Although the catalytic carboxylation of unactivated alkyl electrophiles has reached remarkable levels of sophistication, the intermediacy of (phenanthroline)Ni(I)-alkyl species – complexes proposed in numerous Ni-catalyzed reductive cross-coupling reactions – has been subject to speculation. Herein, we report the synthesis of such elusive (phenanthroline)Ni(I) species and their reactivity with CO2, allowing us to address a long-standing challenge related to metal-catalyzed carboxylation reactions.