DOUBLE-DIMETHYLSILYL-BRIDGED DICYCLOPENTADIENYL GROUP-4 METAL-COMPLEXES - X-RAY MOLECULAR-STRUCTURES OF M[(ME2SI)2(ETA-5-C5H3)2]CL2 (M=TI, ZR) AND (TICL3)2(MU-[(ME2SI)2(ETA-5-C5H3)2])

The synthesis of the dithallium salt of the double-dimethylsilyl-bridged dicyclopentadienyl ligand T12[(Me2Si)2(C5H3)2] (1) is described. The reaction of 1 with 1 equiv of MCl4 (M = Ti, Zr, Hf) by refluxing their toluene solutions leads to the metallocene-type species M[Me2Si)2-(eta5-C5H3)2]Cl2 (M = Ti (2), Zr (3), Hf (4)) in 65-70% yields. Complexes 2-4 are methylated by MeLi or MeMgCl leading to the dimethylmetallocenes M[(Me2Si)2(eta5-C5H3)2]Me2 (M = Ti (5), Zr (6), Hf (7)) in 70% yields. When the same reaction of 1 with TiCl4 is carried out in a 1:2 molar ratio at room temperature, the monocyclopentadienyl-type species (TiCl3)2{mu-[(Me2-Si)2-(eta5C5H3)2]} (8) is obtained. The H-1 and C-13 NMR data are discussed in terms of establishing useful criteria to distinguish between species containing chelated and bridging cyclopentadienyl ligands and comparing electronic effects due to the double-silyl-bridged system. The X-ray crystal structures of complexes 2, 3, and 8 are described. Complexes 2 and 3 are metallocene-type compounds: 2 crystallizes in the monoclinic space group P2(1)/n with a = 9.483(2) angstrom, b = 11.558(6) angstrom, c = 14.892(5) angstrom, beta = 91.92(1)-degrees, V = 1631(1) angstrom3, and Z = 4. 3 crystallizes in the same space group with a = 9.392(3) angstrom, b = 13.863(4) angstrom, c = 13.376(4) angstrom, beta = 101.82(1)-degrees, V = 1704(1) angstrom3, and Z = 4. Compound 8 is a dinuclear complex with the metals in trans position relative to the ligand plane. 8 crystallizes with a toluene molecule in the monoclinic space group P2(1)/c with a = 11.339(2) angstrom, b = 11.292(3) angstrom, c = 14.006(3) angstrom, beta = 105.08(1)-degrees, V = 1732(1) angstrom3, and Z = 4.