Borabenzene Derivatives. 26.1 Syntheses of 1-Methylboratabenzene Complexes of Titanium, Zirconium, and Hafnium. Structures of TiCl3(C5H5BMe), TiCl2Cp(C5H5BMe), ZrCl2(C5H5BMe)2, and ZrCl2Cp*(C5H5BMe)

Abstract

The complexes TiCl3(C5H5BMe) (6a), [MCl3(C5H5BMe)]x (6b, M = Zr; 6c, M = Hf), and MCl2(C5H5BMe)2 (7b, M = Zr; 7c, M = Hf) are obtained from the tetrachlorides MCl4 (M = Ti, Zr, Hf) and Li(C5H5BMe) (3), 2-(Me3Si)C5H5BMe (4), or 2-(Me3Sn)C5H5BMe (5) in excellent yields. The complexes MCl2Cp(C5H5BMe) (8a, M = Ti; 8b, M = Zr) and MCl2Cp*(C5H5BMe) (9b, M = Zr; 9c, M = Hf) are made similarly from the corresponding cyclopentadienyl precursors MCl3Cp (M = Ti, Zr) and MCl3Cp* (M = Zr, Hf). The redox potentials are shifted by 0.35−0.41 V to more anodic values than those for the corresponding Cp complexes. Molecule 6a shows a piano-stool-type structure, while 7b, 8a, and 9b possess typical bent sandwich structures.