Synthesis, electrochemistry, and reactivities of trans-[RuVI(L)O2]2+ (L = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)propylenediamine

Abstract

The synthesis and characterization of the ligand N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-propylenediamine (L) and the complex trans-[RuVI(L)O2]2+ are described. The complex has been characterized by u.v.-visible [dxy → dπ* (dπ* = dxz,dyz) at 380-420 nm] and i.r. [νasym(RuO2) at 860 cm-1] spectroscopy. At pH 1.0 it exhibits three reversible couples RuVI-RuIV, RuIV-RuIII, and RuIII-RuII at potentials of 0.89, 0.60, and 0.28 V respectively vs. saturated calomel electrode. The RuVI-RuIV couple splits into two reversible one-electron couples RuVI-RuV and RuV-RuIV in alkaline solutions (pH > 9). The complex is a powerful oxidant, capable of oxidizing toluene to benzaldehyde, alcohols to aldehydes/ketones, tetrahydrofuran to γ-butyrolactone, and norbornene to exo-2,3-epoxy-norbornane in high yields at room temperature. Oxidation of cis- and trans-stilbenes gave benzaldehyde and trans-stilbene oxides.