A Nickel(II)–Sulfur‐Based Radical‐Ligand Complex as a Functional Model of Hydrogenase

Abstract

Better than nature! A nickel(II) dithiolene complex [NiII(L2−)(L−.)][PPh4] (1; see figure; L=1,2‐dicarbomethoxyethylene dithiolate) electrocatalyzes hydrogen evolution at the lowest achievable reduction potential (${{{\rm E}{{{\rm {\rm red}}\hfill \atop {\rm {\rm p}}\hfill}}}}$, −0.69 V) in CH3CN and also in aqueous medium (${{{\rm E}{{{\rm {\rm red}}\hfill \atop {\rm {\rm p}}\hfill}}}}$, −0.71 V) to date. Compound 1 shows strikingly similar EPR and reduction potential values to those observed with native Ni‐containing hydrogenases.

Bioinspired Tungsten Dithiolene Catalysts for Hydrogen Evolution: A Combined Electrochemical, Photochemical, and Computational Study

“…7 As a consequence a wealth of mono and poly-nuclear Ni and Fe complexes have been studied for their proton reduction catalytic performances in electro-and photo-chemical systems. 1,[8][9][10][11] There are other biological active sites which might deserve more attention. Indeed Nature has also selected molybdenum and tungsten to catalyze complex redox reactions such as in formate dehydrogenase or carbon monoxide dehydrogenase, enzymes which allow interconversion of CO 2 with formate and carbon monoxide, respectively.…”

A Bioinspired Nickel(bis-dithiolene) Complex as a Homogeneous Catalyst for Carbon Dioxide Electroreduction

“…, synthesized according to a previously published procedure, 28 was studied and compared to complex 2b. As it can be seen in Figure S10, no catalytic activity was found.…”

Comment on “A Nickel(II)‐Based Radical‐Ligand Complex as a Functional Model of Hydrogenase”

“…Begum and co‐workers present a combination of X‐ray structure analysis, EPR and UV/Vis spectroscopy, cyclic voltammetry, and DFT calculations to elucidate the electronic structure and proton reduction of the biomimetic complex 1 , [Ni(L 2 )] − , in which L= cis ‐1,2‐dicarbomethoxyethylene dithiolate (Scheme ) 2. They come to the conclusion, that in complex 1 and in the Ni‐C state of [NiFe] hydrogenase a Ni II ‐based radical ligand exists.…”

“… Chemical structures of monanionic nickel bisthiolene complexes: complex 1 in which R= cis ‐1,2‐dicarbomethoxyethylene dithiolate,2 complex 2 where R=CN is taken for comparison, see reference 3. …”

“…use the shortening of the CS bonds from 1.74 Å in the dianonic [Ni(L 2− ) 2 ] 2− to 1.73 and 1.72 Å in the monanionic [Ni(L 2− ) 2 ] − as an indication of ligand oxidation to form a radical and formulate their complex as a [Ni II (L 2− )(L −. )] − 2. This formulation can easily be misinterpreted because it implies that the unpaired electron spin of the S =1/2 state is localized on one of the ligands and that the ground state is a mere ligand‐based radical.…”