Isomeric Preference in Complexes of Palladium(II) with Chelating P,N‐Donor Ligands

Square‐planar complexes [PdCl{κ2‐(RN = CHC6H4PPh2)R′}] (R′ = Cl; R = 4‐CH3C6H4, 1a; R = 2‐CH3OC6H4, 1b; R = 2‐HOC6H4, 1c; R′ = CH3; R = 4‐CH3C6H4, 2a; R = 2‐CH3OC6H4, 2b; R = 2‐HOC6H4, 2c) have been prepared and characterized. In complexes 2a–c only formation of one isomer was observed. The Pd–methyl bond arranges in a cis position to the phosphane fragment of the P,N chelating ligand. Reaction of complexes 2a–c in acetonitrile with AgBF4 led to removal of the chlorido ligand and coordination of acetonitrile for 2a. However, for 2b and 2c coordination of the oxygen was observed and the chelating P,N ligands became tricoordinate. DFT calculations developed on models of the complexes displayed that the isomer with the methyl ligand coordinated in the cis position to the phosphane ligand were harder (or had a bigger HOMO/LUMO gap)(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)