The reaction of tertiary aryl phosphites with diiodine at ambient temperatures; structural characterisation of the tertiary phosphite tetraiodides (PhO)3PI4, (4-MeC6H4O)3PI4 and (2,4-But2C6H3O)3PI4

Abstract

The reaction of the tertiary phosphites (RO)₃P (R = Ph, 4-MeC₆H₄, 4-Bu^tC₆H₄, 2,4-Bu^t₂C₆H₃, 2,6-Me₂C₆H₃, 2,4,6-Me₃C₆H₂ or 2-PhC₆H₄) with one and two mole equivalents of diiodine has been investigated. In all cases the tetra-iodide compounds (RO)₃PI₄ were isolated regardless of the stoichiometry employed. The three compounds (RO)₃PI₄ (R = Ph, 4-MeC₆H₄ or 2,4-Bu^t₂C₆H₃) have been crystallographically characterised for comparative purposes and represent the first examples of crystal structures for compounds of this formula. The structural characterisation of these compounds illustrates the structural dependence of (RO)₃PI₄ compounds on R. For (RO)₃PI₄ (R = Ph or 2,4-Bu^t₂C₆H₃) the compounds exist as discrete molecular species whereas, for R = 4-MeC₆H₄ the triiodide fragments of discrete molecules link via long-range I–I interactions to form a dimer. Additionally, d(I–I) for the (RO)₃PI and I₃ fragments is sensitive to R, being 3.227(1) Å for (2,4-Bu^t₂C₆H₃O)₃PI₄ and 3.3888(7) Å for (PhO)₃PI₄. In contrast to the analogous R₃PI₄ compounds, which show great variation in δ in their ³¹P-{¹H} NMR spectra depending on R, the (RO)₃PI₄ compounds described all exhibit quite similar δ values irrespective of R.