Transition‐Metal‐Like Reversible Cycloadditions of [ t BuSP‐W(CO) 5 ] with Alkenes and Alkynes

tert ‐Butylthiophosphinidene complex [ t BuSP‐W(CO) 5 ] was generated by dissociation of 1‐( tert ‐butylthio)phosphirane–W(CO) 5 complex under mild conditions. The formation of transient [ t BuSP‐W(CO) 5 ] was indicated by trapping reactions with 2,3‐dimethyl‐1,3‐butadiene, alkynes, phenanthrene‐9,10‐dione, and methanol. The LUMO of [MeSP‐W(CO) 5 ] is significantly lower in energy than those of [Me 2 NP‐W(CO) 5 ], [MeOP‐W(CO) 5 ], and [Me 2 PP‐W(CO) 5 ]. The HOMO of [MeSP‐W(CO) 5 ] contains a significant contribution from the in‐plane lone pair of P and the LUMO shows a typical π * characteristic. Since stabilized by sulfur lone pair and coordinated by W(CO) 5 , [ t BuSP‐W(CO) 5 ] undergoes facile and reversible cycloadditions with alkenes and alkynes.