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.