Water-soluble complexes MX2L2 (M = Pd, Pt; L = PPh2(C6H4-p-SO3K)): Synthesis, stereoisomerism, and catalytic activities for aromatic cyanation in n-heptane/water biphasic solution

Reaction of (COD)MX2 (M = Pd, Pt; X = Cl, I; COD = 1,5-cyclooctadiene) and P(C6H5)2(C6H4-p-SO3K) afforded water-soluble complexes MX2{P(C6H5)2(C6H4-p-SO3K)}2 (M = Pd; X = Cl (1), M = Pt; X = Cl (2), I (3)) in high yields. Complexes 1–3 were fully characterized by various spectroscopic methods (IR, 1H-, 13C{1H}- and 31P{1H}-NMR spectroscopy) and elemental analyses. For 1 and 3, a mixture of the cis- and trans-isomer was produced from the reaction. For 2, however, only the cis-isomer was obtained. The stereochemistry of 1–3 can be assigned by the chemical shifts and the 1J(Pt–P) values in 31P{1H}-NMR spectral data. The ratios of the cis/trans isomers of 1 and 3 obtained from reactions in a range of solvents with various dielectric constants resulted in a little variation. However, addition of aqueous potassium halide solution to a DMSO-d6 solution of 1 and 3 considerably increased the ratio of the cis/trans, respectively, indicating a strong intramolecular interligand Coulombic repulsion between the ionic phosphine ligands is present. Catalytic cyanation of aromatic iodide with KCN/ZnCl2 in n-heptane/water biphasic system has been tested in the presence of 1–3 with base.