A half-sandwich thiolatoiridium complex bearing a five-membered C–S chelating ligand has been synthesized via cyclometalation of triphenylmethyl mercaptan. The thiametallacycle crystallizes as a coordinatively saturated dimer, bridged with the thiolato ligand. Two-electron donors, such as phosphines and CO, readily coordinate to the thiametallacycle having a bimetallic core to afford the corresponding mononuclear C–S chelating thiolato complexes. The thiolato moiety is alkylated with electrophilic organic halides, including methyl iodide, benzyl bromide, and allyl halides, to yield the corresponding mononuclear thioether complexes in a stereoselective manner that validates the nucleophilic character of the coordinating sulfur atom on the thiairidacycle. By treatment of the dinuclear complex with alkynes, the carbon–carbon triple bonds insert into the thiolato–metal bond selectively to give the corresponding tridentate thioether complexes having a metal–sulfur bond. The insertion of unsymmetrical acetylenecarboxylates provides regioselective adducts where the ester substituent attaches to a carbon bound to the metal center, implying that the nucleophilic sulfur atom attacks the electrophilic β-carbon on the unsaturated ester.
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