Reactivity of ammonium and iminium tetraphenylborates towards Pd(0)-complexes: selective allyl or proton transfer to Pd(0).: Evidence of formation of the species [HPd(dppe)2][BPh4]

The reactivity of ammonium- and iminium-BPh4 salts, [CH2CHCH2NH3]BPh4, [(CH2CHCH2)HNCMe2]BPh4 and [(PhCH2)HNCMe2]BPh4, towards Pd(0)-complexes, [Pd(dppe)(dba)] and [Pd(dppe)2] (dppe=1,2-bis(diphenylphosphino)ethane; dba=dibenzylideneacetone), has been investigated. Allyl-ammonium and -iminium tetraphenylborates [CH2CHCH2NH3]BPh4 and [(CH2CHCH2)HNCMe2]BPh4 react with [Pd(dppe)(dba)] to afford, under mild conditions (293 K), [(η3-C3H5)Pd(dppe)][BPh4], through selective oxidative transfer of allyl group from the ammonium or iminium cation to the Pd center. [(PhCH2)HNCMe2]BPh4 reacts with [Pd(dppe)2] to afford [HPd(dppe)2][BPh4], that, under the reaction conditions, has poor stability as it undergoes hydride transfer to the iminium ion present in the reaction medium, affording [Pd(dppe)2][BPh4]2.