Synthesis and Reactivity of Neutral Palladium(II) Alkyl Complexes that Contain Phosphinimine-Arenesulfonate Ligands

The synthesis and characterization of ortho-phosphiniminium-arenesulfonate zwitterions 1a–1d, the corresponding sodium salts 3a–3d, methyl­(pyridine)­palladium­(II) complex 4a, and methyl­(4-tert-butyl­pyridine)­palladium­(II) 5a–5d complexes are reported. Complex 4a suffers from limited solubility in aromatic hydrocarbons, while 5a–5d are soluble in benzene and toluene. Complex 5a forms a tridentate orthopalladated species 6a upon heating to 80 °C in toluene. Introduction of alkyl substituents on the phosphinimine phosphorus atom retards orthopalladation, and the (nBu)3P functionalized complex 5d does not undergo orthopalladation after heating at 80 °C for 24 h. The Pd–C bond in the orthopalladated complex 6a is inert toward ethylene insertion. Complexes 5a–5d do not react with ethylene at 80 °C and decompose to Pd0 and zwitterions 1a–1d.