A series of RuII -polypyridyl complexes of the design [RuII (tpy)(NN)X]n+ (tpy = 2,2′:6′,2′′-terpyridine; NN = bidentate polypyridine; X = Cl− or CH3CN; n = 1 or 2) have been synthesized and analyzed for their ability to function as electrocatalysts in the reduction of CO2 to CO. Varying the electron-donating/withdrawing character of the NN polypyridyl ligand has allowed for modification of electron density at the formally RuII metal center. Complexes where X = Cl− display ligand substitution for CH3CN with differing rates of Cl− dissociation (k–Cl), therefore providing a degree of insight into the electron density and thus the chemical activity at the RuII center. Detailed analysis of the cyclic voltammograms under argon vs. CO2 atmospheres using multiple switching potentials and scan rates ranging from ν = 25–2000 mV s−1 has painted a picture of how monodentate ligand lability due to NN polypyridyl electron-donating character is related to electrocatalytic CO2 reduction activity of RuII -polypyridyl complexes. From these studies, multiple mechanistic pathways towards generating the catalytically active [Ru(tpy−)(NN−)CO2]0 species are proposed and differ via the order of electrochemical and chemical processes. © 2014 The Partner Organisations.