Five new heteroleptic nickel complexes containing O‐methyldithiophosphate and aminodiphosphine monosulfide ligands, [Ni((PPh2)({S}PPh2)NR)(S2P{O}OCH3)] (R = (CH2)4CH3 (1), (CH2)3OCH3 (2), (CH2)3SCH3 (3), (CH2)2CH(CH3)2 (4), and C6H4CH3–4 (5)), were synthesized by two different methods at room temperature. All complexes were characterized by elemental analysis, spectroscopy (1H, 13C, 31P nuclear magnetic resonance [NMR], and ultraviolet–visible [UV–vis]), single crystal X‐ray diffraction as well as thermogravimetric analysis. In the crystal structures of 1–4 and 5⋅CH2Cl2, the nickel atom locates in a slightly distorted square‐planar coordination by one phosphorous atom and three sulfur atoms from the aminodiphosphine monodulfide and O‐meyldithiophosphate ligands. Furthermore, their electrochemical behaviors and electrocatalytic performances for the reduction proton to hydrogen have also been evaluated by the cyclic voltammetry using trifluoroacetic acid (TFA) as the proton source. With the addition of 120 mM TFA to MeCN solution of 1–5 (1.0 mM), the turnover frequencies are estimated to be 494–706 s−1, and the corresponding overpotentials are 0.61–0.70 V versus Fc+/Fc, respectively. This finding diagnoses that the heteroleptic nickel complexes can serve as robust and effective molecular electrocatalysts for hydrogen evolution.

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