Abstract
The multiredox reactivity of bioinorganic cofactors is often coupled to proton transfers. Here we investigate the structural, thermochemical, and electronic structure of ruthenium-amino/amido complexes with multi- proton-coupled electron transfer reactivity. The bis(amino)ruthenium(II) and bis(amido)ruthenium(IV) complexes [Ru(II)(bpy)(en*)(2)](2+) (Ru(II)-H(0) ) and [Ru(IV)(bpy)(en*-H(2))(2)](2+) (Ru(IV)-H(2) ) interconvert reversibly with the transfer of 2e(-)/2H(+) (bpy = 2,2'-bipyridine, en* = 2,3-diamino-2,3-dimethylbutane). X-ray structures allow correlations between the structural and electronic parameters, and the thermochemical data of the 2e(-)/2H(+) multi-square grid scheme. Redox potentials, acidity constants and DFT calculations reveal potential intermediates implicated in 2e(-)/2H(+) reactivity with organic reagents in non-protic solvents, which shows a strong inverted redox potential favouring 2e(-)/2H(+) transfer. This is suggested to be an attractive system for potential one-step (concerted) transfer of 2e(-)and 2H(+) due to the small changes of the pseudo-octahedral geometries and the absence of charge change, indicating a relatively small overall reorganization energy.