Structure and Reactivity of Nonporphyrinic Terminal Manganese(IV)-Hydroxide Complexes in the Oxidative Electrophilic Reaction.

High-valent transition metal-hydroxide complexes have been proposed as essential intermediates in biological and synthetic catalytic reactions. In this work, we report the single-crystal X-ray structure and spectroscopic characteristics of a mononuclear nonporphyrinic Mn IV -(OH) complex, [Mn IV (Me 3 -TPADP)(OH)(OCH 2 CH 3 )] 2+ ( 2 ), using various physicochemical methods. Likewise, [Mn IV (Me 3 -TPADP)(OH)(OCH 2 CF 3 )] 2+ ( 3 ), which is thermally stable at room temperature, was also synthesized and characterized spectroscopically. The Mn IV -(OH) adducts are capable of performing oxidation reactions with external organic substrates such as C-H bond activation, sulfoxidation, and epoxidation. Kinetic studies, involving the Hammett correlation and kinetic isotope effect, and product analyses indicate that 2 and 3 exhibit electrophilic oxidative reactivity toward hydrocarbons. Density functional theory calculations support the assigned electronic structure and show that direct C-H bond activation of the Mn IV -(OH) species is indeed possible.