Neutral heteroleptic nickel complexes incorporating maleonitriledithiolate and bis(diphenylphosphanyl)amine as robust molecular electrocatalysts for hydrogen evolution

Electrocatalytic Hydrogen Evolution Catalyzed by 3,4‐Toluenedithiolate Nickel Complexes of Bis(diphenylphosphine)amine Ligand Containing An Azahydrophilic Group

“…The FTIR spectra of 1 and 2 show the PÀ NÀ P stretching bands of the bis(diphenylphosphine)amine ligand at 842 and 861 cm À 1 and the CÀ S stretching bands for the tdt ligand at 1103 and 1102 cm À 1 , respectively. [19,23,25] In the 1 H NMR spectrum of 1, one multiplet at 7.90-7.99 ppm and two triplets at 7.72 and 7.65 ppm are assigned to the phenyl protons of the PPh 2 moieties. The proton signals of the tdt ligand for 1 appear two doublets at 7.05 and 7.00 ppm and one double doublet at 6.54 ppm, respectively.…”

“…[20,21] Meanwhile, Xie and co-workers reported that dcpf-supported nickel complexes containing O-alkyldithiophosphate ligands, [(dcpf)Ni(S 2 P{O}OR)] (dcpf = 1,1-bis (dicyclohexylphosphino)ferrocene), present higher electrocatalytic performances for the reduction trifluoroacetic acid (TFA) to hydrogen with turnover frequencies of 1047-2545 s À 1 . [22] In addition, bis(diphenylphosphine)amine (RN(PPh 2 ) 2 , PNP) has also been used in the fabrication of complex electrocatalysts for hydrogen evolution, such as [(RN(PPh 2 ) 2 )Ni(S 2 P{O}OR')], [18] [Fe 2 (μpdt)(CO) 4 {(μ-Ph 2 P) 2 NR], [19] [(RN(PPh 2 ) 2 )Ni(mnt)], [23] and [(RN-(PPh 2 ) 2 )Ni(bdt)] [24,25] (pdt = propylene-1,3-dithiolate, mnt = maleonitriledithiolate, and bdt = 1,2-benzenedithiolate).…”

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

“…[32,35,76,77] The irreversible oxidation peak at E pa = 0.22 V versus Fc + /Fc can be assigned to the oxidation of N-butyl bis(diphenylphosphanyl)amine ligand. [78] Similarly, 2-4 also show one reversible reduction peak for Ni II /Ni I couple at E pc = −1.58, −1.58, and −1.66 V versus Fc + /Fc and the irreversible oxidation event at E pa = 0.22-0.24 V versus Fc + /Fc for bis(diphenyl-phosphanyl)amine ligands, respectively (see Figures S21, S27, and S33).…”

“…[57] ; while the study on [RN (PPh 2 ) 2 Ni(mnt)] by Mou et al revealed that the neutral nickel species is reduced to the monoanion, followed by the protonation on the nickel atom. [78] Thirdly, a (Figure 12) reveals only 7% contribution of S1 and S2 atoms, 27% contribution from P1 and P2 atoms, and 52% contribution from Ni atom. This is different from [n-Bu 4 N][Ni (mnt) 2 ], where the diprotonations occur on two sulfur atoms from two different mnt ligands and yields a [Ni (mntH)(mntH)] − species.…”

“…Under the identical conditions, the TOF values of 1-4 for hydrogen production are 8-14 times than those of analogous nickel complexes [RN (PPh 2 ) 2 Ni(mnt)], and the corresponding overpotentials are slightly greater than those of [RN (PPh 2 ) 2 Ni(mnt)]. [78] The difference in catalytic activity for hydrogen evolution is mainly caused by the significant electronic difference between the dithiolene ligands, namely, that dmit ligand is an electronic donor while mnt ligand is an acceptor. The secondary reason may come from the slightly difference for electrocatalytic hydrogen production mechanism, which is described below.…”