Tris(pyrazolyl)borate amidoborane complexes of the group 4 metals

Abstract

Treatment of the tris(pyrazolyl)borate metal triamides Tp′M(NMe₂)₃, where Tp′ = (C₃H₃N₂)₃BH (Tp) or (3,5-Me₂C₃HN₂)₃BH (Tp*) and M = Ti, Zr and Hf, with the Brønsted acidic Lewis adduct (C₆F₅)₃B·NH₃ in toluene solution leads to the formation of Tp′M(NMe₂)₂{NH₂B(C₆F₅)₃} complexes. The exception to this was the attempted preparation of Tp*Ti(NMe₂)₂{NH₂B(C₆F₅)₃} which was unsuccessful. Where Tp′ = Tp and M = Ti and Zr and where Tp′ = Tp* and M = Zr the complexes have been characterized by single crystal X-ray diffraction methods, revealing the first examples of octahedral amidoborane complexes of the group 4 metals. Attempts to drive the reactions to completion resulted in competing preferential hydrolysis of the amidoborane group, regenerating (C₆F₅)₃B·NH₃.