Nickel(I)-mediated transformations of carbon dioxide in closed synthetic cycles: reductive cleavage and coupling of CO2 generating Ni(I)CO, Ni(II)CO3 and Ni(II)C2O4Ni(II) entities.

The β-diketiminato nickel(I) complex K2[L(tBu)Ni(I)(N2(2-))Ni(I)L(tBu)] reacts with CO2 via reductive disproportionation to form CO and CO3(2-) containing products, whereas after employment of the Ni(I) precursor [L(tBu)Ni(I)(N2)Ni(I)L(tBu)] reductive coupling of CO2 was observed giving an oxalate bridged dinickel(II) complex. The addition of KC8 to the carbonate and oxalate compounds formed leads to the regeneration of the initial Ni(I) complexes in an N2 atmosphere, thus closing synthetic cycles.