Volume 5, Number zyxwvu 7, zyxwv July 1986 0 Copyright 1986 American Chemical Society Synthesis and X-ray Crystal Structure of Bls(pentamethylcyclopentadieny1) Complexes of Samarium and Europium: (C,Me,),Sm and (C,Me,)2Eu William J. Evans," Laura A. Hughes, and Timothy P. Hanusa Department of Chemistry, University of California, Iwlne, California 92717 Rece1ve.d October 7, 1985 (C,Me,@m(THF), can be desolvated at zyxwvut 75 'C under high vacuum to form the green complex (C&e&$m, which sublmes at 85 OC and 1Oa torr. Single crystals grown by sublimation crystallize in the space group zyx R,/n with a zyxwvutsr = 9.815 (3) A, zyxwvutsrqp b = 13.436 (9) A, c = 14.163 (8) A, zyxwvu 6 = 94.98 (4)', v = 1861 (2) A3, and Deal,.. = 1.500 g cm-3 for 2 = 4. Least-squares refinement on the basis of 2636 unique observed reflections (I > 34) converged to a final R = 0.035. The molecule exhibits a bent structure with a (ring centroid)- Sm-(ring centroid) angle of 140.1O and an average Sm-cyclopentadienyl carbon distance of 2.79 (1) A. Repeated sublimation of (C5Me5),Eu(THF) at 70 "C under high vacuum yields the deep red unsolvated complex (C6Me6)2Eu. X-ray quality crystals grown by resublimation form in the s ace group P2,/n with a = 9.838 (4) A, b = 13.443 (4) A, c = 14.174 (3) A, 6 = 95.03 (2)', v = 1867 (2) &, and.D,dcd = 1.503 g cmS for 2 = 4. Full-matrix least-squares refinement on the basis of 2543 unique reflections (I 1 3a (I)) converged to R = 0.055. (CSMe6),Eu is isomorphous and isostructural with (C6Me5),Srn. It possesses a bent metallmne structure with a (ring centroid)-Eu-(ring centroid) angle of 140.3' and an average Eu-C(q5) distance of 2.79 (1) A. Introduction During the past several years we have investigated the low-valent organometallic chemistry of the lanthanide elements by both metal vapor and solution synthesis methods.2-8 These efforta have led to the discovery of a new family of soluble (pentamethylcyclopentadieny1)sa- marium(I1) complexes which includes the monomeric (C6Me6)2Sm(THF),species (n = 0,B 1,' or 28) and the halide-bridged dimer [ (CSMe5)Sm(p-I)(THF)2]2.7 These molecules have permitted the first detailed studies on highly reactive divalent organosamarium systemsg and (1) Alfred P. Sloan Research Fellow. (2) Evans, W. J. J. Organornet. Chem. 1983,250,217-226 and refer- ences therein. (3) Evans, W. J. In The Rare Earths in Modern Science and Tech- nology; McCarthy, G. J., Rhyne, J. J., Silber, H. E., Eds.; Plenum Press: New York, 1982; Vol. 3, pp 61-70 and references therein. (4) Evans, W. J.; Engerer, S. C.; Coleson, K. M. J. Am. Chem. SOC. 1981,103,66124677. (5) Evans, W. J.; Bloom, I.; Engerer, S. C. J. Catal. 1983,84,468-476. (6) Evans, W. J.; Hughes, L. A.; Hanuea, T. P. J. Am. Chem. Soc. 1984, 106,42104272. (7) Evans, W. J.; Grate, J. W.; Choi, H. W.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J. Am. Chem. Soc. 1985,107,941-946. (8) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J. Am. Chem. SOC. 1981,103,6507-6508. (9) Sm(1II) + e - Sm(I1); @ = -1.5 V vs. N H E Morse., L. R. Chem. Rev. 1976, 76,827. have opened an area of organolanthanide chemistry.which had been inaccessible because of the insolubility of the previously reported organometallic Sm(I1) X-ray crystal studies of (C5Me6)2Sm(THF)28 and [(C5Me6)Sm (P-I)(THF)~]~ provided basic structural in- formation on this new class and revealed structures con- sistent with established structural patterns.13 We recently determined the X-ray crystal structure of the solvent-free complex decamethylsamarocene, (C6Me6)2Sm,6 which proved to possess an unusual bent metallocene geometry (Figure la). Traditionally, the bonding in organo- lanthanide complexes has been thought to be predomi- nantly ionic due to the limited radial extension of the 4f valence orbitals,14 and organolanthanide structures are thought to be controlled to a large degree by electrostatic factors.13 For an ionic complex of two C5Me5-anions and (10) Both [(C6H&Sm(THF) ] and [(CHsC6H1)2Sm(THF),],'1 are insoluble in all solvents with wf&h they do not react. (11) (a) Watt, G. W.; Gillow, E. W. J. Am. Chem. Soc. 1969, 91, 775-776. (b) Namy, J. L.; Girard, P.; Kagan, H. B. Nouv. J. Chim. 1981, (12) Evans, W. J.; Zinnen, H. A., unpublished results. (13) Raymond, K. N.; Eigenbrot, C. W., Jr. Acc. Chem. Res. 1980,13, (14) Freeman, A. J.; Watson, R. E. Phys. Rev. 1962,127, 2058-2075. 5,479-484. 276-283. Crosswhite, H. M.; Paszek, A. P., personal communication, 1981. 0276-7333/86/2305-1285$01.50/0 0 1986 American Chemical Society