Formation of Transient and Stable 1,3-Dipole Complexes with P,S,C and S,P,C Ligand Skeletons

Reaction of Li/Cl phosphinidenoid complexes 2a,b with diphenyl thioketone or N,N′-tetramethylthiourea yielded the bicyclic 1,2-thiaphospholane complex 4b or alkylidene­(thioxo)­phosphane complex 6a, respectively. DFT studies provide insight into the reaction pathways, pointing to the initial thiocarbonyl–phosphane–ylide complex 3, which can form the bicyclic 1,2-thiaphospholane complex 4. However, cyclization to give thiaphosphirane complex 5 also appears to be feasible, which via subsequent combined C–S bond cleavage and P-to-S haptotropic metal complex shift yields complex 6.