METAL ACTIVATION OF DIBENZO[B,D]THIOPHENE - REACTIVITY OF THE C-S INSERTION PRODUCT [MEC(CH(2)PPH(2))(3)]IRH(ETA(2)(C,S)-C12H8S)

The reactivity of the Ir(III) complex (triphos)IrH(eta(2)(C,S)-DBT) (1), obtained by insertion of the [(triphos)IrH] fragment into a C-S bond of DBT, has been studied in THF [triphos = MeC(CH(2)PPh(2))(3); DBT = dibenzo[b,d]thiophene]. Compound 1 reacts with CO (5 atm, greater than or equal to 50 degrees C) to give the 2-phenylthiophenolate complex (triphos)Ir(CO)(SC12H9) (3) and with MeI/ NaBPh(4) to give the thioether complex [(triphos)IrH(MeSC(12)H(8))]BPh(4) (5). Treatment of 1 with a strong protic acid results in the formation of the mu-thiolate dimer [(triphos)IrH(mu-SC12H9)(2)HIr(triphos)]BPh(4))(2) (8). Deuterium labeling experiments exclude the proposition that the proton attacks the terminal hydride ligand in 1. A mechanism is proposed which involves attack by H+ at the sulfur atom, followed by proton transfer to the metalated carbon atom; The dimer 8 reacts with CO to give either 4 (1 atm, 20 degrees C) or the dicarbonyl complex [(triphos)Ir(Co)(2)]BPh(4) (6) plus free 2-phenylthiophenol (5 atm, greater than or equal to 70 degrees C. 2-(Methylthio)-biphenyl is obtained from either carbonylation (5 atm of CO, greater than or equal to 60 degrees C) or hydrogenation (5 atm of H-2, greater than or equal to 100 degrees C) of 5. in the latter ease, all the iridium is incorporated into the trihydride (triphos)IrH3. All the carbonylation and hydrogenation reactions have been studied in situ by high-pressure NMR (HPNMR) spectroscopy in sapphire tubes. Some of the results herein presented provide mechanistic information on the heterogeneous hydrodesulfurization (HDS) of DBT.