THERMAL AND SPECTROSCOPIC STUDY OF DIALKYL [ALPHA-(4-BENZENEAZOANILINO)-N-BENZYL] PHOSPHONATES AND THEIR PALLADIUM(II) HALIDE-COMPLEXES

The mode of thermal decomposition of diethyl and dibutyl esters of [al pha-(4-benzeneazoanilino)-N-benzyl]phosphonic acid and their palladium (II) dihalide adducts, Pd(L)(2)X(2) (L=organophosphorous ligand; X=Cl, Br), as well as cyclopalladated complexes, [Pd(LH)CI](2), have been i nvestigated by thermal (TG, DTA) and spectroscopic (IR, FAB-mass) anal yses. Thermal decomposition of the complexes takes place through a mul tistep process, the first step being a dehalogenation along with deest erification, followed by a complex pyrolysis that leads to a mixture o f Pd and P2O5. All complexes are anhydrous, and on the basis of their initial decomposition temperatures, the thermal stability follows the order Pd(L)(2)Cl-2 < Pd(L)(2)Br-2 < [Pd(L-H)Cl](2). The mass spectrome tric data indicate differences in the gasphase fragmentation pathways between the two types of metal complex and a scheme for their thermal decomposition is proposed. In the adducts the main fragmentation route s consist of sequential losses of HCl giving arise to the mono- and bi s-orthometallated species. The primary decomposition step in the cyclo metallated complexes is shown to be the loss of Cl-.. In both derivati ves these processes are in competition with the loss of the phosphonat e ester group.