Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation with a Ni(PS)₂ Complex

Abstract

Tetra‐coordinate NiII and ZnII complexes employing the PS chelates 2‐(diphenylphosphanyl)benzenethiol (HL1) and 2‐(diisopropylphosphanyl)benzenethiol (HL2) have been synthesized and characterized by spectroscopic, structural, and electrochemical methods. All complexes were screened for electrocatalytic activity for hydrogen evolution with acetic acid and hydrochloric acid and hydrogen oxidation in the presence of triethylamine. The nickel complex Ni(L1)2 (1) was found to reduce protons from external acids to generate hydrogen with a turnover frequency of 140 s–1 at an overpotential of 1.1 V and cleave dihydrogen using redox active base triethylamine (Et3N) with a turnover frequency of 23 s–1 at an overpotential of 0.33 V. Ni(L2)2 (3) was also found to be an active catalyst for dihydrogen oxidation, but inefficient for proton reduction due to inaccessible Ni (II/I) reduction in the potential window. Zn(L1)2 (2) and Zn(L2)2 (4) complexes were found to be inadequate for their electrocatalytic behaviour towards both the reactions.

A bis(thiosemicarbazonato)‐zinc complex, an electrocatalyst for hydrogen evolution and oxidation via ligand‐assisted metal‐centered reactivity

“…With addition of varied contents of triethylamine from 0.0 to 9.00 mM, a systematic increase in the voltammetric currents emerging at 1.0 and 0.57 V versus Ag/AgNO 3 was found. These findings are consistent with a catalytic process for hydrogen oxidation, [ 16,38 ] indicating that the oxidation of [Zn‐ATSE] 2 is responsible for hydrogen oxidation. Additionally, under H 2 , the free ligand, H 2 ATSE, had an oxidation wave at 0.66 V versus Ag/AgNO 3 (Figure S24).…”

A mono-oxo-bridged binuclear iron(iii) complex with a Fe–O–Fe angle of 180.0° and its catalytic activity for hydrogen evolution

“…For example, an iron complex, [Fe(L)Cl 3 ] (L: bis(pyridin-2-ylmethyl)amine) can electrocatalyze hydrogen evolution with a TOF of 16 s −1 at −0.95 V vs. SHE, 42 a nickel complex, Ni 3 (L N2S2 ) 2 (L N2S2 : N , N ′-dimethyl- N-N ′-bis(2-mercaptoethyl)-ethylenediaminato) can provide H 2 with a TOF of 715 s −1 at −1.58 V vs. SCE, 43 an iron complex, Fe 2 ( μ -odt)(CO) 5 {Ph 2 P(CH 2 NMe 2 )} (odt: oxadithiolate) can afford H 2 with a TOF of 5.4 s −1 44 and a nickel complex, Ni(L′) 2 (HL′: 2-(diphenylphosphanyl)benzenethiol) can electro-catalyze hydrogen production with a TOF of 51 s −1 . 45…”

Recent advances in the mechanisms of the hydrogen evolution reaction by non-innocent sulfur-coordinating metal complexes

“…100 In another paper by the group of Grapperhaus, the homoleptic nickel and zinc complexes of diphenylphosphinobenzenethiolates 51 and 52 and dipropylphosphinobenzenethiolates 53 and 54 were synthesized. 165 Complex 51 reaches a TON of 3.4 over 24 h of CPE at an applied potential of −1.9 V vs. Fc + /Fc with an overpotential of 1.1 V in dichloromethane with acetic acid as a proton source, while 51-54 did not show electrocatalytic activity. The catalyst undergoes a metal centered reduction at −2.15 V vs. Fc + /Fc and kinetic studies with deuterated acid indicate the formation of a metal hydride intermediate (Scheme 23).…”