Formation of a tetranickel octacarbonyl cluster from the CO2 reaction of a zero-valent nickel monocarbonyl species

The reaction of a zerovalent nickel complex {Na}{(PNP)Ni(CO)} (1) with CO2(g) results in the formation of a tetrameric cluster complex {((PNP)-P-COONa)Ni(CO)(2)}(4) (2) as the major product along with {(PNP)Ni}(2)-mu CO3-kappa O-2,O (3), {(PNP)Ni}(2)-mu-CO2-kappa C-2,O (4) and (PNP)Ni(CO) (5). A labelling experiment with (CO2)-C-13(g) reveals that not only the carbamate moeity but also the CO ligand in 2 originate from CO2(g). The formation of both a carbonyl species 2 and a carbonate species 3 indicates that nickel-mediated reductive disproportionation of CO2 occurs. Alternatively, a direct CO2 oxidative reaction of 1 occurs to produce {(PNP)Ni}(2)-mu-CO2-kappa C-2,O (4) in a minor pathway. The synthesis and characterization of 2 and other products are described herein.