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

Article abstract of DOI:10.1021/om960602k

The reaction of ammonium and iminium tetraphenylborate salts ((CH₂dCHCH₂NH₃)BPh₄, [(CH₂dCHCH₂)HNdCMe₂]BPh₄, and [(PhCH₂)HNdCMe₂]BPh₄) with transition-metal systems in a low oxidation state has been investigated. We report the oxidative addition to (Cy₃P)₂Ni(η²-CO₂) or (Cy₃P)₂NiNtNNi(PCy₃)₂ under mild conditions (253-293 K) and describe a very selective NsC or NsH bond activation. (CH₂dCHCH₂NH₃)BPh₄ or [(CH₂dCHCH₂)HNdCMe₂]BPh₄ react with (Cy₃P)₂Ni(η²-CO₂) and (Cy₃P)₂NiNtNNi(PCy₃)₂ to afford the cationic π-allyl-Ni complexes [(η³-C₃H₅)Ni(PCy₃)(NH₃)]BPh₄ (1) and [(η³-C₃H₅)-Ni(PCy₃)(η¹(N)-HNdCMe₂)]BPh₄ (2), respectively. The reaction of [(PhCH₂)HNdCMe₂]BPh₄ with (Cy₃P)₂NiNtNNi(PCy₃)₂ leads to the hydrido-imino complex [trans-(H)Ni(PCy₃)₂(η¹-(N)-PhCH₂NdCMe₂)]BPh₄ (3) through NsH bond activation. Complexes 1-3 have been fully characterized in solution by NMR (¹H,¹³C,³¹P) 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)°, involving the two P atoms from the trans PCy₃ ligands.