ISOLATION AND STRUCTURAL CHARACTERIZATION OF CIS-FORMS AND TRANS-FORMS OF [(ETA(5)-C(5)ME(5))TICL2](2)[MU-ETA(5)-ETA(5)-(C5H3)(2)(SIME(2))(2)]

Deprotonation of 4,4,8,8-tetramethyltetrahydro-4,8-disila-s-indacene with 2 equiv of n-BuLi in THF provides the silicon-bridged dianion Li-2[mu-(C5H3)(2)(SiMe(2))(2)], which was reacted with eta(5)-(C(5)Me(5))TiCl3 to provide the bimetallic complexes trans- and cis-[(eta(5)-C(5)Me(5))TiCl2](2)[mu-eta(5):eta(5)-(C5H3)(2)(SiMe(2))(2)] (1, 2), respectively, in approximately a 1:1 ratio. The trans-form, 1, precipitates from the reaction medium and thus could be separated from the cis-isomer, 2. Reaction of the dianion with eta(5)-(C5H5)TiCl3 produced only trans- [(eta(5)-C5H5)TiCl2](2)[mu-eta(5):eta(5)-(C5H3)(2)(SiMe(2))(2)] (3). Reaction of 1-3 with 4 equiv of MeLi provided the corresponding tetramethyl derivatives. The solid state structures of 1 and 2 were determined by single-crystal X-ray analysis. Compound 1 crystallizes in the monoclinic space group P2(1)/c with a = 14.967(2) Angstrom, b = 13.772(2) Angstrom, c = 8.983(2) Angstrom, beta = 105.92 degrees, and Z = 2. Compound 2 crystallizes in the tetragonal space group P4(3)2(1)2 with a = b = 10.648(2) Angstrom, c = 32.030(8) Angstrom, and Z = 4. The central ring of the disilaindacenyl ligand is planar in 1 with the two metal units bound to the outer Cp units but on opposite sides of the ligand faces. The central ring in 2 exhibits a boat conformation with both metal units bound to the convex face of the ligand. The Ti ... Ti distance in trans-1 is 6.94 Angstrom, shorter than the 7.33 Angstrom observed in cis-2. A summary and comparison of the four structural types observed for bimetallic complexes of the type [ML(n)](2)[mu-eta(5):eta(5)-(C5H3)(2)(SiMe(2))(2)] is presented.