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.