KCS

The reactivity of transition metal nitrosyl complexes is of particular interest in our research. This is due in part to the extensive roles of nitric oxide (NO) in biology, which involves an integral part of immune response, vasodilatation, and neurotransmission. Recent researches have revealed that reactive nitrogen species (RNS) might be generated from the interaction of NO with various reactive oxygen species (ROS) mediated by transition metal ions in biological systems. Our investigation has focused on the chemistry of metal nitrosyl in particular with nickel. To date, structurally characterized nickel nitrosyl complexes reported in literature feature only an Enemark-Feltham configuration of {Ni(NO)}¹⁰. Despite this lack of diversity, recent works have shown that nickel nitrosyl complexes can exhibit a diverse range of reactivity such as dissociation, disproportionation, and reduction. Recently we have synthesized dinuclear nickel dinitrogen complexes {(PP^RP)Ni}₂(?-N₂) with tridentate PP^RP ligands; PP^RP = P(R)(2-PiPr₂-C₆H₄)₂, (R = Ph and Me), well-characterized by various physical methods such as NMR and IR spectroscopies as well as X-ray crystallography. A series of 4-coordinate nickel nitrosyl complexes [(PP^RP)Ni(NO)][BF₄] were prepared by the reaction of dinuclear nickel N₂ complexes with nitrosonium ion (NOBF₄). A neutral paramagnetic nickel nitrosyl species (PP^RP)Ni(NO) featuring an unusual {Ni(NO)}¹¹ configuration was chemically prepared by the chemical reduction of [(PP^RP)Ni(NO)][BF₄]. As closely analogous complexes, square planar 4-coordinate nickel nitrosyl complexes (PNP)Ni(NO) with a tridentate PNP^- ligand; (PNP^- = N[2-P iPr₂-4-Me-C₆H₃]₂^-) was also prepared by oxygen atom transfer reaction. A series of these nickel nitrosyl complexes were characterized by various spectroscopic techniques. Details of nickel nitrosyl species will be presented especially describing their structural parameters and electronic character.