Structural, Electronic, and Thermochemical Preference for Multi‐PCET Reactivity of Ruthenium(II)‐Amine and Ruthenium(IV)‐Amido Complexes

Abstract

AbstractThe 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 [RuII(bpy)(en*)2]2+ (RuII‐H0) and [RuIV(bpy)(en*‐H2)2]2+ (RuIV‐H2) 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 favoring 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.