Phosphorus–fluorine chemistry. Part XXXV. Unsymmetrical 1,3-diaza-2,4-diphosphetidines of zwitterionic structure

Abstract

The reactions of 2,2,2,4,4,4-hexafluoro-1,3-dimethyl-1,3-diaza-2,4-diphosph(V)etidine with NN′-dilithio-NN′-dimethylethylenediamine, and of the 1,3-t-butyl analogue with t-butyl-lithium gave rise to zwitterionic species, involving tetra- and hexa-co-ordinate phosphorus atoms, instead of the products of normal nucleophilic substitution in which phosphorus retains co-ordination number five. The zwitterionic structure of these products has been established by ¹H, ¹⁹F, and ³¹P n.m.r. spectroscopy. Mass spectroscopy has shown that decomposition into monomeric phosphine imides, which is characteristic of 1,3-diaza-2,4-diphosph(V)etidines, does not occur in the case of the zwitterionic compounds.