A mononuclear iron carbonyl complex [Fe(μ-bdt)(CO)₂(PTA)₂] with bulky phosphine ligands: a model for the [FeFe] hydrogenase enzyme active site with an inverted redox potential

Abstract

A mononuclear hexa-coordinated iron carbonyl complex [Fe(μ-bdt)(CO)(PTA)] 1 (bdt = 1,2-benzenedithiolate; PTA = 1,3,5-triaza-7-phosphaadamantane) with two bulky phosphine ligands in the trans position was synthesized and characterized by X-ray structural analysis coulometry data, FTIR, electrochemistry and electronic structure calculations. The complex undergoes a facilitated two-electron reduction 1/1 and shows an inverted one-electron reduction for 1/1 at higher potentials. Electrochemical investigations of 1 are compared to the closely related [Fe(bdt)(CO)(PMe)] compound. A mechanistic suggestion for the hydrogen evolution reaction upon proton reduction from acid media is derived. The stability of 1 in both weak and strong acids is monitored by cyclic voltammetry.

Carbon monoxide substitutions by trimethyl phosphite in diiron dithiolate complex: Fe-Fe bond cleavage, selectivity of the substitutions, crystal structures and electrochemical studies

“…The carbon monoxide substitution by a ligand L more donor than (CO) has been largely investigated in iron polynuclear complexes [16][17][18][19][20][21][22][23][24][25][26][27]. Binuclear compounds (µ-η 2 -ROCS)(µ-SMe)Fe 2 (CO) 6 [16] and [(µ-RS) 2 Fe 2 (CO) ] [25] reacted with P(OMe) 3 under ETC activation to afford monosubstituted compounds firstly and then the disubstituted products [17,18,28].…”

Mechanism of Diiron Hydrogenase Complexes Controlled by Nature of Bridging Dithiolate Ligand

“…To validate the minimum energy structure as well as to calculate thermodynamic properties, we have performed the frequencies calculation on the gas‐phase‐optimized structures at the same level of theory. Redox potentials were calculated following the references[ 80 , 81 ] and the redox potential of all complexes is reported relative to Fc/Fc + reference electrode in acetonitrile.…”

A five-coordinate cobalt bis(dithiolene)–phosphine complex [Co(pdt)2(PTA)] (pdt = phenyldithiolene; PTA = 1,3,5-triaza-7-phosphaadamantane)

“…Electronically, the PTA ligand is much less electron donating than PMe 3 , while a slightly better electron donor than PPh 3 (Darensbourg et al, 1999). However, the formation of heteroleptic dithiolene-phosphine complexes from the corresponding homoleptic metal-dithiolene has not been fully explored (Natarajan et al, 2017). Reactions of homoleptic metal-dithiolenes with phosphines to produce heteroleptic complexes have exhibited interesting metal-ligand redox interplay as a result of the redox-active or non-innocent nature of dithiolene ligands (Chandrasekaran et al, 2014).…”