The reaction of carbolic acids with tetraphospha trichalcogena diiodides in CS2 solution

Abstract

alpha-P4E3(I)R and alpha-P4E3R2 (E = S and/or Se) have been identified by P-31 n.m.r. spectroscopy in reaction solutions of alpha-P4E3I2 and carbolic acids with pK(s) values 23 in presence of triethylamin. Similar products were obtained in comparable yields with carbolic acids, having pK(s) values <3, only by the reaction with their tin organic derivates. The chemical shifts of the ligand carrying phosphorus atoms are depending on the electronegativity of oxygen, in addition to the inductive effect of the organic group connected to the carboxyl group. Chemical shifts and coupling constants of alpha-P4E3(I)R can be calculated from the symmetric compound alpha-P4E3I2 and alpha-P4E3R2. Deviations between calculated and measured values of side and bridge coupling constants indicate a torsion of the molecular skeleton due to the large size difference between the two ligands. An endocyclic replace ment of sulfur by selenium in alpha-P4S3R2 revealed significant differences in the behaviour of the side couplings, as compared with alpha-P4SnSe3-nI2, which are probably due to an interaction of the carboxyl ligand with its chalcogen neighbour.