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

Abstract

The reaction of a zerovalent nickel complex {Na}{(PNP)Ni(CO)} (1) with CO₂(g) results in the formation of a tetrameric cluster complex {(PN^COONaP)Ni(CO)₂}₄ (2) as the major product along with {(PNP)Ni}₂-μ-CO₃-κ²O,O (3), {(PNP)Ni}₂-μ-CO₂-κ²C,O (4) and (PNP)Ni(CO) (5). A labelling experiment with ¹³CO₂(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-μ-CO₂-κ²C,O (4) in a minor pathway. The synthesis and characterization of 2 and other products are described herein.