Construction of a low-valent thiolate-bridged dicobalt platform and its reactivity toward hydrogen activation and evolution

Abstract

Low-valence transition metallic complexes have drawn longstanding attention due to their high reactivity toward catalytic transformation of various small molecules. Among these known complexes, the low-valence metal centres are commonly stabilized by neutral bulky ligands with strong electron-donating capacity. However, low-valence bimetallic complexes supported by anionic sulfur and cyclopentadienyl ligands are still difficult to obtain in high isolated yield. Herein, we report the synthesis and characterization of two scarce thiolate-bridged CoICoII and CoICoI complexes bearing sterically demanding ligands through two stepwise one-electron reduction processes. Interestingly, the CoICoII complex can facilely promote the homolytic cleavage of dihydrogen across the short Co−Co metallic bond to give a CoIICoIII dihydride bridged complex, which is capable of serving as a competent hydrogen atom transfer agent. Moreover, the anionic CoICoI complex can trigger a stepwise hydrogen generation cycle involving several isolated and structurally well-characterized intermediates.