Revisiting the Chemistry of Phosphinidene Sulfides

The reaction of triethylamine with the [4 + 2] cycloadducts of phosphole sulfides and 3-bromo-N-phenyl­maleimide provides a convenient access to phosphinidene sulfides [RPS]. These transient species are trapped by 2,3-dimethyl-1,3-butadiene to give the previously unknown trivalent [4 + 2] cycloadducts. One of these (R = Ph) has been characterized as its P-W­(CO)5 complex by X-ray crystal structure analysis. With cyclopentadiene, the subsequent insertion of a second molecule of [RPS] leads to a new type of bicyclic product containing a thia­diphos­pholane ring.