Ruthenium complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane for atom and group transfer reactions

Abstract

With support by macrocyclic tertiary amine ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Me 3tacn), a number of mononuclear metal-ligand multiple bonded complexes have been isolated. Starting with a brief summary of these complexes, the present review focuses on ruthenium-oxo and -imido complexes of Me 3tacn. A family of monooxoruthenium(IV) complexes [Ru IV(Me 3tacn)O(N-N)] 2+ (N-N=2,2′-bipyridines) and a cis-dioxoruthenium(VI) complex cis-[Ru VI(Me 3tacn)O 2(CF 3CO 2)] + have been isolated, and the structures of [Ru IV(Me 3tacn)O(bpy)](ClO 4) 2 (bpy=2,2′-bipyridine) and cis-[Ru VI(Me 3tacn)O 2(CF 3CO 2)]ClO 4 have been determined by X-ray crystallography. Oxidation of [Ru III(Me 3tacn)(NHTs) 2(OH)] (Ts=p-toluenesulfonyl) with Ag + and electrochemical oxidation of [Ru III(Me 3tacn)(H 2L)](ClO 4) 2 (H 3L=α-(1-amino-1-methylethyl)-2-pyridinemethanol) are likely to generate ruthenium-imido complexes supported by Me 3tacn. DFT calculations on cis-[Ru VI(Me 3tacn)O 2(CF 3CO 2)] + and proposed ruthenium-imido complexes have been performed. Complexes [Ru IV(Me 3tacn)O(N-N)] 2+ are reactive toward alkene epoxidation, and cis-[Ru VI(Me 3tacn)O 2(CF 3CO 2)] + efficiently oxidizes various organic substrates including concerted [3+2] cycloaddition reactions with alkynes and alkenes to selectively afford α,β-diketones, cis-diols, or CC bond cleavage products. Related oxidation reactions catalyzed by ruthenium Me 3tacn complexes include epoxidation of alkenes, cis-dihydroxylation of alkenes, oxidation of alkanes, alcohols, aldehydes, and arenes, and oxidative cleavage of CC, CC, and C-C bonds, all of which exhibit high selectivity. Ruthenium Me 3tacn complexes are also active catalysts for amination of saturated C-H bonds. © 2010 Elsevier B.V.