C. Bianchini et al., 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), Organometallics, 14(10), 1995, pp. 4850-4857
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 bon
d 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 th
an 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 thioet
her complex [(triphos)IrH(MeSC(12)H(8))]BPh(4) (5). Treatment of 1 wit
h a strong protic acid results in the formation of the mu-thiolate dim
er [(triphos)IrH(mu-SC12H9)(2)HIr(triphos)]BPh(4))(2) (8). Deuterium l
abeling experiments exclude the proposition that the proton attacks th
e terminal hydride ligand in 1. A mechanism is proposed which involves
attack by H+ at the sulfur atom, followed by proton transfer to the m
etalated carbon atom; The dimer 8 reacts with CO to give either 4 (1 a
tm, 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 carbonylati
on (5 atm of CO, greater than or equal to 60 degrees C) or hydrogenati
on (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 (tri
phos)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 infor
mation on the heterogeneous hydrodesulfurization (HDS) of DBT.