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

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.