Electrocatalytic H 2 Evolution of Bis(3,5-di-methylpyrazol-1-yl)acetate Anchored Hexa-coordinated Co(II) Derivative

A mononuclear Co(II) derivative, (1) is afforded by employing a ‘scorpionate’ type precursor, bdtbpza [bdtbpza = bis(3,5-di-t-butylpyrazol-1-yl)acetate]. Single crystal X-ray structure reveals that the Co II ion exhibits an octahedral geometry possessing on a O 6 coordination environment. Detailed EPR interpretation and electrocatalytic hydrogen evolution study are reported. Electrochemical and catalytic study of 1 in DMSO with the presence of acetic acid as weak proton source shows an observed rate constant of 3.7 × 10 3  s −1 and hydrogen evolution Faradaic efficiency of 74.7%. The catalytic process requires two-electron reduction of the catalyst and formation of a cobalt(II)-hydride species as reactive intermediate.