Formation of N2O from a Nickel Nitrosyl: Isolation of the cis-[N2O2]2– Intermediate

Addition of 2,2′-bipyridine (bipy) to [Ni(NO)(bipy)][PF6] (1) results in formation of a rare five-coordinate nickel nitrosyl [Ni(NO)(bipy)2][PF6] (2). This complex exhibits a bent NO– ligand in the solid state. On standing in acetonitrile, 2 furnishes the NO coupled product, [Ni(κ2-O2N2)(bipy)] (8) in moderate yield. Subsequent addition of 2 equiv of acetylacetone (H(acac)) to 8 results in formation of [Ni(acac)2(bipy)], N2O, and H2O. Preliminary mechanistic studies suggest that the N–N bond is formed via a bimetallic coupling reaction of two NO– ligands.