Synthesis, characterization, and crystal structure of [Cu{(3,5-Ph2Pz)2BH2}2]0: Evidence of a B–H–Cu agostic interaction

The synthesis of the air stable copper(II) complex of the dihydrobis(3,5-diphenyl pyrazolyl) borate ligand, [Cu{(3,5-Ph2Pz)2BH2}2]0, is reported. This copper complex has been synthesized by reacting [(3,5-Ph2Pz)2BH2]K with Cu(CH3COO)2 in CH2Cl2. [Cu{(3,5-Ph2Pz)2BH2}2]0 crystallizes as brown triclinic(P 1 ¯ (No. 2)) crystals. X-ray crystallography and FTIR spectroscopy reveal that the copper atom is in a pseudooctahedral environment comprised of a square plane formed by the nitrogen atoms of the pyrazole rings, while one of the hydrogens from each boron sits in a pseudo axial position. [Cu{(3,5-Ph2Pz)2BH2}2]0 exhibits the shortest Cu…H–B distance (2.508 Å) in comparison to similar, previously reported analogs. A DFT analysis of these complexes reveals that there is a weak stabilizing agostic interaction between copper and the hydride in the boron atom, which is induced by steric effects stimulated by the presence of the bulky phenyl substituents in the pyrazole rings.