A subset of bimetallic active sites in biology are those that have thiolate sulfurs as bridges such as found in the [NiFe]-, [FeFe]-hydrogenases, and acetyl coA synthase. As all of these are organometallic-like in character, we are combining properties of each in attempts to develop synthetic, base metal catalysts for proton reduction and the hydrogen evolution reaction. Particular needs for the sequential addition of protons and electrons include a site for each to reside; i.e., available bases and nearby Lewis acids. Recent studies of [MN2S2.Fe(CO)(η5-C5R5)]+, (M = Ni2+, Fe(NO)2+, Co(NO)2+ and R = H or CH3), as electrocatalysts showed successive reduction and protonation steps leading to hydride-proton coupling for H2 production. DFT studies showed hemilability of the bridging cis-dithiolates as a key step to create a potential site for protonation.1 While (NO)FeN2S2, bound to {Fe(NO)2}9/10, illustrated modest electrocatalysis for proton reduction,2 replacing redox active Fe(NO)2+ with redox inaccessible NiII illustrates the role of iron dinitrosyl unit as the catalytically active center. In this study, we have synthesized [NiN2S2.Fe(NO)2]+/0 heterobimetallic complexes as electrocatalysts for proton reduction and looked for potential hydride/proton bound intermediates that reconcile the mechanism postulated by DFT studies for H2 production.

Role of redox levels in the hemilability of [NiN2S2.Fe(NO)2]+/0 complexes as electrocatalysts for proton reduction

254th National Meeting (2017)

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