Effects of the intramolecular NH•••S hydrogen bond in mononuclear platinum(II) and palladium(II) complexes with 2,2′-bipyridine and benzenethiol derivatives

A series of complexes, [M(bpy)(SAr)21 (M = platinum(II) or palladium(II), bpy = 2,2'-bipyridine, SAr = 2- or 4-(acylamino)benzenethiolate, or 2-(alkylcarbamoyl) benzenethiol ate), were synthesized and characterized on the basis of H-1 NMR, IR, and electrochemical properties. The structures of [Pt(bpy)(S-2-Ph3CCONHC6H4)(2)] (1) and (Pt(bpy)(S-2-t-BuNHCOC6H4)(2)] (3) were determined by X-ray analysis. The complexes have intramolecular (NHS)-S-... hydrogen bonds between the amide NH group and the sulfur atom. A weak (NHS)-S-... hydrogen bond in these complexes and [Pd(bpy)(S-2-Ph3CCONHC6H4)(2)] (4) is detected from the H-1 NMR spectra and the IR spectra in chloroform and. in the solid state. [Pt(bpy)(S-2-Ph3CCONHC6H4)(2)] (1) exhibits a remarkably high-energy-shifted lowest-energy band in UV-visible spectra and has a positively shifted oxidation potential. The blue-shift of 42 nm and the positive shift of +0.24 V, as compared to those of [Pt(bpy)(SC6H5)(2)], are due to the effect of the (NHS)-S-... hydrogen bond.