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 CO 2, allowing us to address a long-standing question related to Ni-catalyzed carboxylation reactions.