Structural isomerism involving an ambidentate ligand: the synthesis and characterization of diselenocyanato [bis(diphenylphosphino)methane] palladium(II) and cyano(selenocyanato) [diphenyl(diphenylphosphinomethyl)phosphine selenide] palladium(II)

The reaction, at 25 °C in methanol, between [Pd(SeCN)4]2− and bis(diphenylphosphino)methane (dpm) has been found to produce cyano(selenocyanato) [diphenyl(diphenylphosphinomethyl) phosphine selenide]palladium(II), [Pd(dpmSe)(CN)(SeCN)], wherein the cyanide group is trans to an Se atom which has been inserted into one PdP bond, and the selenocyanate group is trans to the unchanged diphenylphosphino group. The structure has been confirmed by the results of a single crystal X-ray diffraction study. The structural isomer, [Pd(dpm)- (SeCN)2], of the foregoing complex has also been prepared by the reaction of Pd(C2H3O2)2 with dpm, followed by reaction with KSeCN. Heating the [Pd(dpm)(SeCN)2] isomer converts it into [Pd- (dpmSe)(CN)(SeCN)]. A mechanism is proposed for the isomerization which involves an intramolecular selenium atom insertion.