The reaction of some tertiary phosphines with two mole equivalents of diiodine to produce the iodophosphonium triiodides [R3PI]I3; influence of R in causing subtle variations in solid state structures
Abstract
A variety of R3PI4 compounds have been synthesized and characterised by elemental analysis, NMR and visible spectroscopy. Apart from Ph3PI4, all are reported for the first time. X-Ray crystallographic studies on two of these materials, Pri3PI4 and (Prn2N)3PI4, revealed different solid-state structures which are, in turn, different to both the two polymorphs of Ph3PI4 and Fc3PI4 (Fc = ferrocenyl) the crystal structures of which have been previously reported. The compound Pri3PI4 exists as [(IPPri3)2I3]I3, which contains two [IPPri3]+ cations independently weakly linked to one of the two terminal iodine atoms of the same triiodide anion. The structure also contains a discrete triiodide anion. The compound (Prn2N)3PI4 exhibits very little anion–cation interaction. Of the two molecules present in the asymmetric unit, one exhibits no anion–cation interaction, while the other shows only a very weak contact [d(I–I)] (cation–anion) = 3.944(2) Å.