Heteroleptic dmit nickel complexes with bis(diphenylphosphanyl)amine ligands as robust molecular electrocatalysts for hydrogen evolution

Abstract

Four new neutral heteroleptic dmit nickel complexes bearing bis(diphenylphosphanyl)amine ligands, [RN (PPh 2) 2 Ni(dmit)] (where dmit 2− = 1,-3-dithiole-2-thione-4,5-dithiolate; R = (CH 2) 4 CH 3 [1], (CH 2) 3 OCH 3 [2], (CH 2) 2 CH (CH 3) 2 [3], and CHPhCH 3 [4]), have been synthesized in moderated yields by the reactions between (n-Bu) 2 Sn(dmit) and RN (PPh 2) 2 NiCl 2 at room temperature. The complexes were fully characterized by elemental analysis, spectroscopy (Fourier transform infrared [FTIR], ultraviolet-visible [UV-vis], 1 H, 13 C{ 1 H}, and 31 P{ 1 H} nuclear magnetic resonance [NMR]), thermogravimetric analysis, and single crystal X-ray diffraction. In the crystal structures of 1-3 and 4Á2CH 2 Cl 2 , every nickel atom adopts a slightly distorted square-planar coordination by two phosphorus atoms of the RN (PPh 2) 2 ligand and two sulfur atoms of the dmit ligand. Furthermore, the electrochemical behaviors and electrocatalytic activities of 1-4 for hydrogen evolution have also been investigated by the cyclic voltammetry using trifluoroacetic acid (TFA) as the proton source. With the addition of 120-mM trifluoroacetic acid to 0.5-mM 1-4 in MeCN, the turnover frequency values of these catalysts were estimated to be 2827-5149 s −1 , and the relevant overpotentials were 0.72-0.79 V. Density functional theory (DFT) calculations and electrochemical investigations suggest that H 2 production proceeds via a key hydride intermediate [NiH (SH)] with an adjacent protonated sulfur atom of the dmit ligand in which the chelating sulfur atoms serve as proton relays. These findings demonstrate that these heteroleptic dmit nickel complexes could serve as robust and effective molecular electrocatalysts for hydrogen evolution.

Strategies for Electrochemically Sustainable H2 Production in Acid

“…[ 158 ] In addition to Co‐based complexes, molecular complexes produced by combining nickel with bis(diphenylphosphanyl)amine ligands were demonstrated to be potential homogeneous catalyst for HER, with high TOF (2827–5149 s −1 ) and stability in acidic conditions. [ 159 ] Ni molecular complexes consisting of bis(diphenylphosphanyl)amine ligands also have excellent stability but with relatively lower TOF 368.59–585.17 s –1 in trifluoroacetic acid‐containing solutions. [ 160 ] Moreover, Cu‐based [ 161 , 162 ] and metal‐free molecular complexes, e.g., 2,4,6‐triphenylpyridinium perchlorates, [ 163 ] have been developed for HER.…”

Structural versatility in nickel (II) complexes of a hydrazone ligand based on alloxan: Preparation, spectroscopic, DFT, anticancer, and molecular docking studies

“…In the processes of nerve conduction, muscle excitation, and contraction, Ni can replace Ca in the excitation process and in the binding with membrane chelating agents such as phospholipids PO 4 3− groups 24 . Moreover, nickel complexes have displayed notable antioxidant, 25 antibacterial, 26 anticancer, 27 and catalytic 28 activities.…”

Dehydrogenation of 1-Phenylethanol Catalyzed by Nickel(II)diphosphine Complexes

“…Incidentally, diphosphine nickel(II)chloride complexes attracted us due to their simple synthetic protocols, stability and well-established catalytic profile. [18][19][20][21][22][23][24][25] Here in this article, we describe the use of diphosphine nickel(II)chloride complexes in the acceptorless dehydrogenation of alcohols.…”