Structurally Well-Defined PC(sp³)P Osmium Pincer Catalysts for Methylation of Alcohols, Indoles, Phenols, and Sulfonamides Using Methanol as a C₁ Source

Recent findings show pincer catalysts of osmium superior in a broad spectrum of synthetically valuable transformations. This article reports structurally well-defined Os(II)(PCspP)-P-3 complexes stabilized by a functional dibenzobarrelene-based pincer ligand. We describe their organometallic and catalytic properties in the hydride transfer reactions. We demonstrate that the osmium center, covalently locked within the 3-dimensional ligand pocket, exhibits strictly predictable coordination behavior and redox rigidity while remaining catalytically active owing to the potential cooperation with a proximate functional side arm. The described Os(II)(PCspP)-P-3 complexes were found as superior catalysts in the mild and selective methylation of alcohols, indoles, phenols, and sulfonamides using methanol as a C-1 source.