文摘
Bipyridyl appended ruthenium alkynyl complexes have been used to prepare a range of binuclear homometallic ruthenium and heterometallic ruthenium鈥搑henium complexes. The two metal centers are only weakly coupled, as evinced by IR and UV鈥搗is鈥搉ear NIR spectroelectrochemical experiments and supported by quantum chemical calculations. The alkynyl complexes of the type [Ru(C鈮bpy){Ln}] ({Ln} = {(PPh3)2Cp}, {(dppe)Cp*}, {Cl(dppm)2}) undergo reversible one-electron oxidations centered largely on the alkynyl ligands, as has been observed previously for closely related complexes. The homometallic binuclear complexes, exemplified by [Ru(C2bpy-魏2-N鈥?i>N-RuClCp)(PPh3)2Cp] undergo two essentially reversible oxidations, the first centered on the (C2bpy-魏2-N鈥?i>N-RuClCp) moiety and the second on the Ru(C鈮bpy)(PPh3)2Cp fragment, leading to radical cations that can be described as Class II mixed-valence complexes. The heterometallic binuclear complexes [Ru(C2bpy-魏2-N鈥?i>N-ReCl(CO)3){Ln}] display similar behavior, with initial oxidation on the ruthenium fragment giving rise to a new optical absorption band with Re 鈫?Ru(C鈮bpy) charge transfer character. The heterometallic complexes also exhibit irreversible reductions associated with the Re hetereocycle moiety.