Palladium(II) complexes with polyphosphazene

Abstract

AbstractAn allylphenoxy‐substituted polyphosphazene has been modified via inorganic chemical concepts. The transition metal salt is bis(acetonitrile)dichloropalladium(II). The coordination complexes have been characterized using acid‐base solution chemistry, sol‐gel phase transitions, thermomechanical property measurements and infrared spectroscopy. Solid complexes of polyphosphazene and PdCl2 cannot be dissolved in the original solvent (i.e., tetrahydrofuran) used during sample preparation. These polymeric palladium complexes also cannot be disrupted by a stronger base, like triphenylphosphine. There is a monotonic increase in the glass transition temperature at higher concentrations of palladium chloride. Tg of the pure polymer increases by 21°C in the presence of 10 mol% palladium chloride. The increase in high‐strain mechanical properties cannot be explained solely by a “filler effect.” At higher PdCl2 concentrations, there is a direct correlation between the enhancement in Tg, higher mechanical fracture stress, and increased infrared absorbance @ 1092 cm−1 because of the formation of a palladium‐π‐complex with allylic substituents in the phenoxy sidegroup. Palladium chloride relinquishes its acetonitrile ligands after dissolution in THF, and the vacant sites in the first‐shell coordination sphere of the transition metal are occupied by these allylic substituents in the sidegroup. This produces interchain coordination crosslinks, which modify the thermomechanical properties of polyphosphazene/ PdCl2 complexes.