On the borderline between cis and trans in organometallic (phosphane)platinum(II) complexes

The borderline between the cis and trans configurations in square-planar diarylplatinum(ii) complexes with triethylphosphane ligands [Pt(Ar)(2)(PEt3)(2)] [Ar = 2,4,6-trimethylphenyl (mesityl), 2,6-dimethylphenyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl and phenyl] has been investigated by a combination of multinuclear (H-1, C-13, P-31 and Pt-195) NMR spectroscopy, X-ray crystallography and quantum chemical (DFT) calculations. When formed under thermodynamic conditions, the complexes show a clear cutoff between cis (tolyl and phenyl complexes) and trans (2,6-xylyl and mesityl complexes). The syn and anti stereoisomers were identified for the 2-methylphenyl and 3-methylphenyl derivatives. Calculated data (structural isomers or NMR) are in excellent agreement with experimental findings. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.