3928
J . Am. Chem. SOC.1987, 109, 3928-3936
cant of only 19.l0, while this angle for its cobalt complex26is 44O, a considerably greater difference than that between the unprotonated free base and its complex. Metalloporphyrins other than heme are able to bind to heme oxygenase, and zinc complexes act as competitive inhibitors of this enzyme. When De Matteis and co-workers tested the inhibitory ability of a series of zinc N-alkylporphyrin complexes, larger N-substituents (ethyl and propyl) were found to be less inhibitory than N-methylp~rphyrins.~They proposed that the correlation between structure and inhibition for this enzyme was also related to the cant of the N-substituted pyrrole ring, with larger groups causing a greater tilt. While there are, indeed, substantial differences in the cant of the N-substituted pyrrole ring among the members of the series of N-substituted zinc(I1) porphyrins reported herein, these differences are not straightforwardly related to the “bulk” of the N-substituent. In fact, the pyrrole ring for which the N-substituent is a benzyl group is less canted (by 7O) than in the complex with a methyl substituent. In the series of N-alkylporphyrins studied by DeMatteis, the N-substituents are very similar (N-methyl-, N-ethyl-, and N-npropyl groups), all involving an N-methylene linkage. No substantial difference in the cant of the pyrrole ring is expected for these compounds. On the basis of our results, the differences in heme oxygenase inhibition for the zinc( 11) complexes of N-alkylprotoporphyrin are due not to the cant of the N-substituted pyrrole ring but instead to the requirement for additional space (26) Goldberg, D. E.; Thomas, K. M. J . Am. Chem. Soc. 1976, 98, 913.
in the binding pocket to accommodate more bulky N-substituents. The need to accommodate the N-substituent also explains the marked difference in inhibition of ferrochelatase by N-npropylprotoporphyrin IX and N-n-propylmesoporphyrin IX in comparison with the corresponding N-methyl and N-ethyl free base porphyrins.
Acknowledgment. The Nicolet R3m/E diffractometer and crystallographic computing system at Colorado State University were purchased with funds provided by the National Science Foundation (CHE 81-03011). Work at Hunter College was generously supported by the National Cancer Institute of the NIH (CA 25427) and the PSC-CUNY grants program to D.K.L. and by a NATO grant to D.K.L. and D.M. (583-83). Work at Colorado State University was supported by the National Institute of General Medical Sciences of the N I H (GM 30306) and the Biomedical Research Support Grant program of the NIH. Supplementary Material Available: Table S- 1, anisotropic thermal parameters for [Zn(N-Bz-TPP)Cl],Table S-11, calculated hydrogen atom coordinates for [Zn(N-Bz-TPP)CI], Table S-111, least-squares planes for [Zn(N-Bz-TPP)Cl], Table S-V, anisotropic thermal parameters for [Zn(N-Ph-TPP)Cl], Table S-VI, calculated hydrogen atom coordinates for [Zn(N-Ph-TPP)Cl], and Table S-VII, least-squares planes for [Zn(N-Ph-TPP)Cl] (1 4 pages); Table S-IV, observed and calculated structure factors for [Zn(N-Bz-TPP)Cl], and Table S-VIII, observed and calculated structure factors for [Zn(N-Ph-TPP)Cl] (57 pages). Ordering information is given on any current masthead page.
Structural Diversity in Bis(pentamethylcyclopentadieny1)lanthanide Halide Complexes: X-ray Crystal Structures of [ (C5Me5)2SmC1]3and
(C5Me5)loSm5C15[Me(OCH2CH2)40Me] William J. Evans,*lP.bDonald K. Drummond,l* Jay W. Grate,la Hongming Zhang,Ib and Jerry L. Atwood*lb Contribution from the Departments of Chemistry, University of California. Irvine, Irvine, California 9271 7, and University of Alabama, University, Alabama 35486. Received November 19, 1986
Abstract: (CSMe5)2SmCI(THF) can be desolvated at 150 “C to form a material which crystallizes from hexane/toluene as the cyclic trimer [(C5Mes)2Sm(p-Cl)]3in space group C2/c with a = 21.665 (10) A, b = 14.203 (8) A, c = 20.234 ( 8 ) A, p = 108.63 (6)’, V = 5900 A’, and DaId = 1.54 g cm-, for 2 = 4 (four trimetallic units per unit cell). The three bridging chloride ions connect the three (CSMeS),Smunits via 2.849 (7)-2.892 (7) A Sm-(p-CI) distances in a planar six-membered Sm,(p-CI), ring. In the presence of tetraglyme, crystals of ((C5Me5)2C1Sm(p-C1)Sm(C5Me5)2[p,~4-CH3(OCH2CH2),0CH3]Sm(CSMe,),)+l[(CsMes)2ClSm]2(p-Cl))-form in space group P 2 , / a with a = 19.185 (8) A, b = 26.627 (9) A, c = 24.760 (9) A, /3 = 115.16 (5)’, V = 11 448.3 A3, and Dcalcd= 1.45 g cm-, for Z = 4 (four pentametallic units per unit cell). The structure contains four independent types of (C5Mes)2Smunits and a variety of Sm-CI bonds. This allows a detailed analysis of trends in structural preferences, bond distances, and angles.
Recent studies of the chemistry of organolanthanide alkyl and hydride complexes have shown that reactivity can be highly dependent on the structure of the Hence, the degree (1) (a) University of California, Irvine. (b) Alfred P. Sloan Research Fellow. (c) University of Alabama. (2) Evans, W. J. Ado. Organomet. Chem. 1985, 24, 131-177. (3) Schumann, H. Angew. Chem., Int. Ed. Engl. 1984, 23, 474-493. (4) Watson, P. L.; Parshall, G. W. Acc. Chem. Res. 1985, 18, 51-56 and references therein.
0002-7863/87/1509-3928$01.50/0
of steric saturation around the metal, the presence of terminal vs. bridging ligands, and the degree of oligomerization of the complex can strongly influence how a Ln-CR, or Ln-H unit reacts (Ln = lanthanide metal).2 As a consequence, defining the (5) Evans, W. J.; Dominguez, R.; Hanusa, T. P. Organometallics 1986, 5, 263-270. (6) Wayda, A. L.; Rogers, R. D. Organometallics 1985, 4 , 1440-1444. (7) Jeske, G.; Lauke, H.; Mauermann, H.; Schumann, H.; Marks, T. J. J . A m . Chem. SOC.1985, 107, 81 11-81 18 and references therein.
0 1987 American Chemical Society
J. Am. Chem.SOC.,Vol. 109, No. 13, 1987 3929
Bis(pentamethylcyclopentadieny1)lanthanideHalides
Table 1. Crystallographically Defined Bis(cyclopentadieny1) Derivatives of Trivalent Lanthanides alkyl or hydride analogues characterized by X-ray crystallography halide derivatives characterized by X-ray crystallograuhy
Heterometallic Bridged Species
(CsMeS)zYb(p-X)2Li(EtzO)z21 (X = CI, I) (CSMes)zPr(p-Cl)2Na( DME)22
(C,HS)zLn(p-Me)2Li(TMEDA)zs (Ln = Lu, Er) (CSH5)2Yb(pMe)zA1Me226
(C,H4SiPh2Me)zYb(p-Cl)zLi(Et20)221 [C,H3(SiMe3)z]2Nd(p-C1)2Li(THF)223 (C5Me5)2Yb(p-CI)zAIC1221 [ Me2Si(C5Me4)2Nd]z(p-Cl)3Li(THF)24 (CSH5)2LnCI(THF)27 (C5Me,)2LnX(THF)28 (Ln = Sm, X = I, CI) (Ln = Y, X = CI)
I [CSH3(SiMe3)z]2NdC12){AsPh4)29
structural trends of organolanthanide complexes is crucial to understanding the chemistry of these compounds. X-ray crystallography provides solid-state information on general structural patterns, but unfortunately the isolation of X-ray quality crystals of the often highly reactive alkyl and hydride complexes can be difficult. Even when good crystals are available, location of a hydride ligand in the presence of a heavy metal may be d i f f i c ~ l t , and * ~ ~ambiguities in alkyl bonding can arise. For example, bridging methyl groups can bond via metal-carbon or via metal-hydrogen interactions.l0>” Historically, lanthanide halide analogues of organolanthanide hydride and alkyl complexes have proven useful in defining structural trends.l2-I4 The generally less reactive halide analogues are not as difficult to isolate in high quality crystalline form, and the location of the halide ligand can be specified more precisely. For trivalent bis(cyclopentadieny1)lanthanide complexes [(CSRS)2LnZ],(R = H, Me; Z = halide, hydride, alkyl; n = 1-3), more structural information is available for the halide derivatives than for the hydride or alkyl complexes as shown in Table I.1s-3s (8) Evans, W. J.; Meadows, J. H.; Wayda, A. L.; Hunter, W. E.; Atwood, J. L. J . A m . Chem. SOC.1982, 104, 2008-2014. (9) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J . A m . Chem. SOC.1983, 105, 1401-1403. (10) Holton, J.; Lappert, M. F.; Ballard, D. G. H.; Pearce, R.; Atwood, J. L.; Hunter, W. E. J . Chem. SOC.,Dalton Trans. 1979, 54-61. (1 1) Tilley, T. D.; Andersen, R. A,; Zalkin, A. J . A m . Chem. SOC.1982, 104, 3725-3727. Tilley, T. D.;Andersen, R. A,; Zalkin, A. Inorg. Chem. 1984, 23, 2271-2276. (12) Lappert, M. F.;Singh, A. J. Orgunornet, Chem. 1982, 239, 133-141. (13) Raymond, K.N.; Eigenbrot, C. W., Jr. Acc. Chem. Res. 1980, 13, 276-28 3. (14) Evans, W. J.; Peterson, T. T.; Rausch, M. D.; Hunter, W. E.; Zhang, H.; Atwood, J. L. Organometallics 1985, 4 , 554-559. (15) Atwood, J. L.; Smith, K. D. J . Chem. SOC.,Dalton Trans. 1973, 2487-2490. (16) Baker, E. C.; Brown, L.D.; Raymond, K. N. Inorg. Chem. 1975, 14, 1376-1379. (17) Lappert, M. F.;Singh, A,; Atwood, J. L.; Hunter, W. E. J . Chem. SOC.,Chem. Comrnun. 1981, 1190-1 191. (18) Hock, N.;Oroschin, W.; Paolucci, G.; Fischer, R. D. Angew. Chem., Int. E d . Engl. 1986, 25, 738-739. (19) Evans, W. J.; Drummond, D. K.; Hanusa, T. P. Doedens, R. J., submitted for publication in Organometallics.
Q Figure 1. (A) Bent metallocene view of a (C5R5)2M(p-H)zM(C,Rs)z molecule. (B) Structure observed in [(C,Me,),Srn(~-H)],.
Since our discovery and X-ray crystal study of the bis(cyc1opentadieny1)samarium hydride, [(C,Me,)2Sm(p-H)]2,9we have (20) Jin, Z.; Liu, Y.; Chen, W., personal communication. (21) Watson, P. L.; Whitney, J. F.; Harlow, R. L. Inorg. Chem. 1981, 20, 3271-3278. (22)Albrecht, I.; Hahn, E.; Pickardt, J.; Schumann, H , Inorg. Chim. Acta 1985, 110, 145-147. (23) Lappert, M. F.; Singh, A,; Atwood, J. L.; Hunter, W. E. J Chem. SOC.,Chem. Commun. 1981, 1191-1193. (24)Jeske, G.; Schock. K. E.: Swemton. P. N.. Schumann. H.; Marks, T. J. i.Am. Chem. SOC.1985, 107, 8103-8110. (25) Schumann, H.; Reier, F.-W.; Hahn, E. Z . Narurforsch. 1985, 406, 1289-1 292. (26) Holton, J.; Lappert, M. F.; Ballard, D. G. H.; Pearce, R.; Atwood, J. L.; Hunter, W. E. J . Chem. SOC.,Dalton Trans. 1979,45-53. (27) Ni, C.; Zhang, Z.; Deng, D.; Quian, C. J . Organomet. Chem. 1986, 306, 209-2 14. (28) Evans, W.J.; Grate, J. W.; Levan, K. R.; Bloom, 1.; Peterson, T. T.; Doedens, R. J.; Zhang, H.; Atwood, J. L. Inorg. Chem. 1986, 25, 3614-3619. (29) Lappert, M. F.;Singh, A.; Atwood, J . L.; Hunter, W . E.; Zhang, H.-M. J . Chem. SOC.,Chem. Commun. 1983, 69-70. (30! Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. Organomerallics 1985, 4 , 112-1 19. (31) Evans, W. J.; Wayda, A. L.; Hunter, W. E.; Atwood, J. L. J . Chem. SOC.,Chem. Commun. 1981, 292-293. (32) Schumann, H.; Genthe, W.; Bruncks, N.; Pickardt, J. Organometallics 1982, I , 1194-1200. (33) Evans, W. J.; Dominguez, R.; Levan, K. R.; Doedens, R. J. Orgunometallics 1985, 4 , 1836-1841. (34) Jeske, G.; Lauke, H.; Mauermann, H.; Swepston, P. N.; Schumann, H.; Marks, T. J. J . A m . Chem. SOC.1985, 107, 8091-8103.
3930 J . A m . Chem. SOC.,Vol. 109, No. 13, 1987 been interested in examining the formally analogous halide complex Y[(C5Me5)2Sm(p-C1)]2".The hydride complex had an unusual structure which was not that predicted for a normal transition-metal bent m e t a l l ~ c e n eand ~ ~ which did not match the lowest energy structure predicted by a molecular orbital analysis of [ (C5H5)2SmH]2.37 A typical bent metallocene dimer would contain a planar Sm,(p-H), unit which would bisect the (ring centroid)-metal-(ring centroid) angle of each (C5MeS)*Smgroup. In this case, as shown in Figure IA, the four CsMes ring centroids would describe a square-planar geometry. In the observed structure, Figure IB, the four CsMeS ring centroids define a tetrahedron, Le., one (C5Me5)2Smunit has twisted 90° with respect to the other. In this geometry, it is impossible for a Sm,(p-H), plane to simultaneously bisect the (ring centroid)-metal-(ring centroid) angles of each (CSMeS),Sm unit. Unfortunately, in the hydride structure, the hydrogen atoms could not be 10cated.~ By studying the (C5MeS),SmCI system we sought to determine if the chloride analogue (a) would be structurally similar to the hydride, (b) would adopt the bent metallocene structure due to the larger size of the chloride ligands vs. the hydrides, or (c) would adopt a different geometry. In this report, we describe the synthesis and crystallographic characterization of two bis(pentamethylcyclopentadieny1)samarium chloride systems which follow option c above. These complexes define new structural classes of bis(cyc1opentadienyl)lanthanide halides and show that seueral different types of coordination geometry are available to a single set of ligands in a crystalline organolanthanide complex. Experimental Section The complexes described below are extremely air- and moisture-sensitive. Therefore, both the syntheses and subsequent manipulations of these compounds were conducted under nitrogen with rigorous exclusion of air and water using Schlenk, vacuum line, and glovebox (Vacuum/ Atmospheres HE-553 Dri Lab) techniques. Materials. Hexane was washed with sulfuric acid, dried over MgSO,, and distilled from potassium benzophenone ketyl solubilized with tetraglyme. Toluene and T H F were distilled from potassium benzophenone ketyl. Benzene-d6 and toluene-dg were vacuum transferred from potassium benzophenone ketyl. (C5Me,)2SmCI(THF) was prepared by reacting t-C,H,CI with (CSMe5)2Sm(THF)2as previously described.28 [(C5Me5)2Sm(fi-Cl)]3(1). In a glovebox, (C5Me5)2SmCI(THF)(0.85 g, 1.6 mmol) was placed in a tube fitted with a high vacuum stopcock adapter. The tube was attached to a vacuum line, and the sample was heated for 36 h at 90 "C under dynamic vacuum at about torr. The originally orange sample turned orange-red during this time. The tube was removed from the vacuum line and taken into a glovebox containing no ether solvents. The sample was removed from the tube (0.61 g, 83%) and found to be pure by 'H N M R spectroscopy, which showed a single C5Me5resonance. Anal. Calcd for Sm3C60H90C13:Sm, 33.0. Found: Sm, 32.1; 'H N M R (C6D6) 6 -0.22 ( s , C5Me5). The 'H N M R shift is highly sensitive to traces of THF. Opening an N M R tube containing the sample for 1 min in a glovebox containing some T H F vapor can cause a downfield shift of as much as 0.04 ppm. N M R samples which retained the red color of unsolvated 1 (vs. the orange color of (C5Me5),SmCI(THF)28)have exhibited the C5MeSresonance at shifts as positive as 6 0.23 (cf. 6 1.20 for fully solvated (C5Me5)2SmC1(THF)2g):IR (KBr) 2850 w, 2400 w, 1440 m br, 1250 w, 1130 w, 1010 m br, 790 m cm-I. X-ray quality crystals of [(C5Me5)2Sm(w-CI)]3were grown at room temperature by layering hexane onto a saturated toluene solution made by dissolving the sample in hot toluene. (C5Me5)loSm5CIS[Me(OCH2CH2)40Me] (2). (C5Me5)2SmCI(THF) was desolvated as described above at 150 O C over a 1-h period. During this time the pressure rose from to torr and then dropped back to torr. The remaining pink powder was heated to 175 "C for 30 min, and the tube was sealed. The material was sublimed at 165 "C over a 3-day period to give red needles which were not, however, X-ray quality. (A sample of the crystals in THF-d8 gave a clean ' H N M R spectrum characteristic of (C5Me5)2SmCI(THF).) A sample of the sublimed crystals was stirred in toluene, and the resulting solution was decanted into a vial. Hexane containing a trace of tetraglyme was layered over the toluene, and the vial was loosely capped. After the solvent (35) Evans, W. J.; Meadows, J. H.; Wayda, A. L.; Hunter, W. E.; Atwood, J. L. J . Am. Chem. SOC. 1982, 104, 2015-2017. (36) Lauher, J. W.; Hoffmann, R. J . Am. Chem. SOC.1976, 98, 1729-1 742. (37) Ortiz, J . V.; Hoffmann, R. Inorg. Chem. 1985, 24, 2095-2104.
Evans et al.
compd mol wt space group cell constants a, 8, b, 8, c, 'A a,deg 6, deg 73 deg cell VOI,A molecules/unit cell p(calcd), g cm-3 w (calcd), crn-' radiation max/crystal/dimens, mm scan width, deg stnd reflctns decay of stnds reflctns measured 28 range obsd reflctns no. of parameters varied
GOF R Rw
Sm3C13C60H90
Sm5C15C1
1368.80 c2/c
2503.65 P2,la
21.665 (10) 14.203 (8) 20.234 (8) 90.00 108.63 (6) 90.00 5900.06 4 trimetallic units 1.54 31.69 Mo K a 0.15 X 0.20 X 0.15 0.8 0.2 tan 8 930, 008, 440 f 2% 5315 2-36' 1400 149 1.23 0.053 0.059
19.185 (8) 26.627 (9) 24.760 (9) 90.00 115.16 (5) 90.00 11448.3 4 pentametallic units 1.45 27.24 Mo K a 0.15 X 0.25 X 0.10 0.8 0.2 tan 8 400, 040, 006 f2% 8954 2-36" 5218 626 1.55 0.087 0.089
+
lOHI7Z05
+
evaporated from the vial, crystals of (C5Me5)loSm5C15[Me(OCH2CH2),0Me] remained. X-ray Data Collection, Structure Determination, and Refinement for [(C5Med2Sm(~-C1)I3 (1) and ( C S M ~ ~ ) ~ , S ~ ~ C I ~ [ M ~ ( O C H ~ C H ~ ) ~ (2). Single crystals of the air-sensitive compounds were sealed under N2 in thin-walled glass capillaries. Final lattice parameters as determined from a least-squares refinement of ((sin 8)/X)2 values for 25 reflections (28 > 20") accurately centered on the diffractometer are given in Table 11. Data were collected on an Enraf-Nonius CAD-4 diffractometer by the 8-20 scan technique as previously described.26 Summaries of data collection parameters are given in Table 11. The intensities were corrected for Lorentz, polarization, and absorption effects. For the latter, an empirical method similar to that of Churchill was e m p l ~ y e d . ~ ' Systematic absences indicated that the space group for 1 could be Cc or C2/c. Subsequent solution and refinement of the structure showed C2/c to be the correct choice. The two crystallographically independent The calsamarium atoms were located with the aid of MULTAN culation of difference Fourier maps allowed the location of the remaining non-hydrogen atoms. Neutral atom scattering factors for Sm, C1, and C were taken from Cromer and Waber.40 The full-matrix least-squares refinement (using the SHELX program system4') with isotropic temperature factors for all non-hydrogen atoms led to a reliability index R = CllFol- ~ F J ~ / ~=~0.095. F , , ~Conversion to anisotropic thermal parameters for S m and C1 atoms and further refinement gave R = 0.053 based on 1400 observed reflections ( ( I ) > 341)). The function minimized in the least-squares calculation was X:wlAFl with unit weights. In the last stage of refinement no parameter shifted by more than 0.01 of its estimated standard deviation. A final difference Fourier synthesis showed no unaccounted electron density. No systematic variation of w(lFol- IFJ) vs. lFol or (sin @)/A was noted. The final values of the positional parameters for l are given in Table 111. For complex 2, the space group was uniquely determined to be P2,/a (an alternate setting of P2,/c) from systematic absences. Solution refinement was carried out as described for 1. MULTAN BO was again used to locate the independent samarium positions. With isotropic temperature factors for all non-hydrogen atoms, R = 0.1 14. With anisotropic thermal parameters for the Sm and CI atoms, R = 0.087. Final fractional coordinates for 2 are given in Table IV.
Results Synthesis. Bis(pentamethylcyclopentadieny1)samarium chloride complexes can be made by reacting 2 equiv of MCSMe5(M = (38) Churchill, M. R.; Hollander, F. J. Inorg. Chem. 1978, 17, 1957-1962. (39) MULTAN so, a system of computer programs for the automatic solution of crystal structures from X-ray diffraction data, by P. Main et al., 1980. (40) Cromer, D. T.; Waber, J. T. Acta Crystallogr. 1965, 18, 104-109. (41) SHELx, a system of computer programs for X-ray structure determination, by G. M. Sheldrick, 1976.
Bis(pentamethylcyclopentadieny1)lanthanideHalides Table 111. Final Fractional Coordinates for [(C5Me5),Srn(pCl)ll atom Sm(l)
xla 0.877 13 (6) 1.oooo 0.9175 (3) 1 .oooo 0.765 (1) 0.812 (1) 0.829 ( I ) 0.794 ( I ) 0.754 ( I ) 0.850 ( I ) 0.833 ( 1 ) 0.892 (1) 0.943 ( I ) 0.915 ( I ) 0.940 ( 1 ) 0.892 ( 1 ) 0.910 ( I ) 0.969 ( I ) 0.988 (1) 0.728 ( I ) 0.833 (1) 0.871 ( I ) 0.792 ( 1 ) 0.692 ( I ) 0.804 (1) 0.766 (1) 0.896 ( 1 ) 1.017 (1) 0.954 ( 1 ) 0.936 ( 1 ) 0.826 (1) 0.866 (1) 0.999 (2) 1.050 ( 1 ) \
,
Ylb
ZIC
-0.0416 (1) -0.3856 ( I ) -0.2313 (5) 0.0041 (7) -0.063 (2) -0.042 (2) 0.053 (2) 0.090 (2) 0.015 (2) 0.049 (2) -0.045 (2) -0.099 (2) -0.033 (2) 0.056 (2) -0.386 (2) -0.420 (2) -0.508 (2) -0.534 (2) -0.462 (2) -0.159 (2) -0.108 (2) 0.114 (2) 0.195 (2) 0.027 (2) 0.137 (2) -0.085 (2) -0.203 (2) -0.059 (2) 0.145 (2) -0.297 (2) -0.372 (2) -0.574 (2) -0.631 (3) -0.451 (2)
0.14647 (7) 0.2500 0.1805 (3) 0.2500 0.176 (1) 0.241 (1) 0.238 (1) 0.170 (1) 0.133 ( 1 ) 0.019 (1) 0.001 ( I ) 0.023 (1) 0.056 (1) 0.054 ( I ) 0.349 ( I ) 0.289 (1) 0.272 (1) 0.322 (1) 0.370 ( I ) 0.157 (1) 0.305 (1) 0.298 ( I ) 0.150 (1) 0.066 (1) -0.010 ( I ) -0.045 (2) 0.004 (1 ) 0.084 ( I ) 0.078 ( I ) 0.388 (1) 0.247 ( I ) 0.215 (2) 0.335 (2) 0.436 (1) ~,
\
,
alkali metal) with SmC1, in THF28,42or by oxidizing ( C , M ~ , ) , S I ~ ( T H Fwith ) ~ an alkyl chloride.28 Since the first route forms MCI adducts (C,Me5),Sm(p-C1),ML2 (L2 = (THF),, (Et,O),, or TMEDA) as the predominant product, the second synthesis is preferred. The (C,Me,),SmCI(THF) product obtained must be desolvated to get a complex with the desired empirical formula "(C5Me5)2SmC1". Powdered (C,Me5),SmC1(THF) can be desolvated under high vacuum at temperatures ranging from 90 to 150 OC. The sample becomes orange-red upon desolvation. Sublimation occurs very slowly at 165 OC or more rapidly at 200 "C and can give red crystals. The desolvated material is insoluble in hexane, sparingly soluble in benzene and toluene, and more soluble in boiling toluene. The sublimed material has a single broad (wIl2 = 9.7 Hz) C5MeS resonance at -0.22 ppm in the IH N M R spectrum. The position of the peak is very sensitive to trace amounts of THF. Exposure of an NMR sample in the tube to THF vapor moves the resonance downfield. Addition of a full equivalent of THF-d8 to the N M R sample sharpens and shifts the resonance downfield to 1.2 ppm, which is characteristic of the original solvate.28 Samples of the powdered, desolvated material which have not been sublimed typically have their CsMes resonance at 0.07-0.23, and traces of coordinated T H F are sometimes detected around -0.3 and -1.4 PPm. Although sublimation yielded single crystals, none of those examined diffracted well enough for a structural determination. X-ray quality crystals of [(C,Me,)2Sm(p-C1)]3, 1, were successfully obtained by diffusion of hexane into a saturated toluene solution of desolvated material. Crystals of (C5Me,),,Sm,C1,[Me(OCH,CH,),OMe], 2, were obtained when hexane containing a trace of tetraglyme was layered over a more dilute solution of the sublimed material in toluene. Structure of [(C,Me,)2Sm(p-C1)]3. In the absence of any coordinating ether, (C,Me,),SmCl units crystallize into trimeric molecular species as shown in Figure 2. The Sm,(p-CI), unit (42) Tilley, T. D.; Andersen, R. A. Inorg. Chem. 1981, 20, 3267-3270.
J. Am. Chem.SOC.,Vol. 109,No. 13, 1987 3931 Me23 Me23'
Me25'
Me 2 6'
J
M e33'
\
Me 3 3
Figure 2. Molecular structure of [(CSMeS),Sm(p-C1)]3(1). Carbon atoms have been reduced to dots for clarity.
Figure 3. Structure of the ((C5Me,)2C1Sm(p-C1)Sm(C5Me5)2[p,~4-Me(OCH,CH2)40Me]Sm(C,Me5)2~+ cation. C,Me, carbon atoms are shown as dots for clarity.
is exactly planar and has approximate C2, symmetry with Sm(2) and Cl(4) on the C, axis. Inspection of the three independent Sm-Cl distances, 2.849 (7), 2.892 (7), and 2.887 (3) A, the two C1-Sm-C1 angles, 81.5 (2)' and 84.0 ( 2 ) O , and the two SmC1-Sm angles, 154.0 (3)O and 158.2(3)O (Table V), shows that the Sm,(p-Cl), unit has nearly D,,symmetry. The pairs of C,Me, rings associated with each samarium atom have a staggered orientation with (ring a carbon)-(centroid a)-(centroid b)-(ring b carbon) torsional angles in the 35-47' range. Structure of (CSMeS)loSm,C15[Me(OCH2CH,),00Me]. In the presence of a trace amount of tetraglyme, (C5Me5)2SmC1units crystallize from toluene in a complex structure which has four different Sm3+coordination environments. These can be described by the detailed formula {(C,Me,)2CISm(p-CI)Sm(C5Me5)2IIL,~~-M~(OCH~CH~)~OM~IS~(C~M~S)Z)+( t(C5Me5),C1Sm12 ( ~ Cl)]-. The cation, shown in Figure 3, contains a [(C,Me,),Sm]+ unit ligated by three oxygen atoms of the tetraglyme molecule along with a neutral (C,Me,)2C1Sm(p-C1)Sm(C,Me,), unit attached to another oxygen atom of the tetraglyme. The remaining oxygen atom in tetraglyme is not coordinated to a metal atom. The anion in this system, shown in Figure 4, is like the neutral (C5Me5)2C1Sm(p-C1)Srn(C5MeS),-O(tetraglyme) unit in the cation except that a terminal chloride ligand replaces the tetraglyme oxygen atom. In each of these bimetallic samarium units
3932 J . Am. Chem. SOC.,Vol. 109, No. 13, 1987
Evans et ai.
Table IV. Final Fractional Coordinates for (C5Me5),oSm5C15[Me(OCH2CH2)40Me] atom
xla
Ylb
ZIC
0.4036 ( I ) 0.2628 ( I ) 0.3873 (1) 0.3381 (1) 1.1403 (1) 0.3 180 (5) 0.3842 (5) 0.5389 (5) 0.2486 (6) 0.1979 (6) 1.020 (3) 1.088 (2) 1.117 (4) 1.211 (4) 1.217 (2) 1.299 (3) 1.300 (3) 1.279 ( I ) 1.296 (3) 1.387 (2) 1.393 (1) 1.474 (2) 1.482 (2) 1.453 ( I ) 1.482 (3) 0.446 (2) 0.367 (2) 0.331 (2) 0.387 (2) 0.457 (2) 0.510 (3) 0.329 (2) 0.241 (3) 0.370 (3) 0.534 (3) 0.405 (2) 0.446 (2) 0.397 (3) 0.326 (3) 0.329 (3) 0.440 (3) 0.535 (3) 0.411 (3) 0.247 (3) 0.257 (2) 0.116 (3) 0.103 (3) 0.126 (2) 0.153 (2) 0.146 (2) 0.084 (3) 0.081 (5) 0.130 (3) 0.181 (3) 0.146 (3) 0.363 (2) 0.337 (2) 0.362 (2) 0.411 (2) 0.408 (2) 0.355 (3) 0.295 (3) 0.357 (2)
0.305 60 (7) 0.477 85 (7) 0.248 07 (8) 0.361 21 (8) 0.559 55 (7) 0.3844 (3) 0.3067 (4) 0.3479 (4) 0.5068 (4) 0.3740 (4) 0.655 (2) 0.624 ( I ) 0.629 (2) 0.618 (2) 0.5771 (9) 0.562 (2) 0.510 (2) 0.512 ( I ) 0.466 (2) 0.467 (2) 0.417 (1) 0.412 (2) 0.362 (2) 0.319 ( I ) 0.312 (2) 0.265 ( I ) 0.269 ( I ) 0.237 (1) 0.211 (2) 0.228 (2) 0.286 (2) 0.300 (2) 0.234 (2) 0.166 (2) 0.204 (2) 0.263 (2) 0.305 (2) 0.344 (2) 0.329 (2) 0.275 (2) 0.211 (2) 0.306 (2) 0.406 (2) 0.358 (2) 0.241 (2) 0.504 (2) 0.476 (2) 0.429 (2) 0.440 (2) 0.490 (2) 0.549 (2) 0.445 (3) 0.369 (2) 0.407 (2) 0.518 (2) 0.510 (2) 0.554 (2) 0.555 (1) 0.508 ( I ) 0.485 (2) 0.497 (2) 0.601 (2) 0.595 (2)
0.54896 (9) 0.57243 (9) 1.17400 (9) 0.9698 ( I ) 1.21279 (9) 0.5613 (5) 1.0805 (4) 0.6060 (5) 0.4659 (5) 0.9584 (6) 1.235 (3) 1.263 (2) 1.319 (2) 1.359 (2) 1.320 (1) 1.355 (1) 1.335 (2) 1.268 ( I ) 1.247 (2) 1.265 (3) 1.242 ( I ) 1.258 (2) 1.226 (2) 1.249 ( I ) 1.314 (2) 0.660 (2) 0.638 (1) 0.593 (2) 0.581 (2) 0.620 (2) 0.715 (2) 0.672 (2) 0.561 (2) 0.540 (2) 0.624 (2) 0.450 (2) 0.459 (2) 0.447 (2) 0.435 (2) 0.433 (2) 0.445 (2) 0.472 (2) 0.446 (2) 0.408 (2) 0.407 (2) 0.546 (2) 0.501 (3) 0.535 (2) 0.605 (2) 0.605 (2) 0.498 (3) 0.444 (4) 0.532 (3) 0.661 (3) 0.657 (2) 0.685 (2) 0.649 (2) 0.609 (2) 0.613 (2) 0.663 (2) 0.744 (2) 0.658 (2) 0.564 (2)
the four C 2a(F0). The carbene ligand is bound to a basal iron atom, and the carbene carbon lies within the Fe3 plane. The carbene and nitrene ligands in 9 couple to form the imidate PhN=C(OEt)Ph when 9 is exposed to air or allowed to stand in solution for prolonged periods under CO or N2 atmospheres. A crossover experiment showed this coupling to be strictly intramolecular. Similar nitrene-benzoyl coupling from 7 gives benzanilide, and the methoxycarbonyl and nitrene ligands in 8 couple to give methyl N-phenylcarbamate when the clusters are oxidatively degraded with [FeCpJ'. The latter reaction models mechanistic suggestions previously made for the M3(CO),, (M = Fe, Ru) catalyzed carbonylation of PhN02 to yield carbamates. The bis(ph0sphinidene) cluster Fe3(p3-PPh)2(C0)9(2) also reacts with PhLi to yield a benzoyl derivative, [ Fe3(~3-PPh)2(CO),(C(01Ph)]-.However, addition of EtOTf to this species does not result in a carbene cluster analogous to 9, but instead phosphinidene-carbene coupling occurs to give Fe3(p3-PPh)(q3-PhPC(OEt}Ph)(C0)9 which has been structurally characterized: P i , a = 9.241 (2) A, b = 10.233 (3) A, c = 19.564 (5) A, LY = 84.53 (2)O, 0 = 84.43 (2)O, y = 76.41 (2)O, V = 1784.7 (8) A', Z = 2, R = 0.0557, R, = 0.0602 for 3710 reflections with F, > 3a(F,,). The phosphorus atom of the P , - P ~ P C ( O E ~ligand J P ~ bridges two iron atoms, and the ethoxy-substituted carbon is attached to the third iron atom.
The chemistry of low-valent metal carbene complexes has been extensively investigated, and many such compounds have found impressive synthetic utility.' In contrast, the chemistry of nitrene ligands bound to low-valent metals remains relatively even though such ligands have been invoked as intermediates in several catalytic reaction^.^ The lack of chemical studies is in part due to the low stability of mononuclear carbonyl nitrene complexes such as (CO)5Cr=NPh,4 a particularly interesting species in view of the large number of synthetic applications of 'The Pennsylvania State University. 1University of Delaware.
0002-7863/87/ 1509-3936$01.50/0
its carbene analogue.lc Like many reactive organic ligands, stabilization of nitrenes by low-valent organometallics can be ( I ) (a) Brown, F. J. Prog. Inorg. Chem. 1980, 27, I . (b) Casey, C. P. React. Intermed. 1985, 3 , 109. (c) Kreissl, F. R.; Doetz, K. H.; Weiss, K. In Transition Metal Carbene Complexes; Verlag Chemie: Weinheim, 1983. (d) Collman, J. P.; Hegedus, L. S.Principals and Applications of Organotransition Metal Chemistry, University Science Books: Mill Valley, CA, 1980; pp 91-103. (2) For reviews, see: (a) Nugent, W. A,; Haymore, 8. L. Coord. Chem. Rev. 1980, 31, 123-175. (b) Cenini, S.;La Monica, G. Inorg. Chim. Acta 1976, 18, 279.
0 1987 American Chemical Society
