Reactivity and electrochemical behavior of ruthenium dithiolene complexes with coordinatively unsaturated metal centers: cycloaddition and dimerization reactions

The ruthenium dithiolene complex [(C6H6)Ru{S2C2(COOMe)2}] (1a) coexisted with the corresponding dimer [(C6H6)Ru{S2C2(COOMe)2}]2 (1a′) in solution, and complex 1a reacted with acetylenes or diazo compounds to give the alkene-bridged adducts [(C6H6)Ru{S2C2(COOMe)2}{C2(COOR)2}] (R = Me (2a), Et (3a)) or the alkylidene-bridged adducts [(C6H6)Ru{S2C2(COOMe)2}(CHR)] (R = H (4a), SiMe3 (5a), COOEt (6a)). The oxidant of complex 1a was immediately converted to the corresponding cationic dimer 1a′+, and the neutral complex 1a was regenerated when it was re-reduced.