Preparative and spectroscopic studies of some phosphorus (V) chloride and bromide derivatives

Abstract

Further preparative and Raman spectroscopic investigations of products derived from reactions of phosphorus (III) halides, boron trihalides and halogens have been made. A new compound of empirical formula P2BCl13 has been formulated as [equations] and may be considered as the parent of a series involving the [equations] cations. The structural implications of the proposed single halide anions and the relationship of the compounds to metastable PCl5 (Phase III) is discussed; changes which occur on heating have been monitored by Raman and magic angle rotation NMR spectroscopy. A further compound analogous to P2Cl9Br has been reported. The compounds MePCl4, Me2PCl3 and Me3PCl2 were prepared and 31Raman and P magic angle rotation NMR measurements support ionicformulations containing single halide ions. Complexes of these withLewis acids were made and the characteristic shifts associated withthe presence of single halide ions in the Raman spectra of the phosphonium cations were observed. Mixed chlorobromo cations ofthese methylphosphoranes were prepared and their Raman spectrapartially assigned. Conventional matrix isolation as well as low temperature sublimation experiments were performed on the vapours above PCl5, PBr5 and MePCl4. Monomeric species were observed for both PCI5 and MePCl4 but decomposition occurred with PBr5. In these studies Raman spectra were monitored from 15K to ambient temperatures and the conversion of covalent to ionic species was observed.