Deprotonation-Induced Structural Changes in SNS-Pincer Ruthenium Complexes with Secondary Thioamide Groups

The reaction of [Ru­(CO)2Cl2]n with a SNS-pincer ligand (PhSNS·2H) containing two secondary thioamide (−CSNH−) groups afforded a cationic Ru complex with a Cl– counteranion, [RuCl­(CO)2(PhSNS·2H)]­Cl. The stepwise deprotonation of the two secondary thioamide groups of the above complex afforded neutral mononuclear [RuCl­(PhSNS·1H)­(CO)2] and dinuclear [Ru­(PhSNS)­(CO)2]2 complexes, with the successive elimination of two HCl molecules. The SNS-pincer ligand functions as a mono- or dianionic ligand with iminothiolate groups after the successive deprotonation steps. The metal-bridging ability of the iminothiolate groups enables the formation of the dinuclear complexes. The IR spectra of the complexes show that the deprotonation of the ligand increases the electron density at the Ru center. The substituents on the secondary thioamide groups in the SNS-pincer ligand influence the deprotonation properties and redox potentials of the complexes; for example, a change in the substituents from a phenyl to a benzyl group decreased the deprotonation ability and oxidation potential of the Ru center.