SYNTHESIS AND STRUCTURAL STUDY OF THE ATE-COMPLEX )C(C5H3-3-SI(CH3)(3))(2)YB(MU(2)-CL)(2)LI(OET2)(2) AND THE POLYMERIC COMPOUND (MU(2)-H)(2)B(MU(2)-H)(2)](2)LI(THF)(2))(INFINITY)

The ate-complex )C(C5H3-3-Si(CH3)(3))(2)Yb(mu(2)-Cl)(2)Li(OEt2)(2) (1) was obtained in ether from the dilithium salt of 2,2-bis(3-trimethyls ilylcyclopentadienyl [(CH3)(2)C(C5H3-3-Si(CH3)(3))(2)Li](2) and ytterb ium (111) chloride. The reaction between 1 and a 50% excess of LiBH4 i n THF afforded the borohydride ansa-ytterbocene complex [mu(2)-H)(2)B( mu(2)-H)(2)](2)Li(THF)(2)}(infinity) (2). Crystals of complex 1 are mo noclinic: a = 11.680(2) Angstrom, b = 21.823(4) Angstrom, c = 13.843(3 ) Angstrom, beta = 99.03(3)degrees, D-calc = 1.360 g cm(-3), P2(1)/c, Z = 4. Average Yb-Cl, Yb-Cp bond lengths and Cl-Yb-Cl, Cp-Yb-Cp angles are equal to 2.57 and 2.30 Angstrom, 85.9 and 113.6 degrees, respecti vely. Crystals of compound 2 are triclinic: a = 7.0030(10) Angstrom, b = 11.370(2) Angstrom, c = 11.895(2) Angstrom, alpha = 106.42(3)degree s, beta = 95.24(3) degrees, beta = 98.91(3) degrees, D-calc = 1.250 g cm(-3), P(1)over-bar, Z = 1. Average Yb-B, Yb-Cp bond lengths and B-Yb -B, Cp-Yb-Cp angles are equal to 2.59 and 2.33 Angstrom, 96.3 and 111. 0 degrees, respectively. The BH4-groups in compound 2 were found to be tetradentate and linked with six-coordinate lithium atoms via (mu(2)- H)-bridges which resulted in a polymeric chain structure. (C) 1998 Els evier Science S.A. All rights reserved.