Influence of an electron-deficient bridging o-carborane on the electronic properties of an [FeFe] hydrogenase active site model

Abstract

The IR carbonyl stretching frequencies of [Fe2(SRS)(CO)6] complexes correlate well with their first reduction potential; an [FeFe] hydrogenase model with a very mild reduction potential has been realized by using a strongly electron deficient carborane-dithiolate bridge.

Comparing the Reactivity of Benzenedithiolate‐ versus Alkyldithiolate‐Bridged Fe2(CO)6 Complexes with Competing Ligands

“…This effect is evidenced by the ν CO frequencies in the IR spectra of [(μ-bdt)Fe 2 (CO) 6 ] [(bdt)1, Figure 1], which can be observed at higher energies than those of [(μ-pdt)Fe 2 (CO) 6 ] [(pdt)1, Figure 1]. [26] The different electronic impact of the two bridging types is also reflected by the electrochemical behaviour of the complexes. Complex (pdt)1 is irreversibly reduced at E pc = -1.67 V vs. Fc +/0 , while (bdt)1 is reduced at around E 1/2 = -1.3 V in a reversible two-electron reaction.…”

Review of electrochemical studies of complexes containing the Fe2S2 core characteristic of [FeFe]-hydrogenases including catalysis by these complexes of the reduction of acids to form dihydrogen

“…For a review, see [97]. Also see [87] for correlation of CO frequencies with reduction potential for five complexes). It is perhaps surprising that CEP * , based as it is on the A 1 m(CO) vibrational frequency in LNi(CO) 3 , would provide reasonably linear fits for data obtained with these much different Fe 2 S 2 complexes.…”

Intramolecular hydrogen bonding interaction, a mechanism for the bridging linkages to exert electronic influence on diiron models of [FeFe]-hydrogenase

“…The variation in both steric and electronic control of the diiron centre would affect directly the electrochemical behaviours of the diiron models. Indeed, the electrochemistry of the diiron models reported in the literature differs significantly in redox potentials, electrochemical reversibility, and hence catalysis on proton reduction [7][8][9][10][11][12][13][14][15][16][17]. Although electrochemical behaviours of a molecule are affected by a number of factors, such as medium, an electrode, and thus they could not be precisely predicted by theoretical calculations, it is well known that the electrochemical behaviours are relevant to the energy levels of its frontier orbitals [18,19].…”