The insertion reaction of acetonitrile on aryl nickel complexes stabilized by bidentate N,N′-chelating ligands

Abstract

Organometallic complexes to be used as single component precursors in the catalytic dimerization/polymerization of olefins usually must contain a labile ligand that can easily be displaced by the olefin. This is the first step in the activation of the precursor. One commonly used labile ligand is a nitrile. Here we report an example of incompatibility between the nickel or palladium aryl bond and acetonitrile. Neutral [MBr(Mes)NN] complexes in which Mes = 2,4,6-Me₃C₆H₂, NN = diazabutadiene (DAD), pyridinylimine (PIM), 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) gave the expected [M(Mes)(3,5-lut)(NN)][BF₄] compounds and the unexpected [Ni(Mes){NHC(Me)(2,4,6-Me₃C₆H₂)}(NN)][BF₄] complexes in the presence of TlBF₄ and 3,5-lutidine or acetonitrile. The sequence of reactions that leads to the imine ligand must include an initial insertion of the nitrile on the σ(Ni–Mes) bond. These ionic complexes remain stable under 20 bar of ethylene.