turns out that a small amount of the [a,fl isomer (~4%) is formed in the above mentioned syntheses. In addition, we have found that both [a,fl and [a,dIisomers form, in varying ratios, as side products from various (20) Anastassiou, A. G.; Setliff, F. L.; Griffin, G. W. J. Org. Chem. 1966,31,2705-8. (21) Anastassiou, A. G.; Griffin, G. W. J. Org. Chem. 1968,33, 3441-8. (22) Escher, A,; Rutsch, W.; Neuenschwander, M. Helu. Chim. Acta 1987,70, 1623-37. (23) Escher, A.; Rutsch, W.; Neuenschwander, M. Helu. Chim. Acta 1988,69, 1644-54.

Group 6 Complexes of Dibenzofulvalenes

Organometallics, Vol. 14, No. 10, 1995 4745

Table 3. Positional Parameters for ComDound 4 ~~

atom

X

0.0960( 1) 0.1848(1) 0.0936(9) 0.275(1) 0.3014(8) 0.333( 1) 0.2602(9) 0.089(1) 0.048(1) 0.021(1) -0.033(1) -0.036(1) 0.011(1) 0.021(2) 0.072(2) 0.116(1) 0.107(1) 0.052(1) 0.051(1) 0.097( 1) 0.122(1) 0.094(1) 0.107(1) 0.145(1) 0.177(2) 0.164(2) O.lOO(1) 0.214(1) 0.258(1) 0.278(1) 0.229(1) 0.091(2) -0.0624 -0.0655 -0.0015 0.0804 0.1529 0.1407 0.0226 0.1081 0.0882 0.1504 0.2088 0.1852

Y

0.7833(1) 0.6359(1) 0.700(1) 0.8426(9) 0.7399(8) 0.535(1) 0.6522(8) 0.908(1) 0.785(1) 0.719(2) 0.741(1) 0.817(1) 0.848( 1) 0.916(1) 0.930( 1) 0.873(1) 0.804(1) 0.651(1) 0.598(1) 0.539(1) 0.546( 1) 0.6155(9) 0.637(1) 0.589( 1) 0.525(2) 0.501(1) 0.731(1) 0.816(1) 0.704( 1) 0.570(1) 0.652(1) 0.862(2) 0.7077 0.8432 0.9576 0.9789 0.8825 0.7658 0.6030 0.4978 0.6856 0.6012 0.4955 0.4537

Table 4. Selected Bond Distances and Andes in 4 ~

Intramolecuilar Distancesa 3.286(4) Mo(2)-C( 13) 2.37(2) M0(2)-C(14) 2.38(2) M0(2)-C(21) 2.33(2) M0(2)-C(22) 2.30(2) M0(2)-C(23) 2.41(2) M0(2)-Cp2 1.95(3) 0(1)-C(19) 2.030) 0(2)-C(20) 1.95(3) 0(3)-C(21) 2.013(2) 0(4)-C(22) 2.3 1(1) 0(5)-C(23) 2.33(2) 0(6)-C(24) 2.31(2)

2

0.1592(1) 0.1721(1) 0.352(1) 0.330(1) 0.179( 1) 0.315(2) 0.455(1) 0.296(2) -0.052(1) -0.037(1) -0.012(2) -0.009(2) -0.040(2) -0.057(2) -0.085(2) -0.090(2) -0.070(2) -0.013(1) 0.062(2) 0.077(2) 0.004(2) -0.055(1) -0.142(2) -0.164(2) -0.100(2) -0.020(2) 0.287(2) 0.270(2) 0.184(1) 0.261(2) 0.349(2) 0.246(2) 0.0013 0.0108 -0.0469 -0.1073 -0.1075 -0.0667 0.0967 0.1316 -0.1840 -0.2272 -0.1155 0.0193

Mo( l)-Mo(2) Mo( 1)-C( 1) Mo(l)-C(2) Mo(l)-C(3) Mo( 1)-C(4) Mo(l)-C(5) Mo( 1)-C( 19) Mo(l)-C(20) Mo(1)-C(24) Mo(l)-Cpl M0(2)-C(10) M0(2)-C( 11) M0(2)-C(12)

2.44(2) 2.41(2) 1.95(2) 1.96(2) 1.97(2) 2.020(2) 1.15(4) 1.12(3) 1.18(3) 1.11(3) 1.14(3) 1.12(4)

Intramolecular Bond Anglesa C(19)-Mo(l)-C(20) 99.4(9) Mo(l)-C(20)-0(2) C(19)-Mo(l)-C(24) 80(1) M0(2)-C(21)-0(3) C(20)-Mo(l)-C(24) 81(1) M0(2)-C(22)-0(4) 85(1) M0(2)-C(23)-0(5) C(21)-M0(2)-C(22) C(21)-M0(2)-C(23) 94.5(9) Mo(l)-C(24)-0(6) 81(1) C(2)-C(lO)-Cp2 C(22)-M0(2)-C(23) Mo(l)-C(l9)-0(1) 172(2) C(lO)-C(B)-Cpl

171(2) 171(2) 177(2) 171(2) 179(3) 176(1) 166(2)

Torsion or Conformation Anglesb (1)(2)(3)(4)

angle

Mo(l)Mo(2)C(lO)C(2) 17(2) M0(2)Mo(l)C(2)C(l0) 16(2) C(3)C(2)C(lO)C(ll) -14(2) C(3)C(2)C(lO)C(14) 167(1) C(l)C(2)C(lO)C(14) -33(3) C( 1)C(2)C(lO)C(11) 146(2) a

(1)(2)(3)(4)

angle

C(19)Mo(l)M0(2)C(21) -132.6(7) C(l9)Mo(l)Mo(Z)C(23) -35.8(9) C(20)Mo(l)M0(2)C(21) -31.1(9) C(20)Mo(l)Mo(Z)C(23) 66(1) CplMo(l)M0(2)Cp2 -25.9(1)

See footnote a of Table 2. See footnote b of Table 2.

H3

4.3

thermal and photochemical reactions of lb (which is uncontaminated by 4). In CDCl3 at 250 MHz the [a,fl isomer exhibits the following: 6 6.90 (d, 5.9 Hz, 2H), 6 6.94 (d, 5.5 Hz, 2H), 6 7.25 (m, 6H), 6 8.36 (d, 6.8 Hz, 2H). Corroborating this assignment, an lH N M R sample initially containing an equimolar mixture of the [a,fl and [a,dl isomers (based on integral ratios) which was stored for 2 days in the dark at 0 "C as a semisolid (it tenaciously retained solvent) later showed a 2.3:l enrichment of the more stable [a,dl isomer; allowing the sample to sit in solution a t room temperature in the dark an additional 16 h increased the preponderance of the [a,dl form to 3:l. This ratio did not change further after the sample was allowed to sit in solution a t room temperature in the light for several more days. MM316 calculations place the [a,fl isomer at 12.79 kJ1 mol higher energy than the [a,dl form. That 4 is a complex of dibenzo[a,flfulvalene was proven by an X-ray structure (Tables 3 and 4); an

ORTEP diagram is presented in Figure 2. The MoMo bond length is 3.286(4) A compared to 3.371(1) A found in (fulvalene)dimolybdenumhexacarbonyl, FvM02( C O ) S . ~Both ~ five-membered rings are nearly planar with a dihedral angle 8 between them of 28.2", compared t o 15.3" found in FvMoz(C0)s. The difference is due to greater twisting in 4. As a measure of pyramidalization, Vollhardt's dihedral angle24 8, defined as the angle between the planes defined by the five-membered rings, proves descriptive only for untwisted structures; large twist angles result in anomalously large values of the dihedral angle 8. We have found the average of the angles C(4)-C(5)-Cp(2) and C(5)-C(4)-Cp(l) (where

(24)Drage, J. S.;Vollhardt, P. C. Organometallics 1986,5, 280297. (25)Abrahamson, H.B.; Heeg, M. J.Inorg. Chem. 1984,23,22816. (26)Kretchmar, S.A.;Cass, M. E.; Turowski, P. N. Acta Crystallogr. 1987,C43,435-7. (27) Begley, M.J.; Puntambekar, S. G . ; Wright, A. H. J. Chem. SOC.,Chem. Commun. 1987,1251-2. (28)Kerber, R. C.; Miran, M. J.; Waldbaum, B.; Rheingold, A. L. Organometallics 1995,14,2002-8.

(29)Seyferth, D.; Anderson, L. L.; Davis, W. B.; Cowie, M. Organometallics 1992,11, 3736-44. (30) Girard, L.; Decken, A.; Blecking, A.; McGlinchey, M. J. J . Am. Chem. SOC.1994,116,6427-8. (31)Kahn, A. P.; Boese, R.; Bliimel, J.; Vollhardt, K. P. C. J . Organomet. Chem. 1994,472,149-162. (32)Weidman, T.W.; Vollhardt, K. P. C. J. A m . Chem. SOC.1983, 105,1676-7. (33) Song, J.3.;Han, S.-H.; Nguyen, S. T.; Geoffroy, G. L.; Rheingold, A. L. Organometallics 1990,9,2386-95.

02

Figure 2. ORTEP drawing of 4 showing the labeling scheme. Atoms are represented by thermal ellipsoids at the 30% level.

Kerber and Waldbaum

4746 Organometallics, Vol. 14, No. 10, 1995

C(1) and C(ll)-C(lO)-C(2)-C(3). MM316 calculations on uncomplexed dibenzo[a,flfulvalene find an energy 3.2 minimum at 18". The analogous twist angle in Fv3.1 M02(CO)6 is 4.3". $ 3 Compounds la,b and 4 are also accessible by direct $ 2.9 reaction of doubly deprotonated 2 with M(CO)6 (M = gm 2.8 Cr, Mo) in refluxing B u ~ O followed ~ ~ by addition of 2.7 ferrocenium fluoroborate at -78 "C. 2.6 Compound IC forms directly in 14% yield from 2, 2.5 2.4 W(CO)3(py)3,and Et20.BF3 at 70 "C, no his@ interme7 8 9 10 I 1 12 13 14 15 diate being detected. The reaction of indene under Bend Angle w similar conditions gives (175-C9H7)WH.18aIt is plausible a. 11,this work. that IC is formed via an analogous dihydride which b. FvMo~(C0)6, ref.24. subsequently loses H2 during heating. C. FVW2(C0)6,ref. 25. Compounds la-c are exceptionally insoluble in comd. FvMo2(C0)4(PMe3)2,ref. 26. e. 4,this work. mon solvents; attempts to recrystallize l b resulted in f. (l-0xacyclopent-2-ylidene)FvMo~(C0)~, ref. 24. microcrystals not suitable for X-ray diffraction. To the g. (~,p3:113.anthracene)Fe2(co)6,ref 27. extent that it does dissolve, l a quickly decomposes to h. (~l,rl~:rl3-biallylene)Fe2(CO)5PPh3, ref. 28. dibenzo[a,d]fulvalene as evidenced by 'H and 13CNMR i. cis-(~,~3:~3-2,2-bi(3-phenylthioallyl))Fe2(CO)~, ref. 29. j. (1,2,4,5-tetramethylenebenzene)Fe3(CO)~, ref. 30. spectroscopy. Compound l b is indefinitely stable in k. Fv(0C) WRh(CO)C(O)Me, ref. 31. solution (under N2) except in DMSO in which it slowly I. ~~,~5:~~-dibcnzo~a,d~ful~alene)Mo~(CO)~~~~C~C~~), unpublished results. decomposes to dibenzo[a,dlfulvalene. No signs of dem. (~l.r13:r13-biallylene)Fe2(C0)6, ref.28. composition of IC in DMSO were witnessed. The n. FvRu (CO)4, ref.32. 0. (Cl2,Y5 :~3-2,2'-biallyl)-(~3-phenylimido)Fe3(CO)~, ref.33. increased lability of l a may be due, in part, to the relative weakness of the Cr-Cr bond as compared with Figure 3. Correlation of bend angle o with metal-metal Mo and W.35 In addition, Nesmeyanov and co-workers bond length. found that the stabilities of $-indeny1 and -fluorenyl complexes increase on going from Cr to Mo to W.18cA the Cp's are the five-membered ring centroids), the bend more stable bis-y5 derivative, 15, was synthesized by angle o, to be a better measure of intrinsic pyratreating 3 a with Diazald at -78 "C in Et20 to give (475: midalization: A plot (Figure 3) of metal-metal bond ~5-dibenzo[a,dlfulvalene)[Cr(CO~2NOl~ in 16% yield. lengths versus bend angle w for a series of 15 bimetallic Photolysis of l b in THF at 300 nm in the presence of fulvalene and biallylene compounds gives a linear excess P(OCH& for 3 days gives the monosubstitution correlation coefficient of -0.893. When the dihedral product, 11, in 29% yield. In contrast, FvMo2(CO)s was angle is used instead, the correlation drops to -0.498. reported to be inert to PPh3 and P(OCH3)3under similar The bend angles for 4 and FvMoz(C0)s are 9 and 7.3", photolytic condition^.^^ An ORTEP diagram for 11 respectively, indicating comparable degrees of pyrami(Tables 5 and 6) is presented in Figure 4. The P(OCH3)3 dalization. In 4, the two five-membered rings are ligand occupies a pseudo-axial position in the "sawhorse" twisted about the C(4)-C(5) bond by approximately 24", structure. The Mo-Mo bond length is 3.3172(8)A, still the average of the torsion angles C(l4)-C(lO)-C(2)3.4

3.3

I

Table 5. Positional Parameters for Compound 11 X

0.63526(2) 0.55543(2) 0.69955(5) 0.6249(2) 0.5419(2) 0.5323(2) 0.5064(2) 0.4384(2) 0.5820(2) 0.5895(2) 0.4956(2) 0.7020(2) 0.4777(2) 0.6574(2) 0.4554(2) 0.7134(2) 0.6094(2) 0.4943(2) 0.5701(2) 0.4269(2) 0.6381(2) 0.6356(2) 0.6817(3) 0.7113(1) 0.7482(1) 0.5926(2) 0.6383(2) 0.6085(2) 0.5749(2)

Y 0.42576(3) 0.54844(4) 0.3255(1) 0.5476(4) 0.5288(4) 0.6229(4) 0.4739(4) 0.5029(5) 0.4959(4) 0.4048(4) 0.6267(4) 0.5152(5) 0.5361(4) 0.4846(4) 0.3499(5) 0.6048(6) 0.6271(5) 0.3781(4) 0.4523(5) 0.4125(6) 0.6404(4) 0.3964(4) 0.6666(5) 0.2838(3) 0.3584(3) 0.2606(3) 0.6801(3) 0.3248(4) 0.3993(4)

2

X

0.65646(4) 0.78684(4) 0.6528(2) 0.5206(5) 0.5982(5) 0.6254(5) 0.6520(5) 0.7705(6) 0.5386(5) 0.4990(5) 0.7002(6) 0.4457(6) 0.7133(5) 0.4751(5) 0.7051(6) 0.4631(6) 0.8077(5) 0.6523(6) 0.8980(6) 0.7636(6) 0.5370(6) 0.4660(5) 0.5087(6) 0.7713(4) 0.6031(4) 0.7798(5) 0.8189(5) 0.7366(5) 0.9668(5)

0.5276(2) 0.7478(3) 0.5372(2) 0.7715(2) 0.6915(2) 0.6990(1) 0.6696(2) 0.6615(3) 0.4197 0.7245 0.4475 0.7443 0.5141 0.3992 0.6167 0.6904 0.7517 0.7424 0.7770 0.7773 0.7998 0.7525 0.6328 0.6660 0.6568 0.5486 0.5667 0.4842 0.6503

Y 0.6576(4) 0.2168(5) 0.6152(5) 0.4363(6) 0.5029(4) 0.2381(3) 0.4767(4) 0.1749(6) 0.5460 0.4735 0.2856 0.6275 0.3341 0.3904 0.6853 0.7300 0.1978 0.1631 0.2428 0.4280 0.4465 0.4903 0.2044 0.1253 0.1461 0.6764 0.3570 0.6813 0.3387

2

0.9979(4) 0.7846(7) 0.9214(6) 0.6476(7) 0.8576(4) 0.5718(4) 0.7850(6) 0.5689(8) 0.8120 0.4141 0.6999 0.4435 0.6160 0.7993 0.5665 0.5204 0.8586 0.7390 0.7590 0.7258 0.6111 0.6400 0.5508 0.5175 0.6418 0.5986 0.4971 0.7367 0.4415

Group 6 Complexes of Dibenzofulvalenes

Organometallics, Vol. 14, No. 10,1995 4747

Scheme 2

i$2eq.lW'F4;-78C

' 2

Table 6. Selected Bond Distances and Andes in 11

HI3

€B

~~

Intramolecular Distances* 3.3172(8) M0(2)-C(20) 2.367(2) M0(2)-C(19) 2.428(6) M0(2)-C(21) 2.332(6) M0(2)-Cp2 2.337(6) P(1)-0(5) 2.433(6) P(1)-0(4) 2.335(6) P(1)-0(8) 1.919(6) C(20)-0(2) 1.984(7) C(19)-0(1) 2.039(6) 0(5)-C(23) 2.325(6) 0(4)-C(22) 2.324(6) 0(6)-C(24) 2.417(6) 0(3)-C(21) 2.322(6) 0(7)-C(25) 2.430(6) 0(8)-C(26)

Mo(l)-M0(2) Mo( 1)-P( 1) Mo(l)-C(14) Mo(l)-C(4) Mo(l)-C(3) Mo( 1)-C( 1) Mo( 1)-C( 2) Mo(l)-C(24) Mo(l)-C(25) Mo(l)-Cpl Mo(2)-C(5) M0(2)-C(13) Mo(2)-C(6) M0(2)-C(12) M0(2)-C(11)

Intramolecular Bond Angles" P(l)-Mo(l)-C(24) 81.9(2) 0(4)-P(1)-0(8) P(l)-Mo(l)-C(25) 81.2(2) C(4)-C(5)-Cp2 C(24)-Mo(l)-C(25) 95.4(3) C(5)-C(4)-Cpl C(20)-M0(2)-C(19) 98.7(3) M0(2)-C(20)-0(2) C(20)-M0(2)-C(21) 79.7(3) M0(2)-C(19)-0(1) C(19)-M0(2)-C(21) 81.1(3) P(1)-0(5)-C(23) Mo(l)-P(1)-0(5) 112.7(2) P(1)-0(4)-C(22) Mo(l)-P(1)-0(4) 121.1(2) Mo(l)-C(24)-0(6) Mo(l)-P(1)-0(8) 119.4(2) M0(2)-C(21)-0(3) 0(5)-P( 1)-O(4) 105.1(2) P(1)-0(8)-C(26) 0(5)-P(1)-0(8) 104.5(2) Mo(l)-C(25)-0(7)

1.953(6) 1.981(7) 1.962(7) 2.029( 7) 1.587(5) 1.607(5) 1.600(5) 1.147(8) 1.14(1) 1.448(9) 1.42(1) 1.160(8) 1.14(1) 1.146(8) 1.42(1) 90.9(2) 173.5(6) 172.8(6) 173.7(6) 173.7(6) 120.8(5) 120.9(4) 176.1(6) 176.8(7) 122.1(5) 176.0(5)

Torsion or Conformation Anglesb (1)(2)(3)(4)

angle

Mo(l)Mo(Z)C(5)C(4) M0(2)Mo(l)C(4)C(5) C(14)C(4)C(5)C(13) C(14)C(4)C(5)C(6) C(13)C(5)C(4)C(3) C(6)C(5)C(4)C(3)

-14.6(3) -14.4(3) 16.7(9) -156.3(6) -171.7(6) 15.3(9)

a

(1)(2)(3)(4)

angle

C(ZO)Mo(Z)Mo(l)C(24) 134.5(3) C(20)M0(2)Mo(l)C(25) 37.5(3) C(lQ)M0(2)Mo(l)C(24) 33.1(3) C(19)M0(2)Mo(l)C(25) -63.9(3) Cp2M0(2)Mo(l)Cpl 24.2(3)

See footnote a of Table 2. See footnote b of Table 2.

shorter than that found in FvMoz(C0)a even though substitution of a phosphine ligand for a carbonyl tends to increase metal-metal bond lengths. The dihedral angle 8 between the two five-membered rings is 21.1", while the bend angle w is 7". The two rings are twisted relative to each other about the C(4)-C(5) bond by 16" (the average of the torsional angles C(3)-C(4)-C(5)C(6) and C(14)-C(4)-C(5)-C(13)). The indenyl ring bound to Mo(2) exhibits an angle of 5.0" between the five- and six-membered rings and an angle of 9.2" between the plane defined by C(5)-C(13)-C(12) and the six-membered ring; the other indenyl unit is more nearly planar with corresponding angles of 2.1 and 5.7". Both metals are distorted toward an r3bonding mode; this tends t o slightly decrease the metal-metal bond length compared to the fulvalene analogue. If 2,2'-biindenyl, 7,36is substituted for 2 as in Scheme 2, then the first step can be carried out successfully to

12

HE

HI

Figure 4. ORTEP drawing of 11 showing the labeling scheme. Atoms are represented by thermal ellipsoids at the 30% level. give the analogous (arene)&(CO)e (M = Cr, Mo) complexes, 13a (85%)and 13b (88%), both high-melting, highly insoluble compounds. In the case of 13a, in contrast t o 3a, both diastereomers form in approximately equal amounts, as evidenced by 'H NMR spectroscopy in DMSO-ds. A similar analysis of 13b proved infeasible due to its extreme lability in DMSO. Both 13a and 13b can be doubly deprotonated with corresponding migration of the M(CO)3 units to the fivemembered rings giving 13a and 13%,as evidenced by lH NMR spectroscopy; however, attempts to convert the dianions to the corresponding neutral metal-metal bonded species (analogues of la,b) by treatment with various oxidizing agents failed. In particular, treatment of 13'a with either CuClz or Br2 in THF at -78 "C resulted in recovery of 7. Treatment of 13'a with either l,2-dibromoethane or 12 in Et20 a t -78 "C resulted in 7 and the monochromium compound (q6-7)Cr(C0)3,14. With 12, (d,l)-l,l'-bi(2,2'-biindenylyl),3716, formed as well. Note that 16 formally results from oxidative coupling of monodeprotonated 7. Treatment of 13% with ferrocenium tetrafluoroborate as in Scheme 2 resulted in 12 in 9% yield. Treatment of 13'a under similar conditions gave a crude product which proved

4748 Organometallics, Vol.14,No.10, 1995

Kerber and Waldbaum

Trifluoroacetic acid was distilled immediately before use. too labile to purify but whose IR and IH NMR spectra Diethyl ether and tetrahydrofuran were distilled over Na closely resemble those of 12. The lH NMR of this under dinitrogen immediately before use. Dibutyl ether was product, presumably the analogous chromium dimer, distilled in uacuo and stored under dinitrogen. l-Methyl-2was significantly broadened, possibly due to partial pyrrolidinone was anhydrous, 99+% grade purchased from homolytic cleavage of the relatively weak Cr-Cr bond. Aldrich in a Sure/Seal bottle. Acetone was HPLC grade and In benzonitrile solution, [CpCr(C0)33~ is in rapid equiwas sparged with dinitrogen for 10 min before use. CuCl2 was librium with its monomeric subunits, the latter existing dried at 110 "C for 24 h before use. lH NMR data were in about 1%abundance as shown by ESR spectro~copy.~~ referenced to the residual solvent proton resonance unless Treatment of 13%with 2 equiv of CF3COOH resulted otherwise indicated. Microanalyses were performed by Galbraith Laboratories, Inc. Indene and boron trifluoride etherate in 7. In contrast, protonation of Liz[FvMoz(CO)d a t 20 were distilled and stored at -20 "C. Mo(C0)3(py)3,3*w(co)3"C resulted in the neutral metal dihydride complex ( ~ ~ 1and 3 , Cr(C0)3(NH&39 ~ ~ were synthesized according to which decomposed quantitatively to FvMoz(C0)~over published procedures and stored under dinitrogen at -20 "C. a period of 24 h.24 Reaction of 13'a with Diazald gave l,l'-Biindeny140and ferrocenium tetraflu~roborate~l were syn(q5-2-(2'-indenyl)indenyl)Cr(CO)~N0 (ca. 8%). No evithesized according to published procedures. dence of a dichromium compound was seen. 2,2'-Biindenyl (7). 2-Bromo-1-indanol was synthesized Efforts to synthesize hetero bimetallic complexes of according t o ref 42 in 81% yield (lit. 78%). The bromohydrin dibenzo[b,elfulvalenehave so far failed. Double deprowas then dehydrated to 2-bromoindene by an improved version tonation of 14 to give 17'a followed by addition of Feof the procedure found in ref 43: A 1 L round bottom flask (CO)~IZ at -78 "C gives 7'and 16; the analogous was charged with 300 mL of CC14 and 12.64 g (89.0 mmol) of molybdenum dianion 17%, formed from Mo(CO)~and P205. On the neck was fitted a Soxhlet extraction apparatus, the sintered glass thimble of which was charged with 18.94 g doubly deprotonated 7 in refluxing BuzO, reacts simi(89.0 mmol) of the bromohydrin. The CC14 was brought to larly.

16

17'a:M=Cr tXM=Ml

Failure of 13a,b t o form bimetallic complexes analogous t o la,b is puzzling. In contrast to 3'a,b, treatment with oxidizing agents results predominantly in partial or complete demetalation. In conclusion, we have reported the synthesis of novel dibenzo[a,dl- and [affulvalene metal-metal bonded complexes and have compared their structural features with their fulvalene analogues. The benzo rings convey some synthetic advantages arising from the stability of 2 and their role as sites of transient complexation in 3. The molybdenum complex, lb, has shown reactivity differences from its fulvalene analogue consistent with operation of the indenyl effect. More extensive reactivity studies are underway, and the results will be reported in a future paper.

Experimental Section General Procedures. All reactions were performed in flame-dried glassware under a n atmosphere of dinitrogen using double manifold and Schlenk techniques. Carbon tetrachloride was distilled and stored in a tightly sealed bottle. (34) This procedure is a variation of that found in: Birdwhistell, R.; Hackett, P.; Manning, A. R. J. Organomet. Chem. 1978,157,23941. (35) Davis, R.; Kane-Maguire, L. A. P. Chromium Compounds with +-q8 Carbon Ligands. In Comprehensive Organometallic Chemistry Wilkinson, G., Stone, F. G. A., Abel, E. A., Eds.; Pergamon: Oxford, U.K.,1982; Vol. 3, p 961. (36) Synthesis and spectroscopic data: Baienveck, P.; Simmross, U.; Miillen, K. Chem. Ber. 1988,121,2195-2200. We prefer a synthesis based on Nio-induced coupling of 2-bromoindene. (37) Simmross, U.; Miillen, K. Chem. Ber. 1993, 126, 969-73.

reflux, and heating was continued for 21 h. The mixture was then cooled to room temperature and the product filtered through Celite. To the filtrate was added NaZC03 with stirring, followed by anhydrous MgSO4 to dry, and the mixture filtered again. The filtrate was roto-evaporated to give 14.79 g of crude 2-bromoindene which was distilled in Vacuo (0.05 atm), collecting the fraction boiling at 87-112 "C to give 11.02 g (64%) of spectroscopically pure ('H NMR) product. The 2-bromoindene was then homocoupled using the procedure of ref 44: To a 500 mL three-neck round bottom flask equipped with a mechanical stirrer was added 8.87 g (135.7 mmol) of Zn powder, 7.04 g (54.3 mmol) of anhydrous NiC12, 45.06 g (271.4 mmol) of KI, and 250 mL of l-methyl-2pyrrolidinone. The mixture was stirred at 60-65 "C for 1 h aRer which time 26.45 g (135.6 mmol) of 2-bromoindene was added in one portion. Heating was continued for 3 days, after which time the reaction mixture was cooled to room temperature. Approximately 10 mL of 6 N HC1 was cautiously added with stirring. After gas evolution ceased, 150 mL of distilled HzO was added and the mixture transferred to a separatory funnel, to which was added approximately 200 mL of CH2C12. The organic layer was drawn off and filtered through Celite. The precipitate contained undissolved product and had to be washed 10 times more with CHzC12. The combined lightyellow filtrate was roto-evaporated, and 500 mL MeOH was added to the pot residue to precipitate the product which was isolated by a final filtration to give 13.38 g (86%) of microcrystalline, spectroscopicallypure 7. Spectral data agreed with those in ref 36. 5 and 6. Into a stirring solution of 2 (0.620 g, 2.69 mmol) in 25 mL of THF at room temperature was syringed 2.2 mL (5.5 mmol) of a 2.5 M solution of n-BuLi in hexanes; the color of the solution immediately became dark brown. The solution was promptly cooled to -78 "C with a dry ice bath, and Br2 (0.14 mL, 2.73 mmol) was quickly added by syringe resulting in gas evolution and a dark red-brown solution. The dry ice was allowed to sublime overnight after which the reaction was quenched with -10 mL of distilled water and the resulting

(38) Hieber, W.; Miihlbauer, F. 2. Anorg. Allg. Chem. 1936, 221, 337. (39) Razuvaev, G. A.; Artemov, A. N.; Aladjin, A. A.; Sirotkin, N. I. J. Organomet. Chem. 1976, 111, 131-5. (40) Nicolet, P.; Sanchez, J. -Y.; Benaboura, A.; Abadie, M. J. M. Synthesis 1987,202-3. (41) Hendrickson, D. N.; Sohn, Y. S.; Gray, H. B. Inorg. Chem. 1971, 10, 1559. (42) Lindley, W. A.; MacDowell, D. W. H. J . Org. Chem. 1982,47, 705-9. (43) Porter, H. D.; Suter, C. M. J.Am. Chem. SOC.1936,57,2024. (44) Takagi, K.; Mimura, H.; Inokawa, S. Bull. Chem. SOC.Jpn. 1984,57, 3517-22.

Group 6 Complexes of Dibenzofulualenes mixture extracted with -50 mL of CHzC12. The red organic layer was dried with MgS04, filtered, and roto-evaporated. The residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed silica gel (40-140 mesh). The column was eluted consecutively with 200 mL batches of 0, 5, 10,20, and 50%EtzOhexane and EtOAc. The set of fractions eluting in the 0-5% regime contained predominantly 5 and 6 in -1:l ratio, while the fractions eluting in the 10-20% regime contained predominantly 5; later fractions were complex mixtures. The fractions eluting in the 10% regime were, after roto-evaporation, crystallized from hexanelCHCl3, and the resulting crop was recrystallized by slow diffusion of hexane into a saturated CHClfltOAc solution. The overall yields of 5 and 6,determined by integral ratios, were 17% and 18%, respectively. 5: lH NMR (300 MHz, CDZC12) 6 5.64 (s, 2H), 6 5.73 (s, 2H), 6 7.49 (d oft; 1.0 Hz, 7.5 Hz; 2H), 6 7.58 (d oft; 1.3 Hz, 7.6 Hz; 2H), 6 7.63 (d, 7.8 Hz, 2H), 6 7.96 (d, 7.8 Hz, 2H); 13C NMR (62.9 MHz, CDZClz) 6 53.9, 56.0, 126.9, 127.0, 130.6, 131.1, 137.6,137.8,143.6; MS (EI), m l z (based on 79Br) 386 (2) (M - 2Br)+,307 (20) (M - 3Br)+,228 (100) (Cd&)+; dec 180 "C. Anal. Calcd for C~HlzBr4:C, 39.46; H, 2.21. Found: C, 38.17; H, 2.70. 6: 'H NMR (250 MHz, CDC13) 6 5.63 (9, lH), 6 5.86 (s, lH), 6 6.93 (d, 5.6 Hz, lH), 6 7.08 (d, 5.7 Hz, lH), 6 7.3-7.95 (multiplet, 8H). Compound 5 can be consistently synthesized relatively free of 6 and in respectable yield as follows: 2 (0.506 g, 2.20 mmol), n-BuLi (1.8 mL, 4.5 mmol), Brz (0.45 mL, 8.8 mmol), and 25 mL of Et20 as solvent are brought to reaction as above except that the reaction is stopped 5.5 h after the addition of Brz, the dry ice having sublimed by then. The crude mixture is roto-evaporated and the residue washed with distilled H2O (1x 100 mL) and MeOH (2 x 50 mL), and dried with suction t o give 0.803 g (67%) of reasonably pure 5. Synthesis of Dibenzo[a,d]fulvalene. Method 1. Starting with 2.02 g (8.77 mmol) of 2 in 100 mL of EtzO, 5 was synthesized as above. The crude product was obtained by rotoevaporation, and 100 mL of distilled HzO was added to the residue. The aqueous layer was extracted with 200 mL of CHzC12, and the organic layer was dried with anhydrous MgSOa, filtered, and rotoevaporated. The residue was transferred t o a 250 mL round bottom flask equipped with a sidearm and magnetic stirrer; the flask was subsequently degassed with a stream of dinitrogen for 5 min. With the dinitrogen still flowing, 100 mL of acetone was quickly added along with ca. 0.1 g of anhydrous NazC03. The mixture was stirred for 5 min, and then NaI (5.26 g, 35.1 mmol) was quickly added under a stream of dinitrogen. Stirring was continued for 3 h, after which time the reaction mixture was filtered. The flask and funnel were washed with an additional 200 mL of CHC13, and the combined organic layers were extracted with 10% aqueous thiosulfate (1 x 150 mL) and distilled HzO (1 x 100 mL). The organic layer was dried with anhydrous MgS04, filtered, and roto-evaporated over anhydrous Na2C03. The residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed Florisil(60-100 mesh) to give 0.474 g (24%) of reasonably pure [a,dl isomer. Method 2. A 100 mL round bottom flask with sidearm was soaked in base-bath (1liter of 95% EtOH, 120 mL of HzO, 120 g of NaOH) for several min, washed with copious amounts of distilled water, and flame-dried under a stream of dinitrogen. To this flask was added, under a stream of dinitrogen, 1.00 g (4.35 mmol) of 2, 50 mL of EtzO, and a Teflon-coated stir bar. To the stirring solution was added by syringe 3.6 mL (9.0 mmol) of a 2.5 M solution of n-BuLi in hexanes. The reaction mixture was cooled t o -78 "C with a dry ice bath, and Brz (0.23 mL, 4.49 mmol) was quickly added by syringe. The dry ice was allowed to sublime, and the reaction mixture was stirred an additional 2 h at room temperature. An additional 100 mL of Et20 was added, and the organic layer was washed with 10% aqueous sodium thiosulfate (150 mL) and distilled HzO (100 mL). The organic layer was dried with MgS04, filtered, and roto-evaporated over anhydrous Na~C03. The residue was chromatographed on a 15 cm high, 4 cm diameter

Organometallics, Vol. 14, No. 10,1995 4749 bed of hexane-packed silica gel (40-140 mesh, pH = 7) to give 0.506 g (51%)of reasonably pure dibenzo[a,dlfulvalene. Under similar conditions except with THF as solvent, use of 1equiv of 12 (calculated on 2) as the oxidizing agent gave an intractable dark greenish-brown crude product whose lH NMR was very comp1ex. O(,q6:p6-3,S-Biindenyl)cr~(Co)6 (3a). The procedure followed is that of ref 45 . Into a stirring, room-temperature mixture of 1,l'-biindenyl (0.755 g, 3.28 mmol) and Cr(CO)3(NH3)3 (1.85 g, 9.88 mmol) in Et20 (75 mL) was syringed EtzO.BF3 (6 mL, 49 mmol). Stirring was continued for 6 days, during which time the initially yellow reaction mixture was seen to darken with the formation of an orange-brown precipitate and a burgundy solution. The reaction mixture was filtered with suction. The reaction vessel and precipitate from the filtration were washed twice with Et20 and the washings also filtered. The resultant brown precipitate was washed with 1M HCl(2x), distilled HzO (1x1, and MeOH ( l x ) . The washed precipitate, green in color, was first suction dried (-5 min) and then dried in uacuo (-5 min) to give 0.705 g (43%) of 3a. The product at this stage was fairly pure by 'H NMR and was used without further purification. It can be crystallized by pentane diffusion into an EtOAc solution: 'H NMR (250 MHz, DMSO-ds) 6 3.56 (d, 24.9 Hz, 2H), 6 3.84 (d, 24.4 Hz, 2H), 6 5.61 (quasi-triplet, 5.8 Hz, 2H), 6 5.73 (quasi-triplet, 6.1 Hz, 2H), 6 6.20 (d, 6.1 Hz, 2H), 6 6.31 (d, 5.7 Hz, 2H), 6 6.82 (s,2H); 13CNMR (62.9 MHz, DMSO-d6)6 38.7,89.4,92.0, 92.2,93.2, 114.5, 115.3, 133.3, 135.5, 234.2; MS (EI), m l z 502 (9) (M)+,418 (38) (M - 3CO)+,390 (24) (M - 4CO)+,362 (22) (M - 5CO)+,334 (100) (M - 6CO)+,282 (100)(M - GCO-Cr)+, 228 (20) (Cl&Z)+; IR (KBr) 1959 (s), 1870 (s), 663 (w), 631 (w) cm-'; mp 187.5-190 "C. Anal. Calcd for Cr~C~4H1406: Cr, 20.70. Found: Cr, 20.95. (lr,q6~6-3,3-Biindenyl)Moa(CO)s (3b). l,l'-Biindenyl(O.518 g, 2.25 mmol) and Mo(CO)s(py)3(2.83 g, 6.77 mmol) in Et20 (50 mL) were treated with EtzO-BF3 (4.1 mL, 33.3 mmol) as in the preparation of 3a. A color change to a green precipitate and red solution occurred within less than 1 h, but stirring was continued for 6 days. The resultant precipitate was worked up as in the preparation of 3a to give green colored 3b (1.03 g, 78%). An lH NMR of the filtrate obtained by filtering the crude reaction mixture showed 3,3'-biindenyl with no sign of y'komplexed products. If the reaction is run at reflux instead of room temperature, then it may be worked up after only 3 days to give 80% yield: MS (EI), m l z (based on 9 s M ~412 ) (2) (M - Mo(C0)3)+,328 (8)(M - Mo(COM+, 266 (2) (Mo(CO)d+,230 (76) (ClaH14)+,115 (100) (CgH7)+;IR (KBr) 1962 (sh), 1948 (s), 1867 (s), 1844 (SI cm-l; dec '144 "C. [O(,q5:q5-Dibenzo[a,dlfulvalene)Cr~(~O)~]z~ (3'a). 3a (0.04 g, 0.0796 mmol) was dissolved in 1 mL of DMSO&. While the solution stirred, 0.32 mL (0.32 mmol) of a 1M THF solution of t-BuOK was introduced by syringe. The color became dark, and stirring was continued for 5 min. In the meantime, an NMR tube was placed inside a 1L round bottom flask supplied with a vacuum adapter. The setup was evacuated and refilled with dinitrogen. The D M s 0 - d ~solution was then transferred with a syringe to the NMR tube through a rubber septum in the vacuum adapter. The adapter was removed and the NMR tube quickly capped with a rubber septum. A proton NMR was taken within 5 min. The same sample was afterward transferred with a syringe to a degassed IR NaCl cell and a n IR taken: 'H NMR (250 MHz, DMSO-&) 6 4.75 (br s, 2H), 6 5.27 (br s, 2H), 6 6.59 (br s, 4H), 6 7.27 (m, 4H); IR (DMSO-ds) 1886 (s), 1784 (SI, 1755 (sh) cm-'. [~,q5:q5-Dibenzo[a,d]fulvalene)Mo~(CO)dz~ (3%). 3b (0.086 g, 0.146 mmol) was suspended in 5 mL of EtzO. While the solution stirred, 0.58 mL (0.58 mmol) of a 1M THF solution of t-BuOK was introduced by syringe. The color changed instantly from a light green t o a darker brownish-green. (45) Peitz, D. J.; Palmer, R. T.;Radonovich, L. J.; Woolsey, N. Organometallics 1993,12,4580-4.

F.

4750 Organometallics, Vol. 14, No. 10, 1995 Stirring was continued for 10 min after which time 1 mL of DMSO-& was added; the color immediately became greenishblack. The Et20 was then removed in uucuo. The remaining DMSO-& solution was then treated as in the procedure for 3'a. 'H NMR(250 MHz,DMSO-&): 6 5.32 (d, 1.9 Hz,2H), 6 5.76 (d, 1.9 Hz, 2H), 6 6.70 (m, 4H), 6 7.31 (d, 7.8 Hz, 2H), 6 7.63 (d, 7.5 Hz, 2H); these represent the most intense signals. For each such signal there was a corresponding signal slightly upfield one-tenth as intense and similar in overall appearance. These signals are assigned to the dianion of 4: 6 5.23 (br s, 2H), 6 5.68 (br s, 2H), 6 6.25 (m, 4H), 6 7.08 (d, 7.4 Hz, 2H), 6 7.44 (d, 7.0 Hz, 2H); IR (DMSO-&) 1889, 1777 cm-'. ~,~5:~5-Dibenzo[a,dlfulvalene)~r~(~~)~ (la). Method 1. Into a stirring suspension of 3a (0.105 g, 0.209 mmol) in 10 mL of Et20 was syringed 0.44 mL (0.44 mmol) of a 1 M THF solution of t-BuOK without immediate color change. Stirring was continued for 35 min still without change, at which point reflux was begun. Reflux was continued for 45 min after which time the heating mantle was removed and the reaction mixture cooled to -78 "C in a dry ice bath. Ferrocenium tetrafluoroborate (0.114 g, 0.418 mmol) was added quickly and stirring allowed t o continue for an additional 7 h while the dry ice slowly sublimed away. The reaction mixture was roto-evaporated, the residue was washed with CHC13 (3x1, and the washings were discarded. The precipitate was then washed with distilled H2O ( l x ) and MeOH (2x1 and dried with suction. The IR of the green precipitate (0.067 g) indicated a mixture of 3a and la. Compound la was obtained in purer form by a direct thermal route, method 2. Method 2. The procedure is like that given in ref 34. Into a stirring solution of 1,l'-biindenyl(O.496 g, 2.15 mmol) in 25 mL of Bun0 was syringed 1.81 mL (4.53 mmol) of a 2.5 M solution of n-BuLi in hexanes causing the reaction mixture to become a cloudy yellow. Cr(CO)e (1.00 g, 4.55 mmol) was quickly added, and the reaction mixture was subsequently brought to reflux. After 18 min at reflux, the color had become deep green. Cr(CO)6 that sublimed into the condenser was intermittently returned to the flask with 1 mL of washings of BuzO quickly introduced a t the top of the condenser under a flow of dinitrogen. The system was kept at reflux for a total of 70 min after which time the heat was removed. The system was allowed to cool to room temperature and then cooled to -78 "C with a dry ice bath. Ferrocenium tetrafluoroborate (1.17 g, 4.30 mmol) was quickly added and the reaction mixture stirred for 7 h as the dry ice slowly sublimed. The Bun0 was removed in uucuo (the distillate was yellow with ferrocene and also contained some unreacted Cr(CO)6)leaving a pot residue that was dark brown in color. The crude product was dry-loaded onto a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40-140 mesh) and the column eluted consecutively with 200 mL batches of 0, 10, and 20% EtzOhexane, 10%EtOAc/EtzO, EtOAc, 10% CH3CN/Et20, and MeOH. A forerun of ferrocene, dibenzo[u,d]fulvalene, 3 3 biindenyl, and (1-indanylidenel-1-indene eluted in the 10-20% EtzOhexane regime. The later fractions were combined and roto-evaporated. The residue was washed with CHC13 (3x 1. The washings, which were deep red, were shown to contain mainly dibenzo[u,d]fulvalene by IR. The green precipitate was washed (to remove a contaminant giving a strong, broad peak in the IR a t 1084 cm-') with distilled HzO ( l x ) , MeOH (2x), and CHC13 (1x1, the CHC13 washing again being deep red. Washing the precipitate, now more brownish-green in color, with either toluene or acetone also gave deep red filtrates, the red color not diminishing in intensity after repeated washings; only hexane gave a colorless filtrate. Presumably, the red color was due to dibenzofulvalenes which formed as la decomposed upon dissolution. An NMR of the precipitate in DMSO-& showed only dibenzo[u,dlfulvalene. IR (Kl3r): 1997 (s), 1937 (SI, 1919 (sh), 1892 (SI, 747 (w), 604 (w), 574 (w), 552 (w) cm-l. Crude yield: 49% (0.053 g). ~,~5:p5-Dibenzo[a,dlfulvalene)Mo~(CO)~ (lb). Method 1. Into a stirring suspension of 3b (0.729 g, 1.24 mmol) in 50

Kerber a n d Waldbaum mL of Et20 was syringed 2.6 mL (2.6 mmol) of a 1 M THF solution of t-BuOK with immediate color change to deeper green. After being stirred for 30 min, the reaction mixture was cooled to -78 "C with a dry ice bath. Ferrocenium tetrafluoroborate (0.677 g, 2.48 mmol) was quickly added, and stirring was continued for 5 h. The reaction mixture, consisting of a dark brown solution and green precipitate, was then warmed to room temperature and roto-evaporated. The residue was washed with hexane (2x) and CHC13 (3x), and the dark red washings were discarded. The remaining precipitate was washed with distilled HzO (2x1, MeOH (1x1 and Et20 ( l x ) and dried in uacuo to give spectroscopically pure dark bluish-green lb (0.389 g, 53.5%): 'H NMR (300 MHz, CDC13) 6 5.31 (d, 3.3 Hz, 2H), 6 6.50 (d, 3.2 Hz, 2H), 6 6.80 (d, 8.7 Hz, 2H), 6 6.91 (quasi t, 2H), 6 7.10 (quasi t, 2H), 6 7.67 (d, 8.4 Hz, 2H); 13C NMR (62.9 MHz, DMSO-&) 6 82.7, 85.2, 87.0, 106.7, 107.0, 122.5, 124.6, 125.8, 127.4; MS (EI), m l z (based on 9 6 M ~560 ) (9) (M - CO)+, 532 (5) (M - 2CO)+, 504 (13) (M - 3CO)+,476 (39) (M - 4CO)+,448 (20) (M - 5CO)+, 420 (66) (M - 6CO)+,228 (31) (Ci8Hiz)+,226 (100) (CisHio)+, 192 (88) (Moz)+;IR (KBr) 2002 (SI, 1968 (m), 1949 (m), 1930 (m), 1899 (s), 1872 (w); dec >278.5 "C. Anal. Calcd for (224HlzO&Ioz: C, 49.00; H, 2.06; Mo, 32.62. Found: C, 48.28; H, 2.05; Mo, 39.65. Method 2. l,l'-Biindenyl(1.309g, 5.68 mmol), 4.8 mL (12.0 mmol) of a 2.5 M solution of n-BuLi in hexanes, Mo(COI6(3.013 g, 11.4 mmol), and 60 mL of Bu2O were brought to reaction as in the thermal route for la, except that the system was refluxed for only 30 min, and after the addition of ferrocenium tetrafluoroborate (3.12 g, 11.4 mmol), stirring was continued for 21 h. THF was added to the residue from the Bu2O removal and the mixture filtered. The filtrate was roto-evaporated. The precipitate was washed with hexane (2x1, toluene (2x1, distilled H20 (2x 1, and MeOH (2 x 1. The hexane filtrate was shown by 'H NMR to contain predominantly ferrocene and 3,3'-biindenyl with only traces of 4 and lb;likewise, the MeOH filtrate was mostly ferrocene. The MeOH-washed precipitate was spectroscopically pure lb (0.764 g). The toluene filtrate (0.865 g after removal of solvent) contained significant amounts of 4 and lb (-1.7:l) and was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40-140 mesh). The column was eluted consecutively with 200 mL batches of 0, 10,20, and 50% EtzOhexane, and 10% EtOAc/EtzO. A forerun of 3,3'-biindenyl and ferrocene eluted in the 0-20% EtzOhexane regime. Two more sets of fractions followed: the first contained purely 4 and lb (-2.1:1), and the second contained lb and an unknown compound that exhibited a pair of doublets at 6 5.34 and 6.45 ppm with a coupling constant of 3.5 Hz; only a trace of 4 was seen in the baseline. The first set of fractions was rechromatographed on silica with 200 mL batches of 10,20,30,and 50%EtzOhexane and 50% EtOAdhexane. The set of fractions eluting in the 20-50% EtzOhexane regime were combined; they were shown t o contain 4 and lb in a 3.3:l ratio. Three recrystallizations from EtOAc by slow diffusion of pentane yielded crystals suitable for X-ray diffraction. The final yield of 4 before recrystallizations was determined by integral ratios to be 0.16 g (5%); that of lb was 0.84 g (25%). ~,~5:~5-Dibenzo[a,d]fulvalene)W~(CO)~ (IC). The procedure described is modeled after that given in ref 18a. A three-neck flask equipped with a magnetic stirrer was charged with l,l'-biindenyl(O.300 g, 1.30 mmol), W(C0)3(py)3(1.97 g, 3.90 mmol), and BuzO (25 mL). EtzO.BF3 (2.4 mL, 19.5 mmol) was syringed into the stirring reaction mixture; no immediate change was noticed. With an oil bath, the temperature was gradually increased to 65 "C over a 15 min period by which time the color had become brownish-orange. The temperature was maintained between 65 and 75 "C for 2 h more. The BuzO was removed in uucuo. EtOAc was added to the pot residue and the mixture filtered. The precipitate was washed with 1 M HCl, distilled H20, and MeOH and dried in uucuo to give spectroscopically pure IC (0.094 g). The filtrate was washed, in turn, with 1 M HCl and distilled H20. The organic layer

Group 6 Complexes of Dibenzofilualenes was dried with anhydrous MgS04, filtered, and roto-evaporated. The pot residue was dry-loaded onto a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40140 mesh). The column was eluted consecutively with 200 mL portions of 0, 5, 10, 20, 50, and 100% EtOAheptane and finally 200 mL of CH3CN. The fractions eluting from 50% onward were combined and rotoevaporated. The residue was washed with Et20 (2x1 and CHzCl2 (2x1 and the precipitate collected t o give spectroscopically pure dark blue-green IC (0.048 g). The combined yield was 14%. 'H NMR (300 MHz, DMSO-&) 6 6.05 (d, 3.2 Hz, 2H), 6 6.94 (d, 3.2 Hz, 2H), 6 6.98 (t, 7.8 Hz, 2H), 6 7.17 (quasi-triplet, 2H), 6 7.26 (d, 8.8 Hz, 2H), 6 7.81 (d, 8.5 Hz, 2H); 13CNMR (62.9 MHz, DMSO-&) 6 78.7, 81.7, 85.7, 104.1, 104.7, 122.9, 124.8, 126.1, 128.0; FAB MS mlz 764 (1.21, 736 (l.O), 708 (1.1)due to M+ - (0, 1 , 2 CO), based on 184W;IR (KBr) 2000 (s), 1946 (s), 1909 (s), 1887 (9) cm-l; dec >292 "C. (p,q5:q5-Dibenzo[a,flfulvalene)Mo~(CO)~ (4). See preparation of lb,method 2. Note that 4 forms also via method 1 (ca. 4:1, lb to 4)but was not isolated and purified from those runs. 'H NMR (300 MHz, CDC13) 6 4.17 (d, 3.3 Hz, 2H), 6 5.83 (d, 3.3 Hz, 2H), 6 7.14 (t, 7.8 Hz, 2H), 6 7.28 (quasi t; 6.8 Hz, 7.6 Hz; 2H), 6 7.61 (d, 8.8 Hz, 2H), 6 7.74 (d, 8.5 Hz, 2H); 13CNMR (75.5 Hz, CDC13) 6 76.6, 77.0, 77.4, 79.0, 83.7, 86.3, 104.4, 109.4, 124.2, 124.4, 125.2, 127.6, 221.4, 226.7, 231.1; MS (EI), m l z (based on 96Mo)560 (17) (M - CO)+, 532 (10) (M - 2CO)+, 504 (7) (M - 3CO)+, 476 (45) (M - 4CO)+, 448 (55) (M - 5CO)+, 420 (99) (M - 6CO)+,226 (100) (CieHio)+, 192 (76) (Moz)'; IR (KBr) 2006, 1958, 1908 cm-'; dec > 239 "C. Anal. Calcd for C24H120&02: C, 49.00; H, 2.06; Mo, 32.62. Found: C, 48.86; H, 2.23; Mo, 34.50. (p,q5:q5-Dibenzo[a,cZlfulvalene)Cr~(CO)~(NO)~ (15). Into a stirring suspension of 3a (0.397 g, 0.790 mmol) in 25 mL of Et20 cooled with an ice/MeOH bath was syringed 1.6 mL (1.6 mmol) of a 1 M THF solution of t-BuOK. Stirring was continued for a 0.5 h after which time the reaction mixture was cooled with a dry ice bath. Diazald (0.346 g, 1.62 mmol) was quickly added, and stirring was continued for 24 h as the dry ice slowly sublimed. The bluish-purple reaction mixture was then roto-evaporated, and the residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40-140 mesh). The column was eluted with 200 mL batches of 0,5,10,20,50, and 100%EtzOhexane. The fractions eluting in the 0 to 20% regime were combined to give, after removal of solvent, 0.063 g (16%) of fairly pure (lH NMR), red colored 15 which was recrystallized at -20 "C from toluenehexane. 'H NMR (300 MHz, CDCl3) 6 5.54 (d, 2.5 Hz, 2H), 6 6.00 (d, 2.8 Hz, 2H), 6 7.1 (m, 4H), 6 7.5 (m, 4H); 13C NMR (62.9 MHz, acetone-&) 6 78.9,93.5,99.8, 110.5, 112.0, 123.6, 126.8, 127.1, 127.9, 237.3, 238.3; MS (EI), m l z 476 (2) (M - COY, 448 (13)(M - 2CO)+,420 (14) (M - 3CO)+, 392 (3)(M - 4CO)+, 362 (100) (M - 4CO-NO)+,332 (2) (M 4CO-2NO)+,280 (10) (C18HlzCr)+,228 (14) (ClsH12)+,52 (95) (Cr)+;IR(KBr) 2014 (s), 1935 (s), 1698 (s), 748 (m), 624 (m), 464 (w) cm-l; dec >203 "C. (lr,q6:q6-2,2-Biindenyl)Crz(CO)e (13a). 2,Y-Biindenyl, 7 (0.538 g, 2.34 mmol), and Cr(C0)3(NH3)3(1.30 g, 6.96 mmol) were treated with Et20.BF3 (4.3 mL, 35.0 mmol) in Et20 (50 mL) as with 3a. A color change t o a red suspension was apparent within 1h. Stirring was continued for 2 days, and the resultant orange precipitate was worked up as above (including additional washings with CHzClz (2 x ) to eliminate 7 and 14 side products) to give (1.00 g, 85%)13s. The lH NMR of the product showed two isomers of 13a as well as minor contamination from 7 and 14,making the region between 6 3.6 and 4.0 ppm rather complicated. Intentional synthesis of 14 using 1equiv of Cr(CO)3(py)3produced 13a as a side product which was eluted from a silica column with EtOAc, enriched in one isomer and with less 7 contamination. The 'H NMR of the principal isomer (300 MHz, acetone-&, reference TMS) showed 6 3.82 (d, 22.5 Hz, 2H), 6 3.97 (d, 22.2 Hz,2H), 6 5.51 (4,6.6 Hz, 2H), 6 5.61 (q, 5.9 Hz, 2H), 6 6.11 (m, 4H), 6 6.84 (s, 2H); MS (EI), m l z 502 (0.2) (MI+, 446 (0.4) (M - 2CO)+,

Organometallics, Vol. 14, No. 10, 1995 4751 418 (0.6) (M - 3CO)+, 362 (0.4) (M - 5CO)+, 334 (2) (M 6CO)+,282 (4) (M - GCO-Cr)+,230 (3) (C18H14)+,52 (100) (Cr)+; IR (KJ3r) 1960 (81, 1889 (SI, 1847 ( 4 , 8 3 9 (w), 668 (m), 629 (m), 521 (w) cm-'; dec >274 "C. Only the AB patterns for the CH2 groups are resolvable in the lH NMR of a sample containing both isomers in comparable amounts: lH NMR (250 MHz, DMSO-&) 6 3.65 (d, 22.9, 2H), 6 3.70 (d, 22.5 Hz, 2H), 6 3.91 (d, 25 Hz, 2H), 6 3.97 (d, 22.4 Hz, 2H). (p,q6:q6-2,2-Biindenyl)Moz(CO)e (13b). 7 (0.507 g, 2.20 mmol) and Mo(C0)3(py)3(2.80 g, 6.70 mmol) were treated with Et20BF3 (4 mL, 32.5 mmol) in Et20 (50 mL) as with 3a. Stirring was continued for 2 h, and the resultant orange precipitate worked up as above to give (1.15 g, 88%)13b: IR (KBr) 1954 (s), 1846 (s), 836 (w),619 (w), 587 (w),495 (w) cm-l; dec >170 "C. [(lr,q5:q5-Dibenzo[bplfulvalene)Crz(CO)~lz(13a). About 20 mg of 13a was dissolved in 1.5 mL of DMSO-& under dinitrogen. While the solution stirred, an excess of solid t-BuOK was quickly added resulting in a rapid color change to dark brown. The solution was stirred for 5 min before being transferred by syringe to an evacuated NMR tube equipped with a 24/40 joint; the bottom portion of the tube was immersed in liquid dinitrogen during the transfer. The tube was sealed with a torch, and the NMR was taken 10 min after the transfer. lH NMR (300 MHz, DMSO-&): 6 5.07 (s, 4H), 6 6.5 (m, 4H), 6 7.2 (m, 4H). An IR sample was prepared as follows: To a stirring suspension of 13a (0.206 g, 0.410 mmol) in 20 mL of THF was quickly added solid t-BuOK (0.098 g, 0.873 mmol) with no immediate color change. The reaction mixture was warmed to -40 "C for 26 min during which time the color became yellow. A 1 mL aliquot was removed by syringe and injected into a degassed NaCl IR cell: IR (THF) 1961,1895,1794, 1754 cm-'. [~,~~:~~-Dibenzo[bplfulvalene)Mo~(CO)~l~~ (13%). Into a stirring suspension of 13b (0.05 g, 0.0847 mmol) in 10 mL of Et20 was syringed 0.17 mL (0.17 mmol) of a 1 M THF solution of t-BuOK. Within 20 min at room temperature, the color had become yellow. DMSO-& (1mL) was then added by syringe, and the Et20 was removed in uucuo. The residual solution was then transferred to an NMR tube as in the procedure for 3'a: 'H NMR (250 MHz, DMSO-&) 6 5.68 (s, 4H), 6 6.58 (dd; 2.8 Hz, 6.3 Hz; 4H), 6 7.26 (dd; 2.6 Hz, 6.2 Hz; 4H). [(t15-2-(2'-Indenyl)indenyl)Mo(CO)&(12). Into a stirring suspension of 13b (0.219 g, 0.371 mmol) in 25 mL of Et20 was syringed 0.77 mL (0.77 mmol) of a 1 M THF solution of t-BuOK. Within 25 min, a color change to yellow had occurred, and the reaction mixture was cooled to -78 "C in a dry ice bath. Ferrocenium tetrafluoroborate (0.202 g, 0.740 mmol) was added quickly, and 5 min afterward the dry ice was removed, at which point the reaction mixture was green in color. Within 25 min, the color had become brown, and the reaction vessel was covered in aluminum foil. Three hours later, the color was blackish-purple; 2 h thereafter, the reaction mixture was roto-evaporated. The residue was dry-loadedonto a 15 cm high, 4 cm diameter bed of hexane-packed, degassed alumina (80-200 mesh) which had been dried at 100 "C in uacuo overnight, The column was eluted with 200 mL portions of 0, 10,50, and 100% CH~Clz/hexane.A forerun of ferrocene eluted in the 50%regime followed by 12 (0.014 g, 9%) in the 100% regime: 'H NMR (250 MHz, CDC13) 6 3.72 (s, 4H), 6 5.17 ( 8 , 4H), 6 6.91 (s, 2H), 6 7.05 (m, 4H), 6 7.15 (d oft; 1.3 Hz, 7.3 Hz; 2H), 6 7.22 (m, 6H), 6 7.34 (d, 7.5 Hz, 2H), 6 7.42 (d, 7.3 Hz, 2H); 13CNMR (75.5 MHz, CDCld 6 38.7, 77.6,93.7, 106.3, 120.9, 123.7, 124.6, 125.0, 126.4, 126.7, 128.0, 143.0, 143.5, 145.4, 229.8; IR (KBr) 1996, 1950, 1921, 1896 (with shoulder on left) cm-'; dec >230 "C. 8-10. 2 (0.608 g, 2.64 mmol), Cr(C0)3(NH3)3(1.48 g, 8.01 mmol), Et20BF3 (4.8 mL, 39.0 mmol), and 50 mL of Et20 were brought to reaction as above t o give 0.462 g (35%)of 3a. The filtrate that resulted from filtering the crude reaction mixture was washed with 1 M HCl(aq) and distilled HzO, dried with anhydrous MgS04,filtered, and roto-evaporated. The residue

4752

Organometallics, Vol. 14, No. 10, 1995

Kerber and Waldbaum

6 5.57 (d o f t ; 1.1Hz, 6.4 Hz; 1H); 6 6.05 (d, 6.0 Hz,lH), 6 was chromatographed on a 15 cm high, 4 cm diameter bed of 6.12 (d, 6.8 Hz, lH), 6 6.74 (s, lH), 6 7.08 (s, lH), 6 7.21 (m, hexane-packed, degassed florisil(60-100 mesh) using 200 mL 2H) (here, overlap with the signals for 7 prevented more batches of 0,5,10,20, and 50% EtzOhexane, 10%EtOAdEtzO, detailed analysis of the pattern), 6 7.39 (d, 6.8 Hz, lH), 6 7.44 and EtOAc. The fractions eluting in the 0-20% regime (d, 6.8 Hz, 1H); MS (EI), m l z 310 (2) (M - 2CO)+,282 (19) (M contained predominantly 3,3'-biindenyl. The fractions eluting - 3CO)+,230 (8)(ClsH14)+,52 (100)(Cr)+;IR (NaC1) 1950, 1865 in the 20-50% regime contained predominantly 10: 'H NMR cm-'; dec '175 "C. (250 MHz, acetone-&) 6 3.60 (s, 2H), 6 3.64 (d, 24.4 Hz, l H ) , 6 3.87 (d, 24.4 Hz, lH), 6 5.55 (t, 6.3 Hz, 6.2 Hz, lH), 6 5.67 (t, Reaction of 13'a with Diazald. 13a (0.412 g, 0.820 6.5 Hz, l H ) , 6 6.16 (d, 6.3 Hz, lH), 6 6.24 (d, 6.2 Hz, lH), 6 mmol), t-BuOK (1.6 mL, 1.6 mmol), Diazald (0.356 g, 1.66 6.87 (s, lH), 6 6.88 (s, lH), 6 7.27 (t,7.3 Hz, lH), 6 7.34 (quasi mmol), and 25 mL of Et20 were combined as above except (a) t, lH), 6 7.57 (d, 7.2 Hz, lH), 6 7.62 (d, 7.1 Hz, 1H); IR (KBr) a n ice/MeOH bath was not used during deprotonation, (b) the 1957 (s), 1875 (s),665 (w), 630 (w) cm-l. The fractions eluting reaction mixture was stirred for 1.5 h after addition of t-BuOK, in the 50% Et20 to 10% EtOAc regime contained a mixture of and (c) the reaction mixture was stirred for 7 h after the 10 and 8 in a 3:l ratio. The yields of 10 and 8 as determined addition of Diazald. The reaction mixture was roto-evaporated by integral ratios were 0.065 g (6.8%) and 0.019 g (1.4%). 8: and the residue chromatographed on a 15 cm high, 4 cm 'H NMR (250 MHz, acetone-&) 6 2.9 (m, 8H), 6 5.64 (t, 6.3 diameter bed of hexane-packed, degassed silica gel (40- 140 Hz, 2H), 6 5.85 (d, 6.4 Hz, 2H), 6 6.39 (d, 6.6 Hz, 2H); other mesh). The column was eluted with 200 mL batches of 0, 5, resonance buried under signals for 10 between 5.4 and 5.6 10,20,50, and 100% EtOAdcyclohexane, and the first eleven fractions (28 mL each) were combined and roto-evaporated. ppm. The fractions eluting in the 10% EtOAc regime contained predominantly 3a (0.202 g). The last set of fractions An 'H NMR of the residue indicated a mixture of 7 and (v5contained predominantly 9: These fractions, after roto2-(2'-indenyl)indenyl)Cr(CO)zNO (singlets at 6 3.55 and 5.8 evaporation, were recrystallized by slow diffusion of pentane ppm in a 1:l ratio were attributed to the -CHz group and the into a saturated EtOAc solution to give 0.032 g (2.4%)of 9. 'H complexed five-membered ring protons of the latter, respecNMR (300 MHz, CDC13) 6 2.6-3.0 (m, 5H), 6 3.65 (d of d; 1 tively) as well as some other minor unidentified contaminants. Hz, 6.8 Hz; 2H), 6 5.24 (m, 2H), 6 5.34 (quasi t, lH), 6 5.43 The MS and IR of the residue are reported: MS (EI), m / z 367 (m, 2H), 6 5.85 (quasi t, 2H), 6 6.35 (d, 6.6 Hz, lH), 6 6.69 (s, (6) (M)+,339 (34) (M - COY, 311 (73) (M - 2CO)+,281 (100) 1H); I3C NMR (62.9 MHz, CDC13)(unprotonated and carbonyl (M - 2CO - NO)+, 230 (100) (ClsH14)+,229 (60) (M - 2CO carbons not seen) 6 29.3,30.5,33.4,38.7,87.4,88.7,88.9,89.7, NO - Cr)+, 52 (100) (Cr)+;IR (KBr) 2016 (s), 1945 (s), 1686 90.1, 90.2, 90.8, 92.5, 135.0; IR (KBr) 1947 (SI, 1860 (s), 667 (s), 751 (w), 627 (w) cm-'. (w), 628 (w) cm-'. Reaction of 13'a with CuC12. To a stirring, room temperature ~,~5:~5-Dibenzo[a~]~lvalene)Mo~(CO (11). )~P(OC ~ ) ~ suspension of 13s (0.206 g, 0.410 mmol) in 20 mL of A stirring, degassed solution of l b (0.093 g, 0.158 mmol) and THF was quickly added under a stream of dinitrogen solid t-BuOK (0.098 g, 0.873 mmol). Stirring was continued for 7 P(OCH& (0.075 mL, 0.636 mmol) in 50 mL of THF was min after which time the reaction mixture was heated to -40 irradiated at 300 nm in a Rayonet photochemical reactor for "C with an oil bath. Within 20 min, the color of the mixture 3 days. The reaction mixture was then roto-evaporated, and had become yellow-orange. One and one half hours thereafter, the residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40-140 anhydrous CuClp (0.116 g, 0.863 mmol) was added quickly under a stream of dinitrogen. Stirring was continued for 20 mesh). The column was eluted with 200 mL portions of 0, 5, min after which time the reaction mixture was cooled to room 10, and 20% EtOAchexane. A forerun of dibenzo[a,dlfulvalene temperature and roto-evaporated. An IR (KBr) of the residue and P(OCH3)3eluted in the 0-10% regime. This was followed by two more sets of fractions, the first set composed of 11 and indicated the presence of 7; in addition, weak signals at 1979, 1958, 1926, and 1880 cm-I were seen. CHzC12 was added to l b in approximately 2.7:l ratio while the second set contained the crude, and the organic layer was washed with distilled 11 and l b in approximately 9:l ratio. The overall yield of 11 HzO. The HzO layer was colorless while the organic layer determined by integral ratios was 29% (0.031 g). The product consisted of an orange solution with a suspended red material; from the second set of fractions was recrystallized by diffusion the suspended material quickly became green in the separaof pentane into a saturated THF solution: 'H NMR (300 MHz, tory funnel. The organic layer was drawn off, the green CDC13) 6 3.59 (d, 11.4 Hz, 9H), 6 5.20 (d, 3.4 Hz, lH), 6 5.35 material filtered, and the filtrate dried over anhydrous MgS04. (d, 3.3 Hz, lH), 6 6.23 (d of d; 3.5 Hz, 6.6 Hz; lH), 6 6.42 (d, The filtrate was roto-evaporated, and an IR (KBr)was taken 3.2 Hz, lH), 6 6.8-7.1 (m, 6H), 6 7.55 (d, 8.4 Hz, lH), 6 7.65 of the residue as well as of the green precipitate. That of the (d, 8.4 Hz, 1H); MS (EI), m / z (based on 96Mo)656 (7) (M green precipitate showed the presence of mostly HzO along CO)+,600 (9) (M - 3CO)+,572 (4) (M - 4CO)+,544 (19) (M with a medium-intensity signal at 513 cm-I; that of the residue 5CO)+, 529 (17) (M - 5CO - CH3)+, 482 (13) (M - 5CO showed the presence of 7 as well as medium-intensity signals 20CH3)+, 451 (17) (M - 5CO - 30CH3)+, 420 (14) (ClsH12Mo~)+, 228 (49) (ClsH12)+,192 (15) (Mop)+,93 (100) (P(OCH~)Z)+; at 1958 and 1879 cm-'. The 'H NMR of the residue showed mainly 7. IR (KBr) 1977 (s), 1924 (s), 1895 (s), 1875 (s), 1828 (m), 1020 (m), 741 (m), 540 (w) cm-l; dec 237.5 "C. Reaction of 13'a with Br2. To a stirring, room-temperature suspension of Ha (0.194 g, 0.386 mmol) in 20 mL of THF (qW)Cr(C0)3(14). 7 (0.518 g, 2.25 mmol) and Cr(C0hwas quickly added under a stream of dinitrogen solid t-BuOK (NH& (0.508 g , 2.71 mmol) were treated with EtzO-BF3 (2.1 (0.087 g, 0.775 mmol). The reaction mixture was warmed t o mL, 17.1 mmol) in Et20 (50 mL) as with 3a. Stirring was -40 "C, and stirring was continued for 35 min, after which continued for 2 days after which time CHpClp was added. The time the color had become light orange. The reaction flask reaction mixture was washed, in turn, with 1 M HC1 and was then covered in aluminum foil and cooled to -78 "C with distilled HzO. The orange organic layer was dried with a dry ice bath. Brp (0.020 mL, 0.390 mmol) was added via MgS04,filtered, and roto-evaporated. The crude product was syringe. The dry ice was removed, and stirring was continued dry-loaded onto a 15 cm high, 4 cm diameter bed of hexanefor 2 h and 40 min. The reaction mixture was then rotopacked, degassed silica gel (40-140 mesh) which had been evaporated, and an IR (KBr) were taken of the residue. The dried at 100 "C in uucuo overnight. After elution of a forerun IR showed the presence of 7 as well as weak signals at 1979, of 7, the product, orange in color, began t o elute with 200 mL 1958,1926, and 1880 cm-'. CHzClz was added to the residue, of 20% EtzO/hexane. After an additional 200 mL of 50%EtzO/ resulting in a brown solution with a green precipitate. The hexane followed by 200 mL of 10% EtOAdEtzO, it had precipitate was filtered off and dried with suction to give 0.145 completely eluted. As it could not be gotten entirely free of 7, g. An IR (KBr) of the precipitate showed the presence of H2O a yield of 0.39 g (48%) was determined by integral ratios: 'H along with medium-intensity signals at 1475 and 512 cm-l. NMR (250 MHz, acetone-&) 6 3.71 (s, 2H), 6 3.83 (d, 22.0 Hz, The CHzClz filtrate was washed with distilled HzO, dried with lH), 6 4.01 (d, 22.5 Hz, lH), 6 5.49 (d oft; 1 Hz, 6.4 Hz; lH),

Group 6 Complexes of Dibenzofilvalenes anhydrous MgS04, filtered, and roto-evaporated. The residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40- 140 mesh). The column was eluted with 200 mL batches of 10% and 100% EtzOhexane. The first three fractions eluting in the 10% regime were combined and roto-evaporated to give a residue weighing 0.013 g; an 'H NMR showed it to be fairly pure 7. The latter four fractions in the same regime were combined and roto-evaporated to give a residue weighing 0.029 g. It gave an 'H NMR characteristic of a complex mixture; however, the in a 5:l ratio presence of 7 and l-hydroxy-2-(2'-indenyl)-indene was confirmed by MS. The origin of the l-hydroxy-2-(2'indeny1)-indene is unclear. It has also been isolated from the reaction of doubly-deprotonated 7 with FeCl&THF, as well as from the reaction of 13% with iodine. l-Hydroxy-2(2'4ndenyl)indene: lH NMR (250 MHz, CDC13) 6 3.63 (d, 22.5 Hz, lH), S 3.75 (d, 21.5 Hz, lH), 6 5.39 ( 6 , lH), 6 6.75 (s, lH), 6 7.17-7.44 (m, 8H), 6 7.53 (d, 6.3 Hz, 1H); MS (EI), m l z 246 (79) (MI+,229 (56) (M - OH)+,228 (53) (M - H2O)+,215 (40), 202 (33),131 (47) (CsH,O)+, 115 (100) (CgH,)+; IR (KBr) 1461 (m), 1390 (m), 844 (m), 750 (s, with shoulder at lower frequency), 717 (m) cm-l. Mp: sample darkened at 160.5 "C and liquefied with further darkening at 186-191 "C. Lack of material prevented further analysis. The last two fractions in the 100% regime gave, after roto-evaporation, a residue weighing 0.015 g. The 'H NMR was characteristic of a complex mixture, but l-hydroxy-2-(2'-indenyl)indene could again be identified. Reaction of 13'a with 1,2-Dibromoethane. To a stirring suspension of 13a (0.202 g, 0.402 mmol) in 20 mL of Et20 was quickly added under a stream of dinitrogen solid t-BuOK (O.lOlg, 0.900 mmol). The mixture was then heated at reflux 40 min, after which time the reaction flask was wrapped in aluminum foil and the temperature lowered to -78 "C with a dry ice bath. 1,2-Dibromoethane (35 pL, 0.406 mmol) was then added via syringe, and stirring was continued for 18 h. The reaction mixture was roto-evaporated, and the residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed alumina (80-200 mesh). The column was eluted with 200 mL batches of 0,20,40, and 100% dichloroethanehexane, and EtOAc. The fractions eluting in the 40% regime consisted of 0.028 g (30%) of fairly pure 7. The fractions eluting with 100% dichloroethane contained mainly 14 (0.035 g, 24%). The last set of fractions contained 0.011 g of less pure 14. Reaction of 13a with 12. Into a stirring suspension of 3a (0.277 g, 0.551 mmol) in 20 mL of Et20 was syringed 1.2 mL (1.2 mmol) of a 1 M THF solution of t-BuOK. The reaction mixture was heated a t reflux for 20 min, after which time the reaction flask was wrapped in aluminum foil, and the temperature was lowered to -78 "C with a dry ice bath. Over a 5 min period, a solution of 1 2 (0.142 g, 0.559 mmol) in 20 mL of Et20 was added with a dropping funnel. The reaction mixture was stirred for 15 min at -78 "C. The dry ice was then removed and stirring continued until the reaction mixture reached ambient temperature. The dark purple mixture was roto-evaporated, and the residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40-140 mesh). The column was eluted with 200 mL batches of 0, 20, and 50% EtzOhexane and 10% EtOAd EtzO. The residue from roto-evaporating the fractions eluting in the 0-20% regime was of negligible weight and was shown by 'H NMR t o consist of 7 and 16 in a 7:2 ratio. The residue (0.003 g) from roto-evaporating the fractions eluting in the 2050% regime also showed lH NMR signals for 7 and 14 in a complex mixture. An MS of these fractions confirmed the presence of 7, 16, and 14. In addition, a peak at mass 510 amu was tentatively assigned to one or more complexes of the type (~7~-16)Cr(CO)3. The residue (0.006 g) from roto-evaporating a later set of fractions eluting in the 50% regime gave an lH NMR complicated by line broadening possibly due t o paramagnetic impurities. A MS showed the presence of 7,14, and l-hydroxy-2-(2'-indenyl)indene.The residue (0.048 g) from

Organometallics, Vol. 14,No. 10,1995 4753 roto-evaporating the last set of fractions gave an lH NMR that was severely distorted by line-broadening. An MS showed the presence of 7, 14, l-hydroxy-2-(2'-indenyl)indene,and 16. Reaction of 13a with Ferrocenium Fluoroborate. Into a stirring suspension of 3a (0.238 g, 0.474 mmol) in 25 mL of THF was syringed 0.98 mL (0.98 mmol) of a 1M THF solution of t-BuOK. The reaction mixture was heated at reflux for 40 min after which time the reaction flask was wrapped in aluminum foil and the temperature lowered to -78 "C with a dry ice bath. Ferrocenium fluoroborate (0.266 g, 0.975 mmol) was quickly added under a stream of dinitrogen, and stirring was continued for 19 h as the dry ice sublimed. The dark red reaction mixture was roto-evaporated, and a n lH NMR and IR of the residue were taken. lH NMR (250 MHz, CDC13) (all signals very broad): 6 3.8 (br s), 6 4.2 (br s, ferrocene), 6 5.1 (br s), 7.0 (br s), 7.1-7.6 (br m). The singlet at 3.8 ppm was presumably due to both the chromium dimer (analogue of 12) and 7, so a n integral was not meaningful. IR (KBr): 1993 (s), 1943 (s), 1918 (s), 1909 (s), 1898 (sh), 1872 (m), 1106 (m), 1084 (s), 861 (w), 816 (m), 739 (m), 578 (m) cm-l (the 1106 and 1084 cm-l are presumably due to BF4-). The residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed alumina (80-200 mesh). The column was eluted with 200 mL batches of 0, 50, and 100% CH2C12/ hexane. All fractions eluting in the 0-50% regime consisted of 7 and ferrocene. The last three fractions consisted of l-hydroxy-2-(2'-indenyl)indene(0.007 g, 6%). Reaction of 13%with CFsCOOH. To a stirring suspension of 13b (0.226 g, 0.383 mmol) in 25 mL of Et20 was syringed 0.8 mL (0.8 mmol) of a 1M THF solution of t-BuOK. Stirring was continued for 35 min until the color had become light yellowish-orange. The temperature was lowered t o -78 "C with a dry ice bath, and CF&OOH (62 pL, 0.80 mmol) was added by syringe. After 15 min, the dry ice was removed, and the reaction flask was wrapped in aluminum foil. When it had reached ambient temperature, the brownish-yellow reaction mixture was roto-evaporated, and a n IR was taken of the residue; it showed the presence of 7 along with very weak signals at 1979 and 1954 cm-l. An lH NMR showed essentially pure 7. The crude reaction mixture was washed with CHzClz (3x ) to remove 7 (0.086 g, 98%). The remaining dark brown precipitate (0.12 g), which was insoluble in acetone, MeOH, and HzO, gave the following IR (KBr): 1709 (s), 1420 (m), 1365 (s), 1205 (s), 1138 (m), 967 (w), 838 (w), 804 (w), 723 (w), 534 (w) cm-l. Reaction of [(?6-CeHe-CeHe)Cr(CO)s12-(17'a) and Fe(CO)&. To a stirring solution of 14 (0.440 g, 1.20 mmol) in 40 mL of THF was syringed 2.5 mL (2.5 mmol) of a 1M THF solution of t-BuOK, resulting in immediate color change to dark brown. The reaction mixture was heated at -40 "C for 40 min with an oil bath, after which time the temperature was lowered to -78 "C with a dry ice bath. With a dropping funnel, a solution of Fe(CO)& (0.508 g, 1.20 mmol) in 15 mL THF was added over a 4 min period. After the addition was complete, the reaction mixture was held at -78 "C for 5 min, and then the dry ice was removed. When the dark maroon reaction mixture had reached ambient temperature, distilled H2O (100 mL) followed by CHzCl2 (100 mL) was added. This resulted in an emulsion which gradually broke over 30 min to give a very light green aqueous layer and a brownish-green organic layer. The organic layer was separated, dried over anhydrous MgS04, filtered, and roto-evaporated. An IR of the residue showed very weak 2033,1939, and 1878 cm-' signals. The residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40- 140 mesh). The column was eluted with 200 mL batches of 0, 5, 10, and 100%Et20/hexane. The residue from roto-evaporating the set of fractions eluting in the 5-10% regime weighed 0.131 g and contained 7 and 16 in a 2.1:l ratio. The residue from roto-evaporating the set of fractions eluting in the 10-100% regime weighed 0.010 g and exhibited a more complex 'H NMR that was distorted by line-broadening; however, 7 and 16 in a 0.8:l ratio could be identified. The residue from roto-evaporat-

4754

Kerber and Waldbaum

Organometallics, Vol. 14, No. 10, 1995

Table 7. Crystallographic Data for Compounds 3a, 4,6, and 11 formula cryst colorhabit cryst size, mm space group a, A b, A C,

A

a,deg

A deg

D(calc),g cm-3 diffractometer radiation (graphite monochromator) temp p , cm-1 2 0 range, deg abs corr reflcns collcd indept reflcns obsd reflcns min. max abs R(Fj,RdF), %

Cz4H14Crz06,3a yellow-orange not recorded C2lc 12.438(3) 16.186(2) 10.732(2) 90 107.49(1) 90 2060.6(8) 4 1.617

Cz4HizMozOs, 4 brown 0.2 x 0.2 x 0.4 CWC 21.40(2) 18.69(2) 13.71(1) 90 130.11(3) 90 4194(12)

CleHlzBr4, 6 brown

CzsHziMozOeP, 11 dark green

0.075 x 0.4 x 0.4

0.2 x 0.2 x 0.8 Pbca 29.028(3) 14.502(2) 12.052(1) 90 90 90 5073.5(19) 8 1.7916

P2 lln

1.863

9.003(3) 17.881(2) 10.857(3) 90 93.18(1) 90 1744.8(8) 4 2.0856

Enraf-Nonius CAD-4 Mo Ka (1= 0.710 73)

Enraf-Nonius CAD-4 Mo Ka (1= 0.710 73)

Enraf-Nonius CAD-4 Mo Ka (1 = 0.710 73)

Enraf-Nonius CAD-4 Mo Ka (1= 0.710 73)

ambient

ambient

ambient

ambient

10.656 0 < 2 0 < 50 DIFABS 1615 1500 681 0.9183. 1.0722 3.6,3.6

12.055 0 < 2 0 < 52 DIFABS 4495 4270 2020 0.7574. 1.1504 7.9, 8.4

91.315 0 < 2 0 < 54 DIFABS 3018 2775 1536 3142. 1.0706 6.1, 6.8

10.744 0 < 2 0 < 56 DIFABS 6770 6767 3035 0.9058, 1.0386 3.74,3:60

8

ing the last set of fractions in the 100% regime weighed 0.040 g; it gave an lH NMR that was severely distorted by linebroadening, but 16 could tentatively be identified. The IR spectra of all three sets of fractions showed medium to weak 2028 and 1983 cm-l consistent with the presence of a trace of q5-CrlCO)J type product(s). Reaction of [(115-C~Hs-C~Hs)Mo(C0)932(17%) with Fe(CO)&. Into a stirring suspension of 7 (0.500 g, 2.17 mmol) and Mo(CO)e (0.574 g, 2.17 mmol) in 25 mL of BuzO was syringed 1.75 mL (4.38 mmol) of a 2.5 M solution of n-BuLi in hexanes. The reaction mixture was heated at reflux for 40 min, after which time it was cooled to -78 "C with a dry ice bath. Fe(CO)& (0.926 g, 2.20 mmol) was added quickly under a stream of dinitrogen, and the reaction mixture was allowed to stir for 14 h as the dry ice sublimed. The BuzO was removed in vacuo, and the residue was chromatographed on a 15 cm high, 4 cm diameter bed of hexane-packed, degassed silica gel (40-140 mesh). The column was eluted with 200 mL batches of 0, 5, 10, 20, and 100% EtOAchexane. The residue from roto-evaporating the fractions eluting in the 10% regime weighed 0.114 g and contained predominantly 7 and 16 in a 1.7:l ratio. The residue resulting from roto-evaporating the fractions eluting in the 20 to 100% regime weighed 0.194 g and gave a n lH NMR characteristic of a complex mixture; however, the presence of 7 was confirmed by IR. In addition, the IR exhibited strong peaks at 2028 and 1949 cm-l, consistent with the presence of 175-Mo(C0)31type product(s). Recrystallization efforts afforded 7. The residue from rotoevaporating the last set of fractions weighed 0.073 g and gave a n lH NMR that was distorted by line-broadening. The IR showed medium-intensity peaks at 2030 and 1964 cm-l. X-ray Diffraction Analysis of 3a, 4, 5, and 11. Data collection for all four structures began with a random search a t low 8 to yield 25 reflections which were indexed t o give an initial unit cell. An accurate cell was obtained using higher angle (8= 10-12") reflections. For 3a, 4,and 11,initial direct methods solution (either MITHRIL or SHELXS) revealed the metals and most of the other heavy atoms. A difference Fourier map then yielded the remaining heavy atoms. After partial refinement, hydrogen atom positions were calculated, and the structure was subjected to full anisotropic refinement

of the heavy atoms using full-matrix least squares. A DIFABS absorption correction was applied, and the structure was refined with five more cycles of least squares. In the case of 5, initial S H E D solution revealed some of the carbon skeleton. A difference Fourier map revealed the four bromines. The structure was then subjected to leastsquares refinement after which the remainder of the carbon skeleton was located, followed by another three cycles of least squares. The atoms were then flagged anisotropic, three cycles of least squares were performed, a DIFABS correction was applied, another three cycles of least squares were performed, the hydrogen positions were calculated, and finally, five cycles of least squares were performed, after which two carbons remained non-positive-definite

Acknowledgment. We thank Mr. David Nellis for mounting the crystals and acquiring the data sets. We are also grateful to Prof. K. P. C . Vollhardt for supplying us with crystallographic coordinates for (~4,7~:q~-fulvalene)W(C0)3Rh(CO)C(O)CHg for use in the correlation. B.W. is a recipient of a G A A " fellowship.

Note added in prooE (Dibenzo[b,elfulvalene)Mo~((20)s does form in reaction of 13% and FcH+. The spectroscopic data reported herein for 12 are due t o an equimolar mixture of 7 and the dibenzofulvalene complex. Supporting Information Available: ORTEP structures, packing diagrams, and tables of least-squares planes, important intermolecular contacts, complete positional and isotropic and anisotropic thermal parameters, and bond lengths and angles for compounds 3a, 4,and 11 (65 pages). This material is contained in many libraries on microfiche, immediately follows this article in the microfilm version of the journal, can be ordered from the ACS, and can be downloaded from the Internet; see any current masthead page for ordering information and Internet access instructions. OM950348G