Reactant or reagent? Oxidation of H2 at electronically distinct nickel-thiolate sites [Ni2(μ-SR)2]+ and [Ni-SR].

The chemical bond between a Lewis-acidic metal and a Brønsted/Lewis-basic sulphur donor provides M-S structures with functional properties that are relevant for a variety of processes such as the heterolytic cleavage of H2. Direct comparison of reactivity properties between molecular M-S structures can be difficult owing to divergent electronic properties of stabilizing ligand scaffolds. This work reports on a mechanistic study of stoichiometric H2 oxidation at electronically distinct [Ni2(μ-SR)2]+ and [Ni-SR]+ structures that derive from the same 1,4-terphenyldithiophenol ligand. In this context, the effect of metal containing side-products such as [HNi(PMe3)4]+ on overall H2 oxidation reactivity displayed by Ni-S structures has been investigated quantitatively in addition to external parameters such as solvent and H2 pressure.