The reaction of the tertiary phosphine sulfides R3PS (R = Ph, Me2N or C6H11) with X2 (X2 = I2, Br2, IBr or ICl); structural characterisation of the CT complexes (Me2N)3PSI2 and Ph3PS(I0.89Br0.11)Br and the ionic compound [{(Me2N)3PS}2S]2+ 2[Br3]–

Abstract

The reactions of the tertiary phosphine sulfides R₃PS (R = Ph, Me₂N or C₆H₁₁) with X₂ (X = I or Br) and IX (X = Br or Cl) have been studied. Reaction of R₃PS with I₂ or IX results in quantitative isolation of the CT complexes R₃PSIX (X = I, Br or Cl), except for Ph₃PS with I₂ which produces the unusual compound (Ph₃PSI₂)₂I₂, which has been crystallographically characterised by earlier workers. The crystal structure of (Me₂N)₃PSI₂ has been determined and compared to Ph₃PSI₂, previously described. The greater d(I–I) for (Me₂N)₃PSI₂, 2.856(1) Å, compared to that of 2.823(1) Å for Ph₃PSI₂ clearly illustrates that d(I–I) in R₃PSI₂ compounds is sensitive to R, although this effect is less pronounced when compared to that of analogous R₃PSeI₂ compounds. The crystal structure of the product from the reaction of Ph₃PS with IBr has also been determined and represents the first example of a tertiary phosphine sulfide interhalogen CT complex. It has the formula Ph₃PS(I_0.89Br_0.11)Br and is isomorphous with Ph₃PSI₂. The reaction of R₃PS with Br₂ is complex. In the case of Ph₃PS, phosphorus–sulfur bond cleavage occurs quantitatively to produce Ph₃PBr₂ and elemental sulfur. Reaction of (Me₂N)₃PS with Br₂ gives, as one product, [{(Me₂N)₃PS}₂S][Br₃]₂ in moderate (ca. 30%) yield. This unusual dication is compared to the previously reported [(Bu^t₃PTe)₂Te][SbF₆]₂. Tricyclohexylphosphine sulfide reacts with Br₂ in solvents of low relative permittivity (Et₂O) to produce the 1∶1 addition complex (C₆H₁₁)₃PSBr₂; however, dissolution of this material in solvents of higher relative permittivity results in phosphorus–sulfur bond cleavage to produce (C₆H₁₁)₃PBr₂ and elemental sulfur.