The synthesis and crystallographic characterization of a complex possessing a well-defined {2Fe3S(μ-H)} core gives access to a paramagnetic bridging hydride with retention of the core geometry. Chemistry of this 35-electron species within the confines of a thin-layer FTIR spectro-electrochemistry cell provides evidence for a unprecedented super-reduced Fe^I(μ-H)Fe^I intermediate.

The synthesis and crystallographic characterization of a complex possessing a well-defined {2Fe3S(μ-H)} core gives access to a paramagnetic bridging hydride with retention of the core geometry. Chemistry of this 35-electron species within the confines of a thin-layer FTIR spectro-electrochemistry cell provides evidence for a unprecedented super-reduced Fe^I(μ-H)Fe^I intermediate.

Photoelectrocatalytic conversion of CO₂ to CO can be driven at a boron-doped, hydrogen terminated, p-type silicon electrode using a meso-tetraphenylporphyrin Fe^III chloride in the presence of CF₃CH₂OH as a proton source and 0.1 M [NBu₄][BF₄]/MeCN/5 % DMF (v/v) as the electrolyte. Under illumination with polychromatic light, the photoelectrocatalysis operates with a photovoltage of about 650 mV positive of that for the dark reaction. Carbon monoxide is produced with a current efficiency >90 % and with a high selectivity over H₂ formation. Photoelectrochemical current densities of 3 mA cm⁻² at −1.1 V versus SCE are typical, and 175 turnovers have been attained over a 6 h period. Cyclic voltammetric data are consistent with a turnover frequency of =0.24×10⁴ s⁻¹ for the photoelectrocatalysis at p-type Si at −1.2 V versus SCE this compares with =1.03×10⁴ s⁻¹ for the electrocatalysis in the dark on vitreous carbon at a potential of −1.85 V versus SCE.

We show that a robust molybdenum hydride system can sustain photoelectrocatalysis of a hydrogen evolution reaction at boron-doped, hydrogen-terminated, p-type silicon. The photovoltage for the system is about 600–650 mV and the current densities, which can be sustained at the photocathode in non-catalytic and catalytic regimes, are similar to those at a photoinert vitreous carbon electrode. The kinetics of electrocatalysed hydrogen evolution at the photocathode are also very similar to those measured at vitreous carbon—evidently visible light does not significantly perturb the catalytic mechanism. Importantly, we show that the doped (1–10 Ω cm) p-type Si can function perfectly well in the dark as an ohmic conductor and this has allowed direct comparison of the cyclic voltammetric behaviour of the response of the system under dark and illuminated conditions at the same electrode. The p-type Si we have employed optimally harvests light energy in the 600–700 nm region and with 37 mW cm⁻² illumination in this range; the light to electrochemical energy conversion is estimated to be 2.8 %. The current yield of hydrogen under broad tungsten halide lamp illumination at 90 mW cm⁻² is (91±5) % with a corresponding chemical yield of (98±5) %.

Selective electrocatalytic oxidation of hydrocarbons to alcohols, epoxides or other (higher value) oxygenates should in principal present a useful complementary anodic half-cell reaction to cathodic generation of fuels from water or CO₂ viz. an alternative to oxygen evolution. A series of new basket-handle thiolate Fe^III porphyrins have been synthesised and shown to mediate anodic oxidation of hydrocarbons, specifically adamantane hydroxylation and cyclooctene epoxidation. We compare yields obtained by electrochemical and chemical oxidation of the thiolate porphyrins and benchmark their behaviour against that of Fe^III tetraphenyl porphyrin chloride and its tetrapentafluorophenyl analogue.

The model [FeFe]-hydrogenase subsite Fe₂(μ-odt)(CO)₄(PMe₃)₂ (odt = 2-oxapropane-1,3-dithiolate) has been crystallized for the first time, revealing an apical–basal arrangement of the two phosphane groups. Protonation of this species has been studied by a combination of stopped-flow ultraviolet and infrared techniques along with time-resolved NMR spectroscopy. The kinetics of the protonation are similar to those for Fe₂(μ-edt)(CO)₄(PMe₃)₂ (edt = ethane-1,2-dithiolate) and are much slower than those for the protonation of Fe₂(μ-pdt)(CO)₄(PMe₃)₂ (pdt = propane-1,3-dithiolate). The dithiolate bridge length is therefore not the key determinant of reactivity in these simple model systems.