Preparation and Reactions of Base-Free Bis(1,3-di-tert-butylcyclopentadienyl)titanium, Cp′2Ti, 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 −2 J = 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 (μ-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 (μ-O) 2 .