MONOCYCLOPENTADIENYL-TYPE TITANIUM COMPLEXES WITH THE [ETA-5-ETA-5-(C5H4)2SIME2]2- LIGAND - X-RAY CRYSTAL-STRUCTURE OF [(TICL)2(MU-2-O)(MU-2-ETA-5-ETA-5-(C5H4)2SIME2(]2(MU-2-O)2 - THE 1ST EXAMPLE OF A NONPLANAR TI4O4 CORE

The thallium compound [TIA(C5H4)2SiMe2}] (1) was prepared by reaction of (C5H5)2SiMe2 with thallium ethoxide in diethyl ether at -78-degrees-C. Reaction of 1 with 2 equiv of TiCl4 produces the dinuclear compound [(TiCl3)2{mu2-eta5-eta5-(C5H4)2SiMe2}] (2). Controlled hydrolysis of 2 gives the dinuclear mu-oxo compound [(TiCl2)2(mu2-0){mu2-eta5-eta5- (C5H4)2SiMe2}] (3). ComPlex 3 reacts with AlEtCl2 to regenerate quantitatively complex 2. When 2 or 3 is treated with water in acetonitrile,the tetranuclear mu-oxo complex [(TiCl)2(mu2-0){mu2-eta5-eta5-(C5H4)2SiMe2}]2(mu2-0)2 (4) is obtained. The crystal and molecular structure of 4 has been determined by X-ray diffraction methods. 4 crystallizes in a triclinic space group P1BAR with a = 9.508 (1) angstrom, b = 9.789 (1) angstrom, c = 9.808 (1) angstrom, alpha = 116.09 (1)-degrees, beta = 94.62 (1)-degrees, gamma = 97.97 (1)-degrees, V = 801.5 angstrom3, Z = 1, and d(calc) = 1.595 g CM-3. The structure can be formally regarded as the dimer of the hypothetical dinuclear fragment [(TiCl)2(mu2-0){mu2-eta5-eta5-(C5H4)2-SiMe2}(-O)] with a nonplanar ''Ti4O4'' core, not previously reported for other similar Ti4Ox systems.