Role of single-site catalysts in the hydrogenation of thiophenes: from models systems to effective HDS catalysts

Iridium-mediated C–S bond activation and transformation: organoiridium(iii) thioether, thiolato, sulfinato and thiyl radical compounds. Synthesis, mechanistic, spectral, electrochemical and theoretical aspects

The iridium-mediated C–S bond scission by an uncommon SET reductive process: exploration of S-centered reactivity of iridium(iii) thiolato complex.

Asymmetric hydrogenation of thiophenes and benzothiophenes

An efficient and highly asymmetric ruthenium-N-heterocyclic carbene-catalyzed hydrogenation of substituted thiophenes and benzothiophenes is described, providing a new strategy for the formation of valuable enantiomerically pure tetrahydrothiophenes and 2,3-dihydrobenzothiophenes.

Platinum complexes of eta2-thiophenes

Two novel ligands, 3,4-bis(quinolin-8-yl)thiophene and 3,4-bis[6-(trifluoromethoxyl)quinolin-8-yl]thiophene, and their corresponding diplatinum complexes have been synthesized and fully characterized. These two complexes feature the inverse sandwich structures and the eta(2)-C,C thiophenes on platinum centers.

Reactivity of Mo(PMe3)6 towards benzothiophene and selenophenes: new pathways relevant to hydrodesulfurization

Mo(PMe(3))(6) cleaves a C-S bond of benzothiophene to give (kappa(2)-CHCHC(6)H(4)S)Mo(PMe(3))(4), which rapidly isomerizes to the olefin-thiophenolate and 1-metallacyclopropene-thiophenolate complexes, (kappa(1),eta(2)-CH(2)CHC(6)H(4)S)Mo(PMe(3))(3)(eta(2)-CH(2)PMe(2)) and (kappa(1),eta(2)-CH(2)CC(6)H(4)S)Mo(PMe(3))(4). The latter two molecules result from a series of hydrogen transfers and are differentiated according to whether the termini of the organic fragments coordinate as olefin or eta(2)-vinyl ligands, respectively. The reactions between Mo(PMe(3))(6) and selenophenes proceed differently from those of the corresponding thiophenes. For example, whereas Mo(PMe(3))(6) reacts with thiophene to give eta(5)-thiophene and butadiene-thiolate complexes, (eta(5)-C(4)H(4)S)Mo(PMe(3))(3) and (eta(5)-C(4)H(5)S)Mo(PMe(3))(2)(eta(2)-CH(2)PMe(2)), selenophene affords the metallacyclopentadiene complex [(kappa(2)-C(4)H(4))Mo(PMe(3))(3)(Se)](2)[Mo(PMe(3))(4)] in which the selenium has been completely abstracted from the selenophene moiety. Likewise, in addition to (kappa(1),eta(2)-CH(2)CC(6)H(4)Se)Mo(PMe(3))(4) and (kappa(1),eta(2)-CH(2)CHC(6)H(4)Se)Mo(PMe(3))(3)(eta(2)-CH(2)PMe(2)), which are counterparts of the species observed in the benzothiophene reaction, the reaction of Mo(PMe(3))(6) with benzoselenophene yields products resulting from C-C coupling, namely [kappa(2),eta(4)-Se(C(6)H(4))(CH)(4)(C(6)H(4))Se]Mo(PMe(3))(2) and [mu-Se(C(6)H(4))(CH)C(CH)(2)(C(6)H(4))](mu-Se)[Mo(PMe(3))(2)][Mo(PMe(3))(2)H].

Reactivity and catalytic activity of a robust ruthenium(II)-triphos complex

The ruthenium(II)-triphos acetato complex [RuCl(OAc)(kappa3-triphos)] (triphos = (PPh2CH2)3CMe) has been found to be an active catalyst precursor for the hydrogenation of 1-alkenes under relatively mild conditions (5-50 bar H2, 50 degrees C). In contrast to related triphenylphosphine complexes, [RuCl(OAc)(kappa3-triphos)] is much less air sensitive and high catalytic activities were achieved when catalyst samples were prepared without exclusion of air or moisture. Substitution of the acetato ligand can be effected by treatment of acid, affording [Ru2(mu-Cl)3(kappa3-triphos)2]Cl and [RuCl(kappa3-triphos)]2(BF4)2 with aqueous HCl and [Et2OH]BF4, respectively, or by heating with dmpm in the presence of [NH4]PF6, resulting in formation of [RuCl(kappa2-dmpm)(kappa3-triphos)]PF6 (dmpm = PMe2CH2PMe2). A hydride complex, [RuHCl(kappa3-triphos)], formed by acetato-mediated heterolytic cleavage of dihydrogen is proposed as the active catalytic species. An inner-sphere, monohydride mechanism is suggested for the catalytic cycle, with chloro and triphos ligands playing a spectator role. These mechanistic proposals are consistent with reactivity studies carried out on [RuCl(OAc)(kappa3-triphos)] and [RuH(OAc)(kappa3-triphos)] and supported by a computational analysis. The solid-state structures of [RuCl(OAc)(kappa3-triphos)], [RuCl(kappa3-triphos)]2(BF4)2, and [RuCl(kappa2-dmpm)(kappa3-triphos)]PF6 have been established by X-ray diffraction.

Reactions of TpRu(CO)(NCMe)(Ph) with electron-rich olefins: examples of stoichiometric C–S, C–O and C–H bond cleavage

Stoichiometric reactions of TpRu(CO)(NCMe)(Ph) with electron-rich olefins result in metal-mediated cleavage of C-S and C-O bonds.

C–H Bond activation and C–C bond formation in the reaction of 2,5-dimethylthiophene with TpMe2Ir compounds

The bulky 2,5-dimethylthiophene (2,5-Me2T) reacts at 60 degrees C with TpMe2Ir(C2H4)2 to give a mixture of two TpMe2Ir(III) hydride products, 3 and 4, that contain in addition a thienyl (3) or a thienyl-derived ligand (4). For the generation of 3 only sp2 C-H activation is needed, but the formation of 4 requires also the activation of an sp3 C-H bond and the formation of a new C-C bond (between vinyl and thienyl fragments). In the presence of 2,5-Me2T, compound 4 reacts further to produce a complex thiophenic structure (5, characterized by X-ray methods) that derives formally from two molecules of 2,5-Me2T and a vinyl fragment. Compounds 3-5 can be readily protonated by [H(OEt2)2][BAr'4](Ar'= 3,5-C6H3(CF3)2), with initial generation of carbene ligands (in the case of 3 and 5) as a consequence of H+ attack at the beta-carbon of the Ir-thienyl unit. Free, substituted thiophenes, derived from the original 2,5-Me2T, may be isolated in this way.