Synthesis, Structure, Spectroscopy, and Reactivity of a Metallathiabenzene¹

Treatment of (Cl)Ir(PEt 3 ) 3 with lithium 2,3-dimethyl-5-thiapentadienide leads to the production of ( 4 ) via C−H bond activation. Oxidation of 4 with silver tetrafluoroborate in tetrahydrofuran generates “iridathiabenzene”, ( 3 ). The structural and spectroscopic features of 3 are consistent with the presence of an aromatic ring in which the iridium center participates in ring π-bonding. Treatment of 3 with excess PMe 3 or with PPN + Cl - leads to the production of ( 5 ) or ( 6 ), respectively. Each of these products features an iridathiacyclohexa-1,3-diene ring system. The reaction of 6 with 1 / 2 equiv of silver trifluoromethanesulfonate leads to the production of a novel iridium dimer, ( 7 ), in which the two iridium centers are bridged by the two sulfur atoms of the iridathiacyclohexa-1,3-diene rings, as well as a chloride ligand. Treatment of 3 with nitrosobenzene generates a [4 + 2] cycloadduct, ( 8 ), containing an iridathiacyclohexa-1,4-diene ring. Compound 3 cleanly displaces p -xylene from (η 6 - p -xylene)Mo(CO) 3 in tetrahydrofuran, generating ( 9 ). When 9 is reacted with excess trimethylphosphine, PMe 3 adds to the molybdenum center, causing the iridathiabenzene ring to slip from η 6 to η 4 coordination and forming ( 10 ). Finally, treatment of (η 5 -C 5 Me 5 )Ru(NCMe) 3 + O 3 SCF 3 - with 3 leads to clean displacement of the acetonitrile ligands by the iridathiabenzene ring and generation of the Ru sandwich compound ( 11 ). Compounds 3, 4, 6a, 7, 9, and 10 have been structurally characterized by X-ray diffraction.