High-valent ruthenium(IV) and -(VI) oxo complexes of octaethylporphyrin. Synthesis, spectroscopy, and reactivities

Abstract

Oxidation of (Ru{sup II}(OEP)(CO)) (H{sub 2}OEP = octaethylporphyrin) by m-chloroperoxybenzoic acid in methanol gave (Ru{sup VI}(OEP)(O){sub 2}), isolated as air-stable diamagnetic purpose solid ({mu}{sub eff} {approximately} 0 {mu}{sub B}). (Ru{sup VI}(OEP)(O){sub 2}) shows one intense IR band at 821 cm{sup {minus}1} assignable to {nu}{sub as} (O{double bond}Ru{double bond}O) stretch. In CH{sub 2}Cl{sub 2}, it reacts with olefins to give epoxides and (Ru{sup IV}(OEP)(OH)){sub 2}O in quantitative yields. In alcohols (ROH), the epoxidation reactions give (Ru{sup IV}(OEP)O(ROH)), which readily dimerizes to (Ru{sup IV}(OEP)(OH)){sub 2}O in noncoordinating solvents. (Ru{sup IV}(OEP)O(ROH)) is paramagnetic with measured {mu}{sub eff} of 3.1 {mu}{sub B}. Its {sup 1}H NMR spectrum shows three broad singlets, the paramagnetic isotropic shifts of which vary inversely with temperature. The E{degree} for the (Ru{sup IV}(OEP)O(ROH))/(Ru{sup III}(OEP)O(ROH)){sup {minus}} couple in CH{sub 2}Cl{sub 2}/py (py = pyridine) is {minus}0.86 V vs Cp{sub 2}Fe{sup +/0}. In CH{sub 2}Cl{sub 2}/py solution, (Ru{sup IV}(OEP)O(ROH)) reacts with olefins to give (Ru{sup II}(OEP)(py){sub 2}) and epoxides.