The long-sought seventeen-electron radical [(C6Me6)Cr(CO)3]+: isolation, crystal structure and substitution reaction

Abstract

A highly air-sensitive seventeen-electron half-sandwich radical, [(C₆Me₆)Cr(CO)₃]⁺, which has been long sought over 40 years, was isolated and structurally characterized. EPR spectroscopy and theoretical calculations indicate that the spin density mainly resides on the chromium atom. The radical can undergo a substitution reaction with PPh₃ to form a more stable cation, [(C₆Me₆)Cr(CO)₂(PPh₃)]⁺. This work provides a direct observation of the radical process for CO-substitution reactions found in (arene)M(CO)₃ (M = Cr, Mo, or W) systems, and suggests that other stable radicals of the type [(arene)M(CO)₃]⁺ are accessible.