Ligand-Based Reactivity of Oxygenation and Alkylation in Cobalt Complexes Binding with (Thiolato)phosphine Derivatives

Reduction induced S-nucleophilicity in mono-dithiolene molybdenum complexes - in situ generation of sulfonium ligands

The reduction of a molybdenum monodithiolene complex, [Mo(CO)₂(dt)(dppe)], in the presence of dichloromethane leads to the transfer of CH₂ to sulfur and respective sulfonium species. Detailed analytical and mechanistical spectroscopic and electrochemical studies reveal the reasons for the unexpected formation and composition of the very unusual resultant complexes to be electronic-energetic in nature.

Electrocatalytic syngas generation with a redox non-innocent cobalt 2-phosphinobenzenethiolate complex

A cobalt complex supported by the 2-(diisopropylphosphaneyl)benzenethiol ligand was synthesized and its electronic structure and reactivity were explored. X-ray diffraction studies indicate a square planar geometry around the cobalt center with a trans arrangement of the phosphine ligands. Density functional theory calculations and electronic spectroscopy measurements suggest a mixed metal-ligand orbital character, in analogy to previously studied dithiolene and diselenolene systems. Electrochemical studies in the presence of 1 atm of CO₂ and Brønsted acid additives indicate that the cobalt complex generates syngas, a mixture of H₂ and CO, with faradaic efficiencies up to >99%. The ratios of H₂ : CO generated vary based on the additive. A H₂ : CO ratio of ∼3 : 1 is generated when H₂O is used as the Brønsted acid additive. Chemical reduction of the complex indicates a distortion towards a tetrahedral geometry, which is rationalized with DFT predictions as attributable to the populations of orbitals with σ*(Co-S) character. A mechanistic scheme is proposed whereby competitive binding between a proton and CO₂ dictates selectivity. This study provides insight into the development of a catalytic system incorporating non-innocent ligands with pendant base moieties for electrochemical syngas production.