Synthesis of the first stable pentaco-ordinate 1,2-thiaphosphetene

Pentacoordinate 1,2-thiaphosphetenes bearing the Martin ligand were synthesized:by the reaction of the corresponding phosphorus ylide with isophiocyanates. Their mass and NMR spectral data showed that they have 1:2 adducts of the phosphorus ylide and isothiocyanates, which have a distorted trigonal bipyramid with oxygen and sulfur atoms at the apical positions. Thermolysis of the phenyl isothiocyanate adduct gave the corresponding cyclic thiophosphinate as a phosphorus-containing product in almost quantitative yield.