Electrocatalytic CO₂ Reduction to Formate by a Highly Conjugated TriCobalt Phosphino-Thiolate Complex

Modular synthetic modification to ligand scaffolds of metal complexes provides an approach to rational improvement of existing molecular catalytic systems. A previous report from the Marinescu group has shown that a cobalt phosphino thiolate complex ([Co(triphos)(bdt)]⁺) has excellent selectivity and activity for electrocatalytic CO₂ reduction to formate. Here, a multimetallic analogue, [Co₃(triphos)₃(tht)]³⁺, that is conjugated through a trinucleating dithiolene ligand in the form of triphenylene-2,3,6,7,10,11-hexathiolate is investigated. While voltammetric studies indicate enhanced current densities under similar conditions to [Co(triphos)(bdt)]⁺, electrolysis and ultraviolet-visible spectroscopy results suggest significant catalyst degradation and overall moderate faradaic yields.