Crystal structure of triphenylphosphine sulfide diiodine; the first crystallographically characterised 1∶1 molecular charge-transfer complex of a tertiary phosphine sulfide with diiodine
Abstract
In CH2Cl2 solution, Ph3PS and diiodine react to form a molecular 1∶1 charge-transfer complex. The complex has been studied in solution using 31P-{H} NMR and UV/VIS spectroscopy. Single-crystal X-ray diffraction and solid-state 31P-{H} NMR studies of Ph3PS·I2 show that the molecular structure is maintained in the solid phase. The structure of Ph3PS·I2 is novel and contradicts previous results which indicated that a 1∶1 (Ph3PS∶I2) complex could not be isolated in the solid state. The I–I distance [2.823(1) Å] and the S–I distance [2.753(2) Å] in Ph3PS·I2 are comparable with those in charge-transfer complexes of related sulfur donors. However, the I–I distance in Ph3PS·I2 is shorter than that in Ph3PSe·I2 reflecting the weaker donor power of the Ph3PS towards diiodine. The NMR spectroscopic results on Ph3PS·I2 and the analogous Ph3PO and Ph3PSe compounds indicate that the stability of the Ph3PE·I2 complexes increases in the order E = Se > S O.