Electrochemical properties and C–H bond oxidation activity of [Ru(tpy)(pyalk)Cl]+ and [Ru(tpy)(pyalk)(OH)]+

Abstract

[Ru(tpy)(pyalk)Cl]Cl (pyalk = 2-(2′-pyridyl)-2-propanol) was synthesized and characterized crystallographically and electrochemically. Upon dissolution in water and acetonitrile, [Ru(tpy)(pyalk)Cl]Cl was found to form [Ru(tpy)(pyalk)Cl]⁺ and [Ru(tpy)(pyalk)(OH)]⁺, respectively. The Ru(II/III) couple of [Ru(tpy)(pyalk)Cl]⁺ was found to be relatively low compared to that of other Ru complexes in acetonitrile, but the Ru(III/IV) couple was not significantly different than other Ru complexes bearing anionic ligands. Pourbaix diagrams were generated for [Ru(tpy)(phpy)(OH₂)]⁺ (phpy = 2-phenylpyridine) and [Ru(tpy)(pyalk)(OH)]⁺ in water, and it was found that [Ru(tpy)(pyalk)(OH)]⁺ has a lower Ru(II/III) potential than [Ru(tpy)(phpy)(OH₂)]⁺ under neutral to alkaline pH. [Ru(tpy)(pyalk)(OH)]⁺ was found to catalyze C–H bond hydroxylation of secondary alkanes and epoxidation of alkenes using cerium(IV) ammonium nitrate as the primary oxidant.