Dimethylplatinum(II) and tetramethylplatinum(IV) complexes of 1-methyl-(2-alkylthiomethyl)-1 H-benzimidazoles: experimental and DFT-calculated structures and NMR spectra

Abstract

The compounds (L)PtMe n where n=2 or 4 and L=mmb (1-methyl-(2-methylthiomethyl)-1 H-benzimidazole) or L=mtb (1-methyl-(2- tert-butylthiomethyl)-1 H-benzimidazole) were characterized by X-ray crystallography (except for (mtb)PtMe 2) and by 1H- and 195Pt-NMR spectroscopy. The tetramethylplatinum(IV) complexes exhibit a variable degree of dynamic 1H-NMR behavior due to the mobility at the thioether sulfur atom in the non-planar five-membered chelate ring, as supported by structural analysis. Density-functional theory (DFT) calculations were used to reproduce the structural features and the 1H-NMR chemical shifts. In comparison with other late transition metal complexes of these NS chelate ligands the Me 4Pt and especially the Me 2Pt compounds exhibit a relatively stronger preference of the metal for the sulfur donor.