The reaction of [Fe₂(CO)₆(𝜇-toluene-3, 4-benzenedithiolate)] 1 and bidentate diphosphine, 1, 1′-bis(diphenylphosphino)ferrocene (dppf) has been studied. New complexes obtained have been characterized by various spectroscopic techniques as bioinspired models of the iron hydrogenase active site. The crystal structure of [Fe₂(CO)₅(𝜅¹-dppfO)(𝜇-toluene-3, 4-benzenedithiolate)] 4 is reported.

Abstract. The reaction of the tetranuclear iron complex [μ₄-Sulfido-bis{(μ-2-furylmethanethiolato) bis[tricarbonyliron](Fe—Fe)}] 1 with PPh₃ was explored. The reaction leads to the formation of the monosubstituted complex [Fe₂.μ-2-furylmethanethiolate)₂.(CO)₅.(PPh₃)] 2. X-ray crystal structure has been reported for complex 2. Complexes 1 and 2 were found to be active catalysts for proton reduction. Complexes 1 and 2 showed comparable catalytic activity for proton reduction to dihydrogen.

Supramolecular coordination complex [(Re(CO)₃)₂(dhnq)(L²)] (3) containing two fac-Re(CO)₃ cores, rigid dianionic dhnq (H2-dhnq = 6,11-dihydroxy-5,12-naphthacenedione) motif and semi-rigid ditopic nitrogen donor 1,2-bis(2-nonylbenzimidazol-1-ylmethyl)benzene (o-Nbenzbix = L²) was synthesized.Compounds o-Nbenzbix and 3 were characterized using various analytical and spectroscopic methods. The electrochemical properties of 3 were studied using cyclic voltammetric measurements. SCCs [(Re(CO)₃)₂(-dhnq)(L¹)] (1) and [(Re(CO)₃)₂(dhaq)(L¹)] (2) possessing p-xylene spacer 1,4-bis(2-nonylbenzimidazol-1-ylmethyl)benzene (L¹) and 1,4-dihydroxy-9,10-anthraquinone (H2-dhaq) were also synthesized as reported previously. SCCs 1–3 were investigated via electrochemical methods. A plot of the Randles-Sevcik equation yielded a straight line for complex 3 thus, establishing that the redox processes were diffusion-controlled.

The article primarily highlights the electrocatalytic activity towards proton reduction of macrocyclic tetranuclear iron complexes [Fe₂(l-S(CH₂)_nS-l)(CO)₆]₂ (n = 4, 1 and n = 6, 2) with both acetic acid and trifluoroacetic acid as proton sources. Further, the electrochemical results have been compared with theanalogous pentanedithiolate-bridged tetranuclear complex, [Fe₂(l-S(CH₂)₅S-l)(CO)₆]₂ A. The turnover frequency (TOF, acetic acid) for complexes 1 and 2 was found to be 5.7 h^-1 and 9.1 h^-1, respectively. An ECEC catalytic cycle (acetic acid) has been proposed for the tetranuclear iron complexes based on theexperimental data and known literature