Consecutive ligand-based PCET processes affording a doubly reduced nickel pyrazinedithiolate which transforms into a metal hydride required to evolve H₂

Abstract

Consecutive Ligand-based PCET Processes Affording a Doubly Reduced Nickel Pyrazinedithiolate which Transforms into a Metal Hydride Required to Evolve H2.

Ligand‐Based PCET Reduction in a Heteroleptic Ni(bpy)(dithiolene) Electrocatalyst Giving Rise to Higher Metal Basicity Required for Hydrogen Evolution

“…The 6‐31+G(d,p) basis set was applied to all atoms. The use of B3P86/6‐31+G(d,p) level of DFT shows good consistency with theoretical and experimental results (see Figure S22 and Table S1), as described elsewhere ,. The redox potentials were calculated by employing the experimentally determined reduction potentials of Ni II (bpy)(qdt) (Figure S23) as the benchmark (see Scheme S1 for detail) ,.…”

“…The redox potentials were calculated by employing the experimentally determined reduction potentials of Ni II (bpy)(qdt) (Figure S23) as the benchmark (see Scheme S1 for detail) ,. Moreover, the p K a DMF value of acetic acid (p K a DMF =13.5) was adopted as the benchmark to calculate the p K a values of the possible intermediates (see also Scheme S1 for detail) ,,…”

“…The use of B3P86/6-31 + G(d,p) level of DFT shows good consistency with theoretical and experimental results (see Figure S22 and Table S1), as described elsewhere. [33,[54][55][56][57] The redox potentials were calculated by employing the experimentally determined reduction potentials of Ni II (bpy)(qdt) ( Figure S23) as the benchmark (see Scheme S1 for detail). [33,[54][55][56][57][58][59][60][61][62][63] Moreover, the pK a DMF value of acetic acid (pK a DMF = 13.5) [41] was adopted as the benchmark to calculate the pK a values of the possible intermediates (see also Scheme S1 for detail).…”

“…), choice of other more stable sulfur‐donating ligands may help researchers to advance the studies on the metal‐sulfur systems. In this context, researchers attempting to explore artificial hydrogenase mimics have paid great attention to dithiolene ligands (L; examples are shown in Scheme a) in order to examine the catalytic activity of various homoleptic ML 2 ‐type complexes with M=Fe, Co, Ni, Mo, Rh, and W ,. We also reported on the electrocatalytic activity of several NiL 2 ‐type complexes, showing their unique reaction paths permitting the formation of hydride intermediates via two consecutive ligand‐based proton‐coupled electron transfer (PCET) processes (Scheme (3)) ,,…”

“…In this context, researchers attempting to explore artificial hydrogenase mimics have paid great attention to dithiolene ligands (L; examples are shown in Scheme 1a) in order to examine the catalytic activity of various homoleptic ML 2 -type complexes with M=Fe, [18][19][20] Co, [21][22][23][24] Ni, [25][26][27][28][29][30][31][32][33] Mo, [34] Rh, [35] and W. [36,37] We also reported on the electrocatalytic activity of several NiL 2 -type complexes, showing their unique reaction paths permitting the formation of hydride intermediates via two consecutive ligand-based proton-coupled electron transfer (PCET) processes (Scheme 2(3)). [30,32,33] On the other hand, our previous efforts involve mechanistic studies on the HER catalyzed by various artificial systems with different metal and ligand geometries. The platinum(II) catalysts, such as PtCl 2 (bpy) derivatives (bpy = 2,2'-bipyridine), are important examples shown to give a hydridoplatinum(III) intermediate via a metal-ligand-centered PCET pathway, [38] depicted in Scheme 2(2).…”