Self-Assembled Nickel-4 Supramolecular Squares and Assays for HER Electrocatalysts Derived Therefrom.

Solid-state structures find a self-assembled tetrameric nickel cage with carboxylate linkages, [Ni(NS'O)I(CHCN)] ([]), resulting from sulfur acetylation by sodium iodoacetate of an [NiNS] dimer in acetonitrile. Various synthetic routes to the tetramer, best described from XRD as a molecular square, were discovered to generate the hexacoordinate nickel units ligated by NS, iodide, and two carboxylate oxygens, one of which is the bridge from the adjacent nickel unit in []. Removal of the four iodides by silver ion precipitation yields an analogous species but with an additional vacant coordination site, [], a cation but with coordinated solvent molecules.

Controlling O Reactivity in Synthetic Analogues of [NiFeS]- and [NiFeSe]-Hydrogenase Active Sites.

Strategies for limiting, or reversing, the degradation of air-sensitive, base metal catalysts for the hydrogen evolution/oxidation reaction on contact with adventitious O are guided by nature's design of hydrogenase active sites. The affinity of oxygen for sulfur and selenium, in [NiFeS]- and [NiFeSe]-Hase, yields oxygenated chalcogens under aerobic conditions, and delays irreversible oxygen damage at the metals by maintaining the NiFe core structures. To identify the controlling features of S-site oxygen uptake, related (μ-E)(μ-S') (E = S or Se, = (η-CH)Fe(CO)) complexes were electronically tuned by the para-substituent on μ-EPhX (X = CF, Cl, H, OMe, NMe) and compared in aspects of communication between Ni and Fe.