Oxidative addition of ammonium and iminium tetraphenylborates to low-valent metal complexes. Evidence of selective N-C and N-H activation. A new, easy route to cationic allyl- and hydridonickel complexes

The reaction of ammonium and iminium tetraphenylborate salts ((CH2=CHCH2NH3)BPh(4), [(CH2=CHCH2)HN=CMe(2)]BPh(4), and [(PhCH(2))HN=CMe(2)]BPh(4)) with transition-metal systems in a low oxidation state has been investigated. We report the oxidative addition to (Cy(3)P)(2)Ni(eta(2)-CO2) or (Cy(3)P)(2)Ni=NNi(PCy(3))(2) under mild conditions (253-293 K) and describe a very selective N-C or N-H bond activation. (CH2=CHCH2NH3)BPh(4) or [(CH2=CHCH2)HN=CMe(2)]BPh(4) react with (Cy(3)P)(2)Ni(eta(2)-CO2) and (Cy(3)P)(2)NiN=NNi(PCy(3))(2) to afford the cationic pi-allyl-Ni complexes [(eta(3)-C3H5)Ni(PCy(3))(NH3)]BPh(4) (1) and [(eta(3)-C3H5)Ni(PCy(3))(eta(1)(N)-HN=CMe(2))]BPh(4) (2), respectively. The reaction of [(PhCH(2))HN=CMe(2)]BPh(4) with (Cy(3)P)(2)Ni=NNi(PCy(3))(2) leads to the hydride-imino complex [trans-(H)Ni(PCy(3))(2)(eta(1)(N)-PhCH(2)N=CMe(2))]BPh(4) (3) through N-H bond activation. Complexes 1-3 have been fully characterized in solution by NMR (H-1, C-13, P-31) spectroscopy The hydrido-imino complex 3, characterized in the solid state by a X-ray diffraction study, shows a distorted-square-planar coordination around the nickel atom with a very narrow P-Ni-P angle, 148.6(2)degrees, involving the two P atoms from the traits PCy(3) ligands.