Heterogeneous catalysis of the hydrodesulfurization of thiophenes in petroleum: an organometallic perspective of the mechanism

Preparations for 1,4,7,11,14,17-hexa-thiacycloeicosane, 1,4,7-trithiecan-9-ol, 1,11 -dioxa-4,8,14,18-tetrathia-cycloeicosane, 1 -oxa-4,8-dithiacyclo-decane, and some complexes of iron, cobalt, nickel, and palladium

“…Compared to crown ethers, the sulfur analogues have been shown to exhibit markedly different conformational preferences (5) and to produce complexes with unusual properties (7)(8)(9)(10). For example, they stabilize less common oxidation states such as Pd(III), Au(II), or Rh(I1) (9,11,12), unusual coordination geometries (13,14), and they have a large nephelauxetic effect (15,16) that leads to low-spin complexes in coordination geometries or with specific metal ions where low-spin cases are rarely encountered. Likewise, rapid electron exchange kinetics have been measured for these complexes and have been attributed to the unique structural and electronic features of the ligands (17)(18)(19).…”

Syntheses and Fluxional Processes of Diphenyl(2‐thienyl)phosphane Derivatives of Triosmium Clusters

“…The hydrido ligand which, as expected, is bridging the longest edge of the cluster, was located directly in the electron-density map. In both molecules, the hydrido ligand is on the same side of the Os 3 plane as the µ 3 -Ph 2 P(C 4 [40] and mass spectrometric and microanalytical data are consistent with the proposed formula. The variable-temperature 1 H and 31 P{ 1 H} NMR spectra of 6 demonstrate that this complex is highly fluxional.…”

“…[8,9] Rauchfuss and co-workers [10] demonstrated shortly after, that thiaferroles are easily converted into the corresponding ferroles on heating and thereby established that insertion of an iron atom into a C-S bond clearly activates the heterocycle towards desulfurisation [Scheme 1(a)]. Similarly, the reaction of [Ru 3 (CO) 12 ] with thiophene proceeds through C-S bond cleavage, producing the sulfur-free ferrole-type compound [Ru 2 (µ-C 4 H 4 )(CO) 6 ] and the tetranuclear cluster [Ru 4 (µ 3 -S)(µ-C 4 H 4 )(CO) 11 ]; [11] this is the first reported example of desulfurisation of a thiophene in which both the extruded sulfur and the hydrocarbon residue remain coordinated within the same complex [Scheme 1(b)]. More recently, Angelici and co-workers [12] have demonstrated [Re 2 (CO) 10 ]-promoted C-S bond cleavage in benzothiophenes.…”

C–S Bond Activation and Partial Hydrogenation of Thiophene by a Dinuclear Trihydride Platinum Complex

“…[1][2][3][4][5][6] This is a step in industrial oil refining in which sulfur is removed from crude oil by being chemically converted to H 2 S and hydrocarbon products. [7,8] Conventionally, the HDS process involves a reaction with hydrogen gas (up to 200 atm pressure) at temperatures of 300-450°C over an alumina supported cobalt (or nickel) molybdenum catalyst.…”

“…The evident importance of HDS together with environmental regulations that dictate increasingly smaller amounts of sulfur in gasoline and gasoil fuels [9,10] account for the current interest in developing more efficient technologies. Several reviews of the results obtained in the search for new heterogeneous catalysts, [11][12][13][14][15] in homogeneous modeling studies with transition-metal complexes [1,2,4,[16][17][18] and in computational stud- ies dealing with several aspects of heterogeneous HDS, [19][20][21][22][23] have already appeared. Remarkably, despite the large number of studies, the mechanism for the heterogeneous HDS of thiophenic molecules is not completely known and current technology has been unsuccessful in treating these compounds to achieve the sulfur levels required by new legislation.…”