New nickel–carbon dioxide complex: synthesis, properties, and crystallographic characterization of (carbon dioxide)-bis(tricyclohexylphosphine)nickel

[Ni(CO2)(PCy3)2],0·75(C7H8), where Cy = cyclohexyl, can be made either by treating [Ni(PCy3)3] or [{Ni(PCy3)2}2N2] with CO2 in toluene, or by direct reduction of [NiBr2(PCy3)2] with sodium sand under CO2; the complex is planar, the CO2 ligand possesses bent geometry and is co-ordinated through the carbon atom and one of the oxygen atoms.