Synthesis and structural study of the ate-complex rac-(CH3)2C(C5H3-3-Si(CH3)3)2Yb(μ2-Cl)2Li(OEt2)2 and the polymeric compound {rac-(CH3)2C(C5H3-3-Si(CH3)3)2Yb[(μ2-H)2B(μ2-H)2]2Li(THF)2}∞

The ate-complex rac-(CH3)(2)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-trimethylsilylcyclopentadienyl [(CH3)(2)C(C5H3-3-Si(CH3)(3))(2)Li](2) and ytterbium (111) chloride. The reaction between 1 and a 50% excess of LiBH4 in THF afforded the borohydride ansa-ytterbocene complex {rac-(CH3)(2)C(C5H3-3-Si(CH3)(3))Yb[mu(2)-H)(2)B(mu(2)-H)(2)](2)Li(THF)(2)}(infinity) (2). Crystals of complex 1 are monoclinic: 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, respectively. 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)degrees, 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 Elsevier Science S.A. All rights reserved.