(Spectro)electrochemical and Electrocatalytic Investigation of 1,1′-Dithiolatoferrocene–Hexacarbonyldiiron

Abstract

Hexacarbonyldiiron bridged by a 1,1′dithiolatoferrocene, [Fe(C 5 H 4 S) 2 {Fe(CO) 3 } 2 ] (1), was synthesized, and the electrochemistry showed reversible oxidation at the Fe(C 5 H 4 S) 2 site and quasi-reversible reduction at the hexacarbonyldiiron site. Spectroelectrochemical techniques showed reduction-induced ligand isomerization, where the thiolate ligand went from bridging to terminal and one carbon monoxide ligand moved to a quasi-bridging position; this mechanism was further supported by cyclic voltammetry simulation and density functional theory calculations. Complex 1 showed electrocatalytic activity toward hydrogen-evolving reaction.

(Electrochemical) Properties and Computational Investigations of Ferrocenyl-substituted Fe3(μ3-PFc)2(CO)9and Co4(μ4-PFc)2(CO)9Clusters and Their Reduced Species

“…The EPR signal is a triplet with a 1:2:1 intensity ratio ascribed to two equivalent 31 P nuclei with a( 31 P) of 13.3 G. The time/potential profile of the EPR intensity allows its assignment to the first reduction step. The EPR parameters of the radical anion are very similar to those of a series of [Fe 3 (CO) 9 (PR) 2 ] − radical anions produced by chemical reduction of the corresponding Fe 3 (CO) 9 (PR) 2 clusters by cobaltocene, reported by Kochi et al, 40 or by Na/Hg. 22 Kochi et al also found that the formed [Fe 3 (CO) 9 (PR) 2 ] − species with two equivalent a( 31 P) constants slowly (within hours) converted to another type of a radical anion with a gfactor near 2.04 and nonequivalent a( 31 P) constants of 25 and 3 G. The authors suggested that the second type of species results from a μ 3 -to μ 2 -binding transition of one of the Fe−P bonds, causing a loss of equivalence between both P atoms.…”

“…This in turn supports absence of a communication through the core and the presence of a noncoupled class I system according to Robin and Day . That oxidation of ferrocenyl substituents can affect IR bands of adjacent carbonyl ligands could be shown for 1,1′-dithiolatoferrocene-hexacarbonyldiiron . Further increase of the potential results in the formation of [ 4 ] 2+ , accompanied by an equal hypsochromic shift of ∼10 cm –1 for the most intense bands.…”

“…Instead, bands at higher energy were raising, which rapidly results in a further change of the spectra (Figure 5), indicating a decomposition/reorganization of the cluster core. 39,42 This is a common phenomenon for Fe 2 (CO) 9 (PR) 2 clusters and is caused by a μ 3 /μ 2 flip of one of the P groups 38,40 and is also known for S-functionalized hexacarbonyldiiron fragments. 40 Comparison of the potential differences for the formation of [4] 2+ and [4] 2− from the respective single charged species [4] + and [4] − within the in situ measurements showed a potential range of 560 mV for the oxidation process, whereas solely 125 mV is required to convert [4] − into a further species, before the IR pattern further changes.…”

“…39 That oxidation of ferrocenyl substituents can affect IR bands of adjacent carbonyl ligands could be shown for 1,1′-dithiolatoferrocene-hexacarbonyldiiron. 40 Further increase of the potential results in the formation of [4] 2+ , accompanied by an equal hypsochromic shift of ∼10 cm −1 for the most intense bands. The IR spectra of [4] 2+ reveal a distribution of five ν(CO) stretching frequencies similar to the neutral species 4 (Figure 4).…”

Structural Variety of Iron Carbonyl Clusters Featuring Ferrocenylphosphines

“…The ferrocenyl core in both type of compounds provides unique geometric properties that cannot be achieved by condensed aromatics (Figure 1, Figure S1, Figure S2) [19,20] . Additionally, the conformational flexibility around the Cp−Fe bond of the 1,1’‐substituted sandwich allows for the synthesis of di‐ [5,7,21,22] and polymeric complexes [23] and the bending of the backbone for unique connectivity modes [24] . The 1,2‐substitution pattern (Figure 1) exhibits an increased P⋅⋅⋅P distance and a wider opening angle compared to 1,2 phenylenes, whereby a ferrocenyl annelation still occurs.…”