Structural and electrochemical investigations of new mononuclear nickel(II) dithiolate complexes bearing a pendant amine

To further develop the biomimetic chemistry of [FeFe]- and [NiFe]-hydrogenases for the catalytic reduction of protons to hydrogen (H-2), two new mononuclear Ni(II) ethanedithiolate complexes [{(Ph2PCH2)(2)NR}Ni(SCH2CH2S)] (R = tert-butyl (Bu-t), 1 and n-butyl (Bu-n), 2) with pendant amine-containing diphosphines were synthesized in moderate yields from the treatments of mononickel dichlorides [{(Ph2PCH2)(2)NR}NiCl2] with ethanedithiol (HSCH2CH2SH) with triethylamine (Et3N) as an acid-binding agent at room temperature. The as-prepared complexes 1 and 2 have been fully characterized by means of elemental analysis, nuclear magnetic resonance (NMR) spectrum, and X-ray crystallography. Further, the electrochemical properties of 1 and 2 are investigated in the absence or presence of acetic acid (HOAc) by using cyclic voltammetry (CV), suggesting that they can be considered as the active electrocatalysts for proton reduction to H-2.