Definitive Evidence for the Insertion of Terminal Alkynes into ArylSPt Bonds: “o‐Halogen Effect” in Stoichiometric and Catalytic Reactions

An unexpected acceleration of the insertion of terminal alkynes into the SPt bond of complexes 1 was observed when an o-halogen substituent was present in the SAr moiety (see scheme). The reaction rates for G=o-Cl, o-Br, or o-I were much greater than for electron-donating or electron-withdrawing groups. This “o-halogen effect” was also found to be relevant to the Pd-catalyzed addition of (ArS)2 to alkynes.