Multiple Isomerism (<i>cis/trans</i>; <i>s</i><i>yn/</i><i>a</i><i>nti</i>) in [(dmso)₂Pt(aryl)₂] Complexes: A Combined Structural, Spectroscopic, and Theoretical Investigation

The occurrence of cis or trans configurations in square planar diarylbis(dimethyl sulfoxide)platinum(II) complexes with S-bonded dmso ligands and aryl = 2,3,4,5,6-pentamethylphenyl, 2,4,6-trimethylphenyl, 2,6-dimethylphenyl, 2-, 3-, and 4-methylphenyl, and phenyl has been investigated by multinuclear (1H, 13C, and 195Pt) NMR spectroscopy and crystal structure analysis. Both methods confirm the cis configuration for complexes with the smaller phenyl and methylphenyl (tolyl) ligands and the trans configuration for the compounds with the bulkier ligands, starting from 2,6-dimethylphenyl. Spectroscopic criteria could thus be established to identify configurational isomers. For the 2-tolyl complex an additional kind of isomerism arises from the relative orientation of the two methyl substituents on the same side (syn) or on different sides of the coordination plane (anti). 2D-NMR spectroscopy allowed us to identify the conformers and to study isomerization mechanisms. DFT calculation results agree well with the experimental structures and with the spectroscopic data.