A. MELI’s research while affiliated with National Institute of Optics and other places

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The thermally generated 16-electron fragments [(triphos)RhH] and [(triphos)IrH] react with benzo[b]thiophene (BT) and dibenzo[b,d]thiophene (DBT) by C-S bond scission to give (triphos)Rh[η3-S(C6H4)CH=CH2] and (triphos)IrH(η2-C,S-DBT), respectively [triphos = MeC(CH2PPh2)3]- The Rh complex is an efficient catalyst precursor for the homogeneous hydrogenation of BT, forming 2-ethylthiophenol and, to a lesser extent, dihydrobenzo[b]thiophene. The Ir complex is a catalyst precursor for the homogeneous hydrogenation and hydrodesulfurization of DBT to 2-phenylthiophenol, biphenyl and H2S. The mechanisms of these catalytic transformations have been elucidated by the isolation and characterization of key species related to catalysis combined with high pressure NMR spectroscopic studies.

The coordinatively unsaturated Rh(III) catecholate complex (III) undergoes electron-transfer reactions involving the oxidation states (I)-(III) for the metal and the catecholate, semiquinone and quinone oxidation levels of the quinoid ligands.

Regioselective formation of 2-(benzoyloxy)propene (III) results from the addition of benzoic acid (I) to propyne (II) in the presence of the trigonal-bipyramidal Rh(I) monohydrides LRhH (L: E(CH2CH2PPh2)3, E: P, N).

III) (Pb21a, Z=4) is the starting compound to prepare a number of ethylene complexes of Rh containing hydride or σ-organyl coligands.

The vinylidene complexes (II) react with nucleophiles such as NEt3, MeLi, or PhLi via deprotonation to restore the parent σ-acetylide compounds.