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

With support by macrocyclic tertiary amine ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Me(3)tacn), 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(3)tacn. A family of monooxoruthenium(IV) complexes [Ru-IV(Me(3)tacn)O(N-N)](2+) (N-N = 2,2' -bipyridines) and a cis-dioxoruthenium(VI) complex cis-[Ru-VI(Me(3)tacn)O-2(CF3CO2)](+) have been isolated, and the structures of [Ru-IV(Me(3)tacn)O(bpy)](ClO4)(2) (bpy = 2,2'-bipyridine) and cis-[Ru-VI(Me(3)tacn)O-2(CF3CO2)]ClO4 have been determined by X-ray crystallography. Oxidation of [Ru-III(Me(3)tacn)(NHTs)(2)(OH)] (Ts = p-toluenesulfonyl) with Ag+ and electrochemical oxidation of [Ru-III(Me(3)tacn)(H2L)](ClO4)(2) (H3L = alpha-(1-amino-1-methylethyl)-2-pyridinemethanol) are likely to generate ruthenium-imido complexes supported by Me3tacn. DFT calculations on cis-[Ru-VI(Me(3)tacn)O-2(CF3CO2)](+) and proposed ruthenium-imido complexes have been performed. Complexes [Ru-IV(Me(3)tacn)O(N-N)](2+) are reactive toward alkene epoxidation, and cis-[Ru-VI(Me(3)tacn)O-2(CF3CO2)](+) efficiently oxidizes various organic substrates including concerted [3+2] cycloaddition reactions with alkynes and alkenes to selectively afford alpha,beta-diketones, cis-diols, or C=C bond cleavage products. Related oxidation reactions catalyzed by ruthenium Me(3)tacn complexes include epoxidation of alkenes, cis-dihydroxylation of alkenes, oxidation of alkanes, alcohols, aldehydes, and arenes, and oxidative cleavage of C=C, C=C, and C-C bonds, all of which exhibit high selectivity. Ruthenium Me3tacn complexes are also active catalysts for amination of saturated C-H bonds. (C) 2010 Elsevier B.V. All rights reserved.