J . Am. Chem. SOC.1985, 107, 941-946
94 1
Solution Synthesis and Crystallographic Characterization of the Divalent Organosamarium Complexes (CSMeS)2Sm( THF)* William J. Evans,*la,bJay W. Grate,lb Henry W. Choi,lb Ira Bloom,lb William E. Hunter," and Jerry L. Atwood*lc Contribution from the Departments of Chemistry, The University of California, Irvine, Irvine, California 9271 7 , and The University of Alabama, University, Alabama 35486. Received July 16, 1984
Abstract: The reaction of Sm12 in THF solution with a slight excess of 2 equiv of KC5Me5yields (C5Me5)2Sm(THF)2 (I) in high yield and purity. Reaction of I with an equimolar quantity of Sm12forms [(C,Me5)sm(p-I)(THF),1, (II), which can also be prepared from the 1:l stoichiometric reaction of SmI, and KC5MeS. Both I and I1 have been characterized by spectral, chemical, and X-ray crystallographic methods. I crystallizes from THF in the triclinic space group Pi with a = 15.155 ( 6 ) A, b = 16.141 (6) A, c = 16.179 (6) A, a = 55.92 (3)O, p = 65.13 (3)O, y = 62.18 (3)O, and 0,= 1.33 g cm13 for Z = 4. Least-squares refinement on the basis of 3949 observed reflections led to a final R value of 0.061. The molecule has a bent metallocene structure in which the two cyclopentadienyl ring centroids and the two THF oxygen atoms roughly describe a tetrahedral coordination geometry. The average Sm-C(ring) distance is 2.86 (3) A. The average Sm-0 distance is 2.64 A. I1 crystallizes from THF under hexane diffusion in the monoclinic space group P2,/n with u = 12.708 (6) A, b = 13.454 ( 6 ) A, c = 14.859 (6) A, p = 112.37 (4)O, and D, = 1.57 g cm-3 for Z = 2 (dimers). Least-squares refinement on the basis of 1577 observed reflections led to a final R value of 0.053. The two (C5MeS)(THF),Sm moieties in the molecule are bridged by iodine ligands via a planar Sm2(pI), unit with the cyclopentadienyl ring on one side of the plane and the THF molecules on the other side. The two distinct Sm-(p-I) distances are 3.356 (2) and 3.459 (2) A, the average Sm-C(ring) distance is 2.81 (2) A, and the Sm-0 distances average 2.64 A.
In recent years, the organometallic chemistry of the lanthanide metals in low oxidation states has been actively investigated and a variety of new complexes and reactivity patterns have been discovered.2-10 These low-valent studies have involved the zerovalent metals in the elemental state, using metal-vapor techniques, as well as the complexes of the three lanthanide metals that have divalent states readily accessible under "normaln solution reaction conditions, Le., Eu, Yb, and Sm. Although Sm(I1) is the most reactive of these divalent lanthanides [Sm(III) e Sm(I1):
+
-
,
previously investigated because the only known divalent organosamarium complexes, [ ( C S H s ) 2 S m ( T H F ) , ] , ' 2 ~ ~ 3and [(CH3C5H4)2Sm(THF),],,'4are insoluble. Recently, however, we reported the synthesis of the first soluble organosamarium(I1) complex, (CSMeS),Sm(THF), (I), starting from zerovalent samarium vapor (eq l).3 As anticipated, this S m (vapor)
+ C5Me5H (-120
"C)
-THF
(C5Me5) 2Sm(THF)2 ( 1 I
(1) (a) Alfred P. Sloan Research Fellow. (b) University of California, Irvine. (c) University of Alabama. (2) (a) Evans, W. J.; Engerer, S. C.; Neville, A. C. J . Am. Chem. SOC. 1978,100,331-333. (b) Evans, W. J.; Wayda, A. L.; Chang, C. W.; Cwirla, W. M. J . Am. Chem. SOC.1978, 100, 333-334. (c) Zinnen, H. A,; Evans, W. J.; Pluth, J. J. J . Chem. Soc., Chem. Commun. 1980, 810-812. (d) Evans, W. J.; Engerer, S. C.; Neville, A. C. J . Chem. SOC.,Chem. Commun. 1979, 1007-1008. (e) Evans, W. J.; Engerer, S. C.; Piliero, P. A.; Wayda, A. L. "Fundamentals of Homogeneous Catalysis"; Tsutsui, M., Ed.; Plenum Press: New York, 1979; Vol. 3, 941-952. (0 Evans, W. J.; Engerer, S. C.; Coleson, K. M. J . Am. Chem. Soc. 1981,103,6672-6677. (g) Evans, W. J.; Coleson, K. M.; Engerer, S. C. Inorg. Chem. 1981, 20,4115-4119. (h) Evans, W. J. In 'The Rare Earths in Modern Science and Technology"; McCarthy, G. J., Rhyne, J. J., Silber, H. E., Eds.; Plenum Press: New York, 1982; Vol. 3, pp 61-70. (i) Evans, W. J. J . Organomet. Chem. 1983,250,217-226. 0') Evans, W. J.; Bloom, I.; Engerer, S. C. J . Catal. 1982, 104, 2008-2014. (3) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J . Am. Chem. SOC.1981, 103, 6507-6508. (4) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J. Am. Chem. SOC.1983, 105, 1401-1403. ( 5 ) Evans, W. J.; Hughes, L. A.; Hanusa, T. P. J . Am. Chem. SOC.1984, 106, 4270-4272. (6) Watson, P. L. J . Chem. SOC.,Chem. Commun. 1980, 652-653. (7) (a) Tilley, D. T.; Andersen, R. A.; Spencer, B.; Ruben, H.; Zalkin, A,; Templeton, D. H. Inorg. Chem. 1980, 19, 2999-3003. (b) Tilley, T. D.; Andersen, R. A. J . Am. Chem. SOC.1982, 104, 1772-1774. (c) Tilley, T. D.; Andersen, R. A,; Zalkin, A. J . Am. Chem. SOC.1982, 104, 3725-3727. (d) Tilley, T. D.; Andersen, R. A.; Spencer, B.; Zalkin, A. Inorg. Chem. 1982, 21, 2647-2649. (8) Lappert, M. F.; Yarrow, P. I. W.; Atwood, J. L.; Shakir, R.; Holton, J. J . Chem. Soc., Chem. Commun. 1980, 987-988. (9) Deacon, G. B.; Koplick, A. J.; Raverty, W. D.; Vince, D. G. J . Orgunomet. Chem. 1979, 282, 121-141 and references therein. (10) (a) Girard, P.; Namy, J. L.; Kagan, H. B. J. Am. Chem. SOC.1980, 102, 2693-2698. (b) Souppe, J.; Danon, L.; Namy, J. L.; Kagan, H. B. J. Organomet. Chem. 1983, 250, 227-236 and references therein. I
-1.5 VI," its chemistry in organometallic systems had not been
,
complex reacts rapidly with a variety of substrates and has provided access to a wealth of new organosamarium c o m p l e x e ~ . ~ - ~ J ~ [(CSMeS)2SmH]2,4 and These include [(C5MeS)2Sm]2(C,Hs)2C2,4 (CSMe5)2Sm,5complexes that are active in homogeneous hydrogenation catalysis4J6and in C O activation." Although the original synthesis of I was achieved on a preparative scale,3 a rotary metal vaporization reactor was required. W e now report the synthesis of I by solution methods, a result that should make soluble divalent organosamarium complexes more generally available for investigation. Considering recent interest in the use of divalent lanthanides in organic synthesis,I0J8 this may be particularly important. In the course of developing a solution synthesis for I, we have discovered a new, soluble, divalent, organosamarium complex, (11) Vs. NHE: Morss, L. R. Chem. Reu. 1976, 76, 827. (12) Watt, G. W.; Gillow, E. W. J . Am. Chem. SOC.1969, 91, 775-776. (13) Namy, J. L.; Girard, P.; Kagan, H. B. Nouu. J . Chim. 1981, 5 ,
A79-AAA .- ..
(14) Evans, W. J.; Zinnen, H. A,, unpublished results. (15) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. Organometallics, in press. (16) Evans, W. J.; King, R. E., 111; Hanusa, T. P., manuscript in preparation. (17). Evans, W. J.; Grate, J. W.; Hughes, L. A,; Zhang, H.; Atwood, J. L., unpublished results. (18) White, J. D.; Larson, G. L. J . Org. Chem. 1978, 43, 4555-4556. Ananthanarayan, T. P.; Gallagher, T.; Magnus, P. J . Chem. Soc., Chem. Commun. 1982, 709-710. Girard, P.; Couffignal, R.; Kagan, H. B. Tetruhedron Lett. 1981, 22, 3959-3690. Yokoo, K.; Yamanaka, Y.; Fukagawa, T.; Taniguchi, H.; Fujiwara, U. Chem. Lett. 1983, 1301-1302.
0 1985 American Chemical Society
942 J . Am. Chem. SOC.,Vol. 107, No. 4, 1985 [(C5Me5)Sm(pI)(THF),1, (11) which is potentially important in several respects. Complex I1 is t h e first Sm(I1) organometallic compound t h a t has a reactive site, t h e halide ligand, suitable for further modification of t h e Sm(I1) coordination e n ~ i r o n m e n t . ’ ~ For example, reaction of I1 with lithium alkyl reagents may provide divalent s a m a r i u m alkyl complexes t h a t may be hydrogenolyzable22,23to f o r m divalent s a m a r i u m hydride species. T h e new complexes would combine a reactive lanthanide alkyl or hydride moiety22 with t h e strong one-electron reducing capacity of the Sm(I1) center. Complex I1 also completes t h e series (C5Me5)2Sm(THF)2, [(C,Me,)sm(ll-I)(THF)212, a n d SmIZ(THF),, a set of complexes t h a t should allow precise variation of divalent s a m a r i u m reactivity by varying t h e steric bulk of t h e ligands surrounding t h e m e t a l center.24 We report here the synthesis of I and I1 as well as full details of the X-ray crystal structure determinations of these compounds, which are t h e first crystallographically characterized organosamarium(I1) c ~ m p l e x e s . ~
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 by using Schlenk, vacuum-line, and glovebox (Vacuum/Atmospheres HE-553 Dri Lab) techniques. Materials. Pentane and hexane were washed with sulfuric acid, dried over MgS04, and distilled from potassium benzophenone ketyl solubilized with tetraglyme. Toluene and T H F were distilled from potassium benzophenone ketyl. THF-d, and benzene-d, were vacuum transferred from potassium benzophenone ketyl. CsMe,H was prepared by published proceduresz5 and converted to KCSMe5with K H in THF.,, Solutions of SmI,(THF), were prepared from excess Sm metal (Research Chemicals, Phoenix, AZ) and l,2-C2H412in T H F s ~ l u t i o n . ’(This ~ reaction is quantitative in l,2-C2H412.”) Evaporation of the solutions of Sm12 resulting from this preparation yields a free-flowing blue-black powder formulated as Sm12(THF), on the basis of its weight and the moles of 1,2-C2H412used. Physical Measurements. Infrared spectra were obtained on a Perkin-Elmer 283 spectrometer. ‘H and I3C N M R spectra were obtained on a Bruker WM-250 spectrometer. Chemical shifts were assigned relative to C,D5H, 7.15 ppm, for spectra in benzene-d,, or relative to proteo-THF, 1.72 ppm, for spectra in THF-d,. Magnetic susceptibility measurements were obtained on the Bruker 250-MHz N M R spectrometer by the Evans method.27 Complete elemental analyses were obtained from Analytische Laboratorien, Engelskirchen, Germany. (C5Me5),Sm(THF), (I). In the glovebox, KC5Me5 (5.43 g, 31.2 mmol) was added to a stirring solution of Sm12(THF), (7.78 g, 14.2 mmol) in 75 mL of T H F in a 125-mL Erlenmeyer flask. The solution color rapidly changes from blue-green to purple as off-white solids (KI) are formed. After 4 h at ambient temperature, the T H F was removed by rotary evaporation, and 100 mL of toluene was added. The resulting solution of I with suspended potassium salts was stirred vigorously for 10 h and then filtered. The solvent was removed from the filtrate by rotary evaporation leaving solid (C,Me,),Sm(THF),,, where 1 5 n 5 2 . The degree of solvation is conveniently monitored by integration of the absorptions in the N M R spectrum in benzene-d6. Dissolving this solid in T H F and then removing the solvent by rotary evaporation yield the
(19) Complex I1 is analogous in importance to bis(cyc1opentadienyl)lanthanide(ha1ide) complexes in trivalent lanthanide chemistry.20~21 (20) Evans, W. J. In “The Chemistry of the Metal-Carbon Bond”; Hartley, F. R., Patai, S., Eds.; Wiley: New York, 1982; Chapter 12, pp 489-537. (21) Marks, T. J.; Ernst, R. D. In “Comprehensive Organometallic Chemistry”;Wilkinson, G.et. al., Eds.; Pergamon Press: 1982; Vol. 3, Chapter 21. (22) Evans, W. J.; Meadows, J. H.; Wayda, A. L.; Hunter, W. E.; Atwood, J. L. J . A m . Chem. SOC.1982, 104, 2008-2014. (23) Evans, W. J.; Meadows, J. H.; Hunter, W. E.; Atwood, J. L. J . Am. Chem. SOC.1984, 106, 1291-1300. (24) Evans, W. J. Ado. Orgunomef.Chem., in press. (25) Threlkel, R. S.; Bercaw, J. E. J . Orgunomet. Chem. 1977, 136, 1-5. Manriquez, J. M.; Fagan, P. J.; Schertz, L. D.; Marks, T. J. Inorg. Synth. 1982, 21, 181-185. Kohl, F. X.;Jutzi, P. J . Orgunomef.Chem. 1983, 243, 119-1 21. (26) Watson, P. L.; Whitney, J. F.; Harlow, R. L. Inorg. Chem. 1981, 20, 3271-3278. (27) Evans, D. F. J . Chem. SOC.1959, 2003-2005. Becconsall, J. K. Mol. Phys. 1968, I S , 129-139.
Evans
et
ai.
Table I. Crystal Data and Summary of Intensity Data Collection and Structure Refinement for (CcMe5),Sm(THF), compound Sm02C28C46 565.05 Mr space group pi cell constants 15.155 (6) a, A 16.141 (6) b, A 16.179 (6) c, A 55.92 (3) a, deg 65.13 (3) A deg 62.18 (3) 7,deg cell vol, A’ 2829.9 molecules/unit cell 4 p(calcd), g cm-’ 1.33 fi(calcd), cm-l 21.3 radiation Mo Ka 0.20 X 0.25 X 0.30 max crystal dimensions, mm scan width 0.8 O.Z(tan 6’) standard reflections 200 020 002
