B–N Cleavage in (9‐BBN)bis(pyrazolyl)borate NiII Complexes

Three kinds of Ni-II complexes, the singly hydroxo-bridged complex 2, doubly hydroxo-bridged complexes 3a and 3b, and dinuclear Ni complex 4, were readily prepared from reactions of the salt K[(BBN)Bp (R)] {(BBN)Bp (R) = (9-BBN)bis(pyrazolyl)borate} and the NiCl2(PPh3)(2) precursor via B-N bond cleavage process in dichloromethane or toluene. Complex 2 is a rare example of partial hydrolysis of the coordinated pyrazolylborate ligand, while complexes 3a and 3b demonstrate the unreported new form that complete hydrolyses of the coordinated pyrazolylborate ligand produced. Different mechanisms for the formation of complexes 2-4 are proposed.