Kinetic isotope effect offers selectivity in CO 2 reduction.

A binuclear Ni complex with N,O donors catalyzes CO 2 reduction via its Ni(I) state. The product distribution when H 2 O is used as a proton source shows similar yields for CO, HCOOH and H 2 . However, when D 2 O is used, the product distribution shows a ∼65% selectivity for HCOOH. In situ FTIR indicates that the reaction involves a Ni-COO* and a Ni-CO intermediate. Differences in H/D KIEs on different protonation pathways determine the selectivity of CO 2 reduction.