Preparation and reactions of base-free bis(1,3-di-tert-butylcyclopentadienyl)titanium, Cp′2 Ti, and related compounds

The titanium(III) metallocene derivatives [1,3-(Me(3)C)(2)C(5)H(3)](2)TiX, Cp '(2)TiX, X = Cl, Me, H, OH, are prepared and shown to be monomeric with a d(1) electron configuration by solid state magnetic susceptibility studies over the temperature range 5-300 K. Reduction of the chloride by potassium amalgam in an argon atmosphere yields the base-free titanocene Cp '(2)Ti, which is a spin triplet over the temperature range 5-300 K. In contrast, reduction in a nitrogen atmosphere gives the dimetal metallocene Cp '(2)Ti(N(2))TiCp '(2), which shows a singlet-triplet equilibrium over the temperature range 5-300 K, which can be modeled by Heisenberg coupling with -2J = 210 cm(-1). The base-free titanocene reacts reversibly with H(2) or C(2)H(4) to give Cp '(2)TiH(2) and CP '(2)Ti(C(2)H(4)), respectively. Both adducts are characterized by X-ray crystallography. The base-free titanocene reacts irreversibly with PhC CPh or N(2)O to give Cp '(2)Ti(PhC CPh) and Cp '(4)Ti(2)(mu-O), which are characterized by X-ray crystallography. In contrast Cp '(2)Ti(C(2)H(4)) reacts with N(2)O to give the bisoxo-bridged dimetal derivative Cp '(4)Ti(2)(mu-O)(2).