Trinuclear clusters containing 2-aminopyridinate/pyrimidinate ligands as electrocatalysts for proton reduction

Publication date: 15 November 2017 Source:Journal of Organometallic Chemistry, Volume 851 Author(s): Shishir Ghosh, Graeme Hogarth Triiron and triruthenium clusters containing capping 2-aminopyridinate/pyrimidinate ligands are developed as functional models of the [FeFe]-hydrogenase for electrocatalytic reduction of protons to hydrogen. The 48-electron clusters Fe3(CO)9(μ3-pyNH)(μ-H) (1), Fe3(CO)9(μ3-pymNH)(μ-H) (2), Ru3(CO)9(μ3-pyNH)(μ-H) (3) and Ru3(CO)9(μ3-pymNH)(μ-H) (4) (pyNH = 2-aminopyridinate, pymNH = 2-aminopyrimidinate) are prepared from reactions of M3(CO)12 (M = Fe or Ru) with the corresponding heterocyclic amine at elevated temperatures. Each contains a hydride and a residual amino hydrogen in close proximity (ca. 2.8 Å). The triiron 2-aminopyridinate cluster 1 does not protonate by TsOH·H2O (used as the proton source during catalysis), whereas its ruthenium analogue 3 undergoes slow protonation across a ruthenium-ruthenium bond. The 2-aminopyrimidinate clusters 2 and 4 undergo rapid protonation at the ring nitrogen. In MeCN, the triiron clusters show a single irreversible reduction wave (E p = −1.61 V for 1; E p = −1.47 V for 2) in the cathodic region of their CVs, while the triruthenium clusters display a pair of irreversible cathodic waves (E p = −2.01 and −2.15 V for 1; E p = −1.93 and −2.09 V for 2). All catalyze proton reduction in the presence of TsOH·H2O but different mechanisms are proposed. The triiron clust...

Source: Journal of Organometallic Chemistry - October 22, 2017 Category: Chemistry Source Type: research