Phosphorus sulfur trichloride adducts

Numerous adducts of MX4 with nitrogen, phosphorus, arsenic, oxygen and sulfur donors have been obtained, mainly for niobium with X = CI or Br7 (Tables 29-33). The absence of MF4 adducts, except for [NbF4(py)2],511 may be due less to their instability than to a lack of investigations. An ill-defined fluoro trichloride complex, [NbCl3F(MeCN)2.65], has also been reported.512... 

In spite of its highly strained Dewar structure 1 is stable and may be kept in a refrigerator for several years. It isomerizes to the aromatic isomer at high temperature (half-life in benzene at 160 C was 5.1 h). The treatment of the Dewar thiophene with triphenylphosphine did not cause the elimination of sulfur, but instead accelerated the isomerization to the aromatic isomer. This catalytic acceleration is limited to tervalent phosphorus compounds but phosphorous trichloride or phenyldichlorophosphine are ineffective. An adduct of diphenylchlorophosphine with the Dewar thiophene was postulated to be a ff-complex with a P—S bond. It decomposed spontaneously to the thiophene and the phosphine as shown in Eq. (9).15 Recently,... 

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