On the role of hydrogen bond acceptors in electrocatalytic hydride formation

This is the authors' abstract. We don't add key points for this paper.

Carefully designed mechanistic studies often provide the most important insights for future advances in catalysis. Here, we study the role of hydrogen-bond (H-bond)-accepting functional groups in a catalyst microenvironment. This approach provides quantitative information on the rate of electrochemically driven catalyst-hydride formation from protons. Ligand substitution of Na(diglyme) 2 [Fe 4 N(CO) 12 ] was used to access a series of six clusters with various H-bond-accepting secondary coordination sphere (SCS) functional groups that were chosen to span a wide range of H-bond-acceptor strengths ( B ). We demonstrate that the rate of formation of [H-Fe 4 N(CO) 12 ] − increases linearly with B , because the H-bond acceptor modulates the reactivity of water that serves as a proton source for the formation of [H-Fe 4 N(CO) 12 ] − . Specifically, the substrate water likely accumulates near the catalyst active site and/or has lower p K a when the SCS functional groups are stronger H-bond acceptors. The rate of [H-Fe 4 N(CO) 12 ] − formation is not correlated directly with p K a of the SCS H-bond-accepting functional group.