Chemical properties of 3a,6a-diaza-1,4-diphosphapentalene. Addition of polyhalohydrocarbons

Abstract

3a,6a-Diaza-1,4-diphosphapentalene (DDP, 1), in contrast to common azaphospholes, readily reacts with polyhalohydrocarbons with the formation of 1,1- or 1,4-addition products at the phosphorus atoms. Dibromomethane gives the substitution product of two bromine atoms [CH₂(DDP)₂]Br₂ (2) and diphosphine (DDP-DDP)Br₂ (3) containing a bridging bromine atom. In the course of the reaction of DDP with CF₂Br₂, two products of sequential substitution of the bromine atoms were isolated, which are 1,4-Br₂(DDP) (6) and [CF₂(DDP)₂]Br₂ (7). Tris(pentafluorophenyl)phosphine reacts with DDP at the C—F bond with the formation of 1,1-addition product 8. Compounds 2, 3, 7, and 8 contain hypervalent (tervalent 4-coordinated) phosphorus atoms. X-ray diffraction data indicate that the mutual arrangement of the DDP fragments in compounds 2, 3, and 7 is determined by the non-covalent interaction of one of the bromine atoms simultaneously with two phosphorus atoms of different DDP fragments in such a way that the lines of the N—P bonds converge at this bromine atom.