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Dihydrogen Complexes; gem-Hydrogenation; Metathesis; NMR Spectroscopy; Ruthenium
Abstract:
During an investigation into the fate of ruthenium precatalysts used for light-driven alkyne gem-hydrogenation reactions with formation of Grubbs-type ruthenium catalysts, it was found that the reaction of [(IPr)(η6-cymene)RuCl2] with H2 under UV-irradiation affords an anionic dinuclear σ-dihydrogen complex, which is thermally surprisingly robust. Not only are anionic σ-complexes in general exceedingly rare, but the newly formed species seems to be the first example lacking any structural attributes able to counterbalance the negative charge and, in so doing, prevent oxidative insertion of the metal centers into the ligated H2 from occurring.