CATIONIC TITANIUM(IV) COMPLEXES VIA HALIDE ABSTRACTION FROM [TI(C5H5)CL-3] - CRYSTAL AND MOLECULAR-STRUCTURE OF [TI(C5H5)(MECN)(5)][SBCL6](3)CENTER-DOT-2MECN

Treatment of [Ti(cp)Cl3](cp = eta(5)-C5H5) with SbCl5 as chloride abstractor in acetonitrile provided hexachloroantimonate(V) salts of [Ti(cp)Cl-2](+), [Ti(cp)Cl](2+) and [Ti(Cp)](3+) respectively. With 1:1 stoichiometry red-brown crystals of [Ti(cp)Cl-2(MeCN)(3)][SbCl6] 1 are obtained and with 1:2 stoichiometry light blue crystals of [Ti(cp)Cl(MeCN)(4)][SbCl6](2) 2. Complete removal of chloride ion from [Ti(cp)Cl-3] requires a six-fold excess of SbCl5 when purple-blue :crystals of [Ti(cp)(MeCN)(5)][SbCl6](3) can be isolated. These products were characterised by analytical and spectroscopic (IR, H-1 NMR) data and, in the case of 3, by a crystal structure determination. Proton NMR studies indicate the presence of intermediate halide-bridged [Ti(mu-Cl)(2)Sb] species in solution during the sequential halide abstractions 1-->2-->3. Crystals of complex 3, obtained as the bis(solvate) from recrystallisation in acetonitrile, are monoclinic and X-ray structural analysis confirmed the formulation. The crystal structure [space group Cc, a = 19.650(4); b = 19.182(4), c = 12.958(3) Angstrom, beta = 91.612(3)degrees, Z = 4. R = 0.0386, R' = 0.0406] shows discrete cations and anions and a pseudo-octahedral co-ordination sphere for the Ti-IV. A significant trans influence of the cyclopentadienyl ligand affects Ti-N bond lengths in the complex