Coordinating Tectons: Bimetallic Complexes from Bipyridyl Terminated Group 8 Alkynyl Complexes

Bipyridyl appended ruthenium alkynyl complexes have been used to prepare a range of binuclear homometallic ruthenium and heterometallic ruthenium–rhenium complexes. The two metal centers are only weakly coupled, as evinced by IR and UV–vis–near NIR spectroelectrochemical experiments and supported by quantum chemical calculations. The alkynyl complexes of the type [Ru(C≡Cbpy){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-κ2-N′N-RuClCp)(PPh3)2Cp] undergo two essentially reversible oxidations, the first centered on the (C2bpy-κ2-N′N-RuClCp) moiety and the second on the Ru(C≡Cbpy)(PPh3)2Cp fragment, leading to radical cations that can be described as Class II mixed-valence complexes. The heterometallic binuclear complexes [Ru(C2bpy-κ2-N′N-ReCl(CO)3){Ln}] display similar behavior, with initial oxid...