2837
Inorg. Chem. 1989, 28, 2831-2846
Contribution from the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 021 39
Bimetallic Complexes Containing the Bis( tetramethylcyclopentadieny1)ethane Ligand John
F. B u z i n k a i and R i c h a r d R. S c h r o c k *
Received December 12, I988 Heterobimetallic complexes containing the q5,~5-Me4C5CH2CH2C5Me4 ligand (Cp2)can be prepared in which one ring is bound to tungsten and the other is bound to rhodium or cobalt. [WCl4](Cp2)[RhCI2] was prepared by treating the tungstacyclobutadiene complex W(C3Me3)CI3(1)with 1.5 equiv of RhCl2($-Me4CSCH2CH2CgMe)followed by addition of 1 equiv of PC15. Addition of [W(PMe3)C14](Cp2) [Rh(PMe3)CI2]to excess LiA1H4 followed by treatment with methanol yields [W(PMe3)H5](Cp2) [Rh( 6 ) . Addition of 1 equiv of (PMe3)H2],which upon reaction with CO at 1000 psi yields [W(PMe3)H5](Cp2)[Rh(CO)(PMe3)] Me1 to 6 yields [W(PMe3)H5](Cp2)[Rh(COMe)I(PMe3)]. Treatment of 6 with 1 equiv of MeOS02CF3 yields [W(PMe,)H,](Cp2){[RhMe(CO)(PMe3)][OTfl], while treatment with excess MeOTf yields [WH3(OTf'),(PMe3)](Cp2)([RhMe(CO)(PMe,)] [OTflI (8).Treatment of 8 with 1 equiv of NaI yields [WH3(OTf)2(PMe3)](Cp2)[Rh(COMe)I(PMe3)]. Reaction of 1 with 1.5 equiv of 1-(3-pentynyl)-2,3,4,5-tetramethylcyclopntadieneyields [WC14](q5-Me4C5CH2CH2C5Me4H) (11). Addition of 4 equiv of MeMgCl to 11 yields [WMe4]($-Me4C5CH2CH2C5Me4H)(12)while carbonylation produces [WMe(CO),]($(13). Addition of C O ~ ( C Oto) ~13 in neat tert-butylethylene yields [WMe(CO)3](Cp2)[Co(C0)2](14). Me4C5CH2CH2C5Me4H) [WC14](Cp2)[WMe(C0)3] (17)is prepared by treating W(C3Me3)CI3with 1.5 equiv of [WMe(CO)3](qS-Me4C5CH2CH2C= CMe). Addition of 17 to 4 equiv of MeMgCl yields [WMe4](Cp2)[WMe(CO),],which can be selectively oxidized to IWMe41 [pF,l)(Cp2)[WMe(CO)31.
Introduction Known homogeneous processes for the catalytic hydrogenation of carbon monoxide all require high temperatures (usually >200 "C) and high pressures of C O / H 2 (100-2500 atm) in order to obtain reasonable conversion rates.' One approach to carrying out reduction a t lower temperatures and pressures is to employ a t least two transition metals, preferably one from the early part of the series and one from later in the series, in order to lower the barrier encountered in what is generally considered to be the first step of homogeneous C O reduction, formation of a formyl ligand. The validity of this approach has been strengthened by many examples of reactions between late- and early-transitionmetal complexes that lead to activated carbon monoxide ligands or stable intermediates that one might expect to find in a C O hydrogenation process.2 W e have previously reported the syntheses of heterobimetallic complexes of a I-(tetraethylcyclopentadienyl)-2-(tetramethylcyclopentadieny1)ethane ligand.3 Tethering two different metals to each other via a relatively short flexible linkage might encourage reactions that do not take place in systems containing analogous "unlinked" cyclopentadienyl complexes. Peralkylated cyclopentadienyl ligands bind strongly to most transition metals, and complexes containing such ligands therefore should be able to withstand conditions that may be necessary for C O reduction. Homobimetallic complexes of ligands having two tetramethylcyclopentadienyl rings linked by a one-atom bridge4 or a three-atom bridgeS are known, but preparing a ligand having two tetramethylcyclopentadienyl rings connected by a -CH2CH2bridge has been challenging. The free ligand has now been prepared in low yield, and a monometallic zirconium complex
containing it was prepared.6 Since the relatively new tungstacyclobutadiene complex W(C3Me3)C13(1)' reacts with internal acetylenes to yield tungsten cyclopentadienyl complexes, it should be possible to prepare bimetallic complexes of the $,$Me4CSCH2CH2CSMe4 ligand by methods analogous to those used to prepare complexes containing the ethyl-substituted linked cyclopentadienyl ligand; the permethylated ligand system should allow N M R studies to be simpler and more straightforward. In this paper, we extend and develop the chemistry of heterobimetallic complexes, and some homobimetallic (tungsten/tungsten) complexes, containing the simpler fully methyl-substituted system, qS,$-Me4CSCH2CH2CSMe4 (abbreviated as Cp2).
Results Syntheses of Tungsten/Rhodium Complexes. The (3-pentyny1)cyclopentadienyl complex R h ( q s - M e 4 C S C H 2 C H 2 C = C M e ) ( C 0 ) 2 (2) was prepared by the route reported for the analogous complex Rh($-Me4CSCH2CH2C=CEt)(C0)2.3 The rhodium dicarbonyl center in 2 is apparently incompatible with W(C3R3)CI3complexes3 so it had to be converted into a Rh(II1) dichloride by exposing a pentane solution of 2 to 1 equiv of chlorine (3) was genergas at 0 OC; Rh($-Me4C5CH2CH2C=CMe)Cl2 ated in high yield as an orange powder. Precipitation of 3 immediately from the pentane solution as it formed protected the acetylenic unit from any reaction with chlorine. A I3C N M R spectrum of 3 exhibits signals for the inequivalent acetylenic carbon atoms a t 11.3 and 77.4 ppm. As shown in eq 1, treating 1 with 1.5 equiv of 3 generates two tungsten/rhodium complexes, insoluble [WC14J(Cp2)[RhC12J(Cp2 = $,qs-Me4CSCH2CH2CSMe4)and soluble [ WC12(q2-MeC=
325-416. (2) (a) Hamilton, D.M., Jr.; Willis, W. S.; Stucky, G. D. J . Am. Chem. SOC.1981,103, 4255. (b) Huffman, J. C.; Marsella, J. A,; Caulton, K. G.; Longato, B.: Norton, J. R. J . Am. Chem. SOC.1982,104,6360. (c) Pasynkii, A. A.: Skripkin, Y. V.;Eremenko, I. L.; Kalinnikov, V. T.; Aleksandrov, G. G.; Andrianov, V. G.; Struchkov; Y . T. J . Organomet. Chem. 1979, 165, 49. (d) Barger, P. T.; Bercaw, J. E. Organometallics 1984,3, 278. (e) Wolczanski, P. T.; Threlkel, R. S.; Bercaw, J. E. J . Am. Chem. SOC.1979,101, 220. (f) Threlkel, R.S.; Bercaw, J. E. J . Am. Chem. SOC.1981,103, 2650. (3) Buzinkai, J. F.;Schrock, R. R. Organometallics 1987,6 , 1447. (4) Scholz, H. J.; Werner, H. J . Orgunomet. Chem. 1986,303, C8. (5) (a) Mintz, E. A.; Bensley, D. M., Jr.; Pando, J. C.; Mackey, B. A. Results presented at the Third Chemical Congress of North America, June 1988. Abstract in ACS Diuision of Inorganic Chemistry Winter Newsletter, Jan 1988,No 384. (b) Mintz, E.A.; Pando, J. C.; Zervos, I. J . Org. Chem. 1987,52, 2948.
+
2
( I ) Dombek, B. D. Homogeneous Catalytic Hydrogenation of Carbon Monoxide: Ethylene Glycol and Ethanol from Synthesis Gas. In Aduances in Catalysis; Academic Press: New York, 1983;Vol. 32, pp
3 - - E RhCI,
1
3
1
1 (1)
WCI,
RhCI,
(6) Wochner, F.:Zsolnai, L.; Huttner, G.;Brintzinger, H. H. J . Orgunomet. Chem. 1985,288, 69. (7) Latham, I. A,; Sita, L. R.; Schrock, R. R. Organometallics 1986,5, 1508.
0020-1669/89/1328-2837$01.50/00 1989 American Chemical Society
2838 Inorganic Chemistry, Vol~28, No. 14, 1989
Buzinkai a n d Schrock
7 + ? ( Me8) W
H, Ah ( PMe,) H,
W PMe3
in C6D6
-CH2CH2-
3'0 2 0 ' 0 0 0 -1 0 Figure 1. IH N M R spectrum of [W(PMe3)H5](Cp2)[Rh(PMe,)H2] (5).
CCH2CH2-~5-C5Me4)RhC12]] (Cp2)[RhC12], as a result of formal disproportionation of W(IV) to W(II1) and W(V). The exact nature of the disproportionation reaction has never been elucidated.8 W h a t is presumed to be the soluble tungsten acetylene adduct was not characterized but converted into [WC14](Cp2)[RhCI2] by adding PC15 to the crude reaction mixture. [WC14](Cp2)[RhC12]thereby could be obtained in about 70%yield relative to 1, but the 0.5 equiv of 3 could not be recovered, and the final yield in terms of rhodium therefore was 95% pure as shown by 'H NMR. Recrystallization from a mixture of dichloromethane and ether afforded tan microcrystals that contained 1 .O equiv dichloromethane of crystallization which is not removed in vacuo, as shown by 'H NMR. 'H NMR (CD,CI,): 6 3.4 (v br, 3, axial Me of WMe4), 2.60 and 2.27 (m, 2 each, CH,CH,), 2.09, 2.06, 2.05, and 1.99 (s, 6 each, Me4CSCH2CH2C5Me4),1.65 (br, 9, equatorial methyl groups of WMe4), 0.16 (s, 3, WMe(CO),). I9F NMR (CD,CI,): 6 72.81 (d, J F p= 719, PF,). IR (CH2CI2),cm-I: 2002 s, 1905 s br [u(CO)]. Anal. Calcd for W2C29H4SPC1203F6 (includes 1.0 CH2C12 of crystallization): C, 33.97; H, 4.42; F, 11.12; C1, 6.92. Found: C, 34.26; H, 4.43; F, 11.28; CI, 7.41. [WCI4],(qS,qS-Me4C5CH2CH2C5Me4). [WMe(CO),](qSMe4CSCH2CH2C=CMe) (3.34 g, 7.10 mmol) was dissolved in dichloromethane (40 mL) in a 100-mL Schlenk flask and cooled to -0 OC. W(C3Me3)ClJ7(1.76 g, 4.74 mmol) was added with stirring, and the mixture was allowed to warm to room temperature. An orange precipitate formed, and after 60 min, the mixture was cooled to -0 OC. PCI, (6.0 g, 28.8 mmol) was added with stirring, and the suspension was allowed to warm to room temperature. The mixture was refluxed for 46 h under the pressure of a mercury bubbler (860 Torr). The dark suspension was allowed to cool, and the precipitate was collected by filtration. The solids were washed well with dichloromethane (5 X 12 mL) and dried in vacuo to an orange-brown powder. This powder was combined with PC15 (2.03 g, 9.7 mmol) in chloroform (40 mL) and refluxed with stirring for 40 h. The suspension was allowed to cool, and solids were collected by filtration. [The finely divided powder caused filtration to be very slow.) The solids were transferred to a flask and stirred with dichloromethane (25 mL) for 5 min. The orange solids were isolated by filtration, washed with dichloromethane (2 X mL) and dried in vacuo to an orange powder (3.38 g, 78%). The product is insoluble in organic solvents, as it most likely has an oligomeric or polymeric structure due to intermolecular bridging chlorides. Chlorination was considered to be complete as an IR spectrum exhibited no v(C0) signals. The product could also be obtained from similar reaction of PCls with the dichloromethane reaction solution of [WMe(CO),] (qs-Me4C5CH2CH2C=-CMe) and CI3W(C3Me,), after separating the precipitate of [WC14](Cp2)[WMe(CO),]. IR (Nujol), cm-': 1070 w, 1016 s [v(C5 ring)]. [WMe4]2(q5,q5-Me4CsCH2CH2CSMe4). A 2.8 M solution of MeMgCI (2.1 mL, 5.88 mmol) was diluted to 8 mL with T H F and cooled to -0 OC. [WC1412(q5,qS-Me4CSCH2CH2CSMe4) (0.48 g, 0.8 1 mmol) was added with stirring, and a dark yellow suspension developed upon warming to room temperature. After 3 h, the yellow precipitate was collected by filtration, washed with a THF/ether mixture ( l : l , 2 X 4 mL), and dried in vacuo. Extraction with dichloromethane (-30 mL) [ WC14(PMe3)](q5,q5-Me4C5CH2CH2C5Me4)[WMe(CO)3]. and recrystallization from this solution at -30 OC afforded analytically [WC14](qs,qs-Me4CSCH2CH2CSMe4)[WMe(C0)3] (10 mg, 0.01 1 mmol) pure orange microcrystals (0.20 g from two crops, 48%): 'H NMR was added to a stirred solution of PMe, (5 pL, 0.049 mmol) in di(CD2CI2,wlj2 values in parentheses): 6 44 (1 170 Hz) and 36 (980 Hz) chloromethane (1 mL). A pale green solution immediately formed, and (v v br, CsMe4), 18.5 (510 Hz) (v v br, CH,CH,). EPR (CD2CI,, 25 after 5 min the volatiles were removed to leave a green solid. 'H NMR "C): g = 2.01; wl12 = 210 (similar to the EPR data of WCp*Me4l0). (CD2C1,): 6 2.00 (s) and 1.98 (br sh) ([WMe(CO),](qS-RCsMe4),most Anal. Calcd for W2C28H52:C, 44.46; H, 6.93. Found: C, 44.04; H, likely C5MeP2and CsMea2, respectively), 0.02 (s, WMe), -3.4 (v br, 6.90. [WCI4(PMe3)](qS-RCSMe4)), -7.6 (v br, PMe,). EPR (CD2C12,25 "C): g = 1.89; wi12 = 44 G (virtually identical with the EPR data for Acknowledgment. This work was supported by the Director, WCp*CI4(PMe3)'O in CH2CI2: g = 1.89; w l l 2 = 52 G). IR (CH,CI,), Office of Basic Energy Research, Office of Basic Energy Sciences, cm-I: 2002 s, 1905 s br [u(CO)]. Chemical Sciences Division of the U S . Department of Energy, [WMe4](qS,qS-Me4C5CH2CH2CsMe4)[WMe(CO)3] (18). A 2.8 M under Contract DE-FG02-86ER13564. J.F.B. thanks the N a solution of MeMgCl (0.85 mL, 2.38 mmol) was diluted to 6 mL with tional Science Foundation for a predoctoral fellowship. T H F and cooled to -30 "C. [WCl4](qs,qs-Me4CsCH2CH2CSMe4)[WMe(CO),] (400 mg, 0.456 mmol) was added as a solid with stirring. Registry No. 1, 102342-00-7; 2, 120905-76-2; 3, 120905-77-3; 4, The suspension became green-yellow and then yellow as it was allowed 120905-78-4; 5, 120905-79-5; 6, 120905-80-8; 7, 120905-81-9; 8, 120905-83-1; 9, 120905-84-2; 10, 120905-85-3; 11, 120906-13-0; 12 to warm to room temperature. After 70 min, the yellow precipitate was isolated by filtration, washed with a THF/ether mixture (l:l, 2 X 3 mL), (isomer l ) , 120905-86-4; 12 (isomer 2), 120905-87-5; 12 (isomer 3), 120905-88-6; (12)(PF6) (isomer l ) , 120905-90-0; (12)(PF6) (isomer 3), and dried in vacuo. This solid was extracted with dichloromethane (40 mL), and yellow needles were obtained by standing the extract at -30 120905-94-4; 13 (isomer l), 120905-95-5; 13 (isomer 2), 120905-96-6; OC (I51 mg from two crops, 41%). 'H NMR (CD2CI2;see Figure 3): 13 (isomer 3), 120905-97-7; 14, 120905-98-8; 15, 120905-99-9; 16, d 36 (v v br, WCSMe4), 17 (v v br, [WMe4]C5CH2CH2),4.0 (v br, 120906-1 1-8; 17, 120906-00-5; 18, 120906-01-6; 19, 120906-03-8; [WMe4]C5CH2CH2), 2.21 (br, [WMe(CO)JC,Me",), 2.08 (s, [WMeHC5Me4(CH2CH2C=CMe) (isomer 1 ), 120905-72-8; HC5Me4(CO),]CsMeS2), 0.22 (s, WMe(CO),). IR (CH2CI2),cm-I: 2003 s, 1903 (CH,CH,C=CMe) (isomer 2), 120905-74-0; HCsMe4(CH2CH2C= s br [u(CO)]. EPR (CH,Cl,, 25 "C): g = 2.01; wl12 = 135 G (virtually CMe) (isomer 3), 120905-75-1; LiCsMe4(CH2CH2C=CMe), 120905identical with the EPR data for WCp*Me4Io). Anal. Calcd for 73-9; [Rh(C0)2CI],, 14523-22-9; [WC14](qs,q5-
Inorg. Chem. 1989, 28, 2846-2853
2846
Me4CSCH2CH2CSMe4)[RhC12],120906-04-9; PMe,, 594-09-2; [WHs(PMedl (?',?'-Me4CSCH2CH2CsMeq)r [RhMe(CO)(PMe,)l [03SCF311, 120906-06-1; [FeCp2][PF6], 11077-24-0; Co2(CO),, 10210-68-1; WCp*Me(CO)3, 34807-90-4; W(CO)6, 14040-11-0; [WMe(CO),]($-
Me4CsCH2CH2C=CMe), 120906-07-2; [WC14(PMe3)](qS,aSMe4C5CH2CH2CSMe4)[WMe(C0),], 120906-08-3; [WC14]2($,~sM e 4 C S C H 2 C H 2 C S M e 4 ) , 120906-09-4; [WMe4l2($,qSMe4CsCH2CH2CsMe,),120906-10-7.
Contribution from the Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
Electronic Structure of Piano-Stool Dimers. 8. Electronically Induced Conformational Changes in High-Valent Bimetallic Chalcogen Complexes of the Type [CpML],(p-L), (M = Mo, Re; L = S, 0)' Bruce E. Bursten**2and Roger H. Cayton Receioed February 17, I988 Fenske-Hall molecular orbital calculations have been applied to a series of bimetallic chalcogen complexes that adhere to the general formula Cp2M2L4,where M = Mo, Re and L = 0, S. In the case of M = Mo and L = S three geometric isomers were considered: [CpMoSI2(p-S)2(l), [CpMo]2(p-S)2(p-S2) (2), and [CpMoSI2(pS2)(3). Series of calculations were performed in order to create a potential surface modeling an isomerization pathway among the three isomers. It was found that the conversion from 1 to 2 is a photochemically allowed process, whereas the conversion from 2 to 3 is allowed thermally. In the related oxo compound [CpMo0]2(p-O)2 (4), the reason for the puckering of the central Mo202core was found to be due to a more favorable Mo-(p-0) a interaction in the slightly folded geometry. In addition, folding the p-oxo ligands of 4 toward the cis Cp rings, rather than away from the Cp rings in a sterically less congested environment, was found to be the electronically preferred geometry. Further puckering of the p o x 0 ligands of 4 to form a p-peroxo structure was calculated to be a significantly higher energy process than the same distortion coordinate associated with the sulfide analogue. Calculations on the d 2 d 2complex [CpReOI2(p-O), (5) at Re-Re distances varying from 2.74 to 3.54 A indicate the most stable configuration to be at 3.14 A. This stable geometry at 3.14 A appears to be the result of the generation of two nonbonding, Re-based orbitals that are then able to hold the four metal-based electrons. At both longer and shorter R e R e distances, the p-oxo ligands destabilize one of the two nonbonding orbitals to generate a high-energy HOMO. Discrete bimetallic organotransition-metal chalcogen complexes have recently been the subject of extensive research. Compounds of this type represent a link between ionic, solid-state metal chalcogenides and low-valent organometallic systems. Of particular interest are sulfur-containing species of this type that serve as models for heterogeneous desulfurization catalysts used in the purification of petroleum product^.^*^ A n interesting series of bimetallic chalcogen complexes is that which adheres to the general formula ($-C5RJ2M2L4, where L = 0, S. Crystallographically characterized members of this high-valent piano-stool dimer series have been prepared for a variety of transition metals including V,5 Cr,6 Mo,'-'' Re,I2 Fe,I3*l4and Co.l4 N o t surprisingly, the structures of these compounds a r e highly dependent upon the oxidation state and corresponding electronic requirements of the metal. Moreover, even within the series of M o complexes where L = S, three different structure types have been observed, viz. [ C P * M O S I Z ( C L - S )(11, ~ [ C P * M O I Z ( K - S M C L - S(21, ~) and [Cp*MoSl2(p-S2)(3) (Cp* = $-C5Me5), two of which (1,2) have ( I ) Part 7: Bursten, B. E.; Cayton, R. H. Polyhedron 1988, 7, 943-954. (2) (3) (4) (5)
Camille and Henry Dreyfus Foundation Teacher-Scholar (1984-1989). Massoth, F. E. Ado. Caral. 1978, 27, 265 and references therein. Schuman, S. C.; Shalit, H. Caral. Reu. 1970, 4, 245. Bolinger. C. M.; Rauchfuss, T. B.; Rheingold, A. L. J . Am. Chem. Soc.
1983, 105. 6321-6323. (6) Heberhold, M.; Kremnitz, W.; Razavi, A,; Schollhorn, H.; Thewalt, U . Angew. Chem. 1985. 97, 603-604; Angew. Chem., Int. Ed. Engl. 1985, 24,601-602. (7) Couldwell, C.; Prout, K . Acta Crystallogr. 1978, 834, 933-934. (8) Arzoumanian, H.; Baldy, A,; Pierrot, M.; Petrignani, J.-F. J . Organomer. Chem. 1985. 294, 327-331. (9) Stevenson, D. L.; Dahl, L. F. J . Am. Chem. Soc. 1967,89, 3721-3126. (IO) Brunner. H.; Meier, W.; Wachter, J.; Guggolz, E.; Zahn, T.; Ziegler, M . L. Organometallics 1982, I , 1107-1 113. ( I I ) DuBois. M . R.; DuBois, D. L.; VanDerveer. M. C.; Haltiwanger, R. C. Inorg. Chem. 1981, 20, 3064-3071. (12) Herrmann, W. A. Personal communication. ( 1 3) Weberg, R.; Haltiwanger. R. C.; DuBois, M. R . Organometallics 1985. 4 , 1315-1318.
(14) Brunner. H.; Janietz, N.; Meier, W.; Sergeson, G.; Wachter, J.; Zahn, T.; Ziegler. M . L . Angew. Chem.. Inr. Ed. Engl. 1985. 24. 1060-1061
0020-1 669/89/ 1328-2846$01.50/0
been characterized crystallographically.loJ'These three isomers are illustrated in A. The chemistry of these species is also relevant
1
2
3
A
t o the understanding of the coordination of sulfur ligands t o molybdenum in biological system^.'^,'^ T h e tetraoxo analogues of this system a r e also known for the metals Cr, Mo, and Re, and in each case their structures resemble the basic structure of 1. T o date, there has been no evidence for peroxo analogues of structure types 2 and 3 in the piano-stool dimer class. Because this series of compounds displays such a plethora of structure types and alternating metal d counts, a n d because of its close relationship to important heterogeneous and homogeneous systems, the need for a thorough understanding of the electronic structure and bonding operating within this system is obvious. W e have found previously, in calculational treatments of piano-stool dimers containing x-acid ligands, that the Fenske-Hall method provides reliable results for such complexes and can be used t o explain certain anomalous reactivity patterns a s well a s conformational preferences in these low-valent system^.^^'^^'^ In this contribution we have extended this approach t o include the high-valent bimetallic series CpzM2L4,where M = Mo, L = S, 0 and M = Re, L = 0. These results will be used to examine ( I 5) Coughlan, M. P., Ed. Molybdenum and Molybdenum-Containing Enzymes; Pergamon Press: New York, 1980. ( 16) Newton, W. C., Otsuka, S., Eds. Molybdenum Chemistry of Biological Significance; Plenum Press: New York, 1980. (17) Bursten. B. E.; Cayton, R. H . Organometallics 1988, 7, 1342-1348. ( 1 8 ) (a) Bursten, B. E.; Cayton, R. H . J . Am. Chem. SOC.1987, 109, 6053-6059. (b) Bursten, B. E.; Cayton, R. H. J . Am. Chem. Soc. 1986, 108. 8241-8249 and references therein.
9 1989 American Chemical Society
