The Catalytic Transformation of Benzo[b]thiophene to 2-Ethylthiophenol by a Soluble Rhodium Complex: The Reaction Mechanism Involves Ring Opening Prior to Hydrogenation

The great importance of heterogeneous hydrodesulfurization (HDS)"] has spawned numerous studies with homogeneous model systems.I2] Of particular interest has been the activation of derivatives of thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT). While all three of these sulfur-containing molecules are relevant to HDS, the latter two are especially so because they are more difficult to desulfurize and thus are much more abundant in fossil fuels. The key step in HDS is cleavage of the S-C bonds, and a reasonable way for this to occur is by initial coordination to a metal followed by insertion into the S-C bond. In particular, precoordination of the metal to the sulfur atom of the thiophene unit is thought to be crucial to S-C bondIn the case of BT ( I ) , several examples of the insertion of metal fragments ML, into the have been reported ; however, there have been no reports of S-C(aryl) bond cleavage to give 3. The X-ray structurer4] of [(BT)Re(CO),Cp*] (Cp* = C,Me,), in which the rhenium S-C(viny1) bond to give 2 (M = Fe, Ru, Rh, Ir, Pt13b.5361 ) 1 2 3atom is q'-bonded to the sulfur atom. suggests that ql-S coordination selectively weakens the S-C(viny1) bond but not the S-C(ary1) bond, thus providing an explanation16e1 for why 2, and not 3, is formed. Herein we demonstrate that the insertion of a metal atom into the S-C(ary1) bond of BT to give complexes of type 3 can, in fact, be readily accomplished.

show abstract

“…MnlGC8 2.312 (5). Mnl -C9 2.301 (5). Mn2 S1 2.369(2), Mn2ZC8 2 091(6), Mn2-Cl3 1.835 (8), Mn2-Cl4 1.804 (7).…”

mentioning

confidence: 99%

Model Compounds for the Homogeneous Hydrodesulfurization of Benzothiophene: Insertion of Manganese into the SC(aryl) Bond

Dullaghan

Sun

Carpenter

et al. 1996

Angew. Chem. Int. Ed. Engl.

View full text Add to dashboard Cite

show abstract

“…Indeed, this species also forms by hydrogenation of 1 in MeOH- d 4 in the presence of KOBu t (see below) and does not react with either BT or ETP. Compounds 2 − 4 were identified by comparison of their 31 P{ 1 H} NMR spectra to those of the analogous triphos complexes [(triphos)Rh(η 3 -S(C 6 H 4 )CHCH 2 )] ( 2* ), [(triphos)Rh(H) 2 ( o -S(C 6 H 4 )C 2 H 5 )] ( 3* ),9c and [(triphos)Rh(H) 3 ] ( 4* ), respectively. Increasing the temperature to 120 °C (a temperature to which the catalysis occurs, see entry 5 in Table ) led to a considerable increase of the concentration of the thiolate dihydride 3 at the expense of both 2 and 4 .…”

Section: Methodsmentioning

confidence: 99%

“…The key role of the metal promoter in the activation of the thiophenes has also been supported by several homogeneous modeling studies which clearly show that C−S bond scission is almost exclusively brought about by promoter metal complexes . For the following, crucial desulfurization step, however, soluble metal complexes are generally inefficient, unless either W (or Mo) or hydride ligands bound to a second metallic center are comprised in the complex framework. − In the absence of these two conditions, the ultimate activation of thiophenes by soluble metal complexes seems to be the conversion to thiolate ligands, which may eventually be eliminated as thiols upon treatment with H 2 . − Homogeneous catalytic reactions for the hydrogenolysis of thiophene, benzo[ b ]thiophene, dibenzo[ b,d ]thiophene, and dinaphtho[2,1- b :1‘,2‘- d ]thiophene have already been reported. 9c,d, …”

Section: Introductionmentioning

confidence: 99%

Liquid-Biphase Hydrogenolysis of Benzo[b]thiophene by Rhodium Catalysis

Bianchini¹,

Meli²,

Patinec³

et al. 1997

J. Am. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

The catalytic activity of the zwitterionic complex [(sulphos)Rh(cod)] for the hydrogenation and hydrogenolysis reactions of benzo[b]thiophene (BT) has been studied in either methanol or liquid-biphase systems comprising MeOH or MeOH−H2O as the polar phase and n-heptane as the organic phase [sulphos = -O3S(C6H4)CH2C(CH2PPh2)3]. The catalyst activity is independent of the phase variation. Under neutral conditions, the slow but selective hydrogenation of BT to 2,3-dihydrobenzo[b]thiophene is observed. Conversely, in the presence of NaOH or other strong bases, the fast and selective hydrogenolysis of BT to 2-ethylthiophenol sodium salt occurs. In a typical liquid-biphase hydrogenolysis reaction [35 mg (0.035 mmol) of catalyst, 470 mg (3.5 mmol) of BT, 180 mg (4.5 mmol) of NaOH, 5 mL of MeOH, 5 mL of H2O, 10 mL of n-heptane, 30 bar of H2, 160 °C], all the substrate is practically consumed in ca. 5 h to give the 2-ethylthiophenolate product. The strong base plays a dual role in the hydrogenolysis reaction: it promotes the formation of the Rh−H species (which is necessary for the C−S insertion step) by heterolytic splitting of H2 and accelerates the conversion of BT by aiding the reductive elimination of the hydrogenolysis product. The effect of the H2 pressure and of the substrate, catalyst, and base concentrations on the conversion rate of BT has been studied under liquid-biphase conditions. High-pressure NMR experiments in sapphire tubes have provided mechanistic information on the catalysis cycle for the hydrogenolysis of BT in MeOH. Under catalytic conditions, the phosphorus-containing rhodium compounds (visible on the NMR time scale) are the trihydride [(sulphos)RhH3]- and the dihydride 2-ethylthiophenolate complex [(sulphos)Rh(H)2(o-S(C6H4)C2H5)]-. Consistent with previous studies, the reductive elimination of the thiol from the metal center is suggested to be the rate-determining step of the hydrogenolysis reaction of BT catalyzed by the 16e- fragment [(sulphos)RhH]-.

show abstract

“…Crude oil contains organic sulfur compounds as impurities that cause environmental pollution. Many studies1–4 have sought to desulfurize oil and coal, although it is also important to challenge the utilization of sulfur components. Dibenzothiophene derivatives have been reported5 to be the most abundant compounds in gas oil.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of novel π‐conjugating polymers based on dibenzothiophene

Nemoto

Kameshima

Okano

et al. 2003

J. Polym. Sci. A Polym. Chem.

View full text Add to dashboard Cite

Novel π‐conjugating polymers based on dibenzothiophene were synthesized with a novel dibenzothiophene derivative, 2,8‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)dibenzothiophene (1), prepared from dibenzothiophene. The Suzuki coupling polycondensation of 1 with 2,7‐dibromo‐9,9‐dioctylfluorene, 3,6‐dibromo‐9‐octylcarbazole, or 1,4‐dibromo‐2,5‐dioctyloxybenzene afforded the corresponding dibenzothiophene‐based polymers. The measurements of photoluminescence indicated that all these polymers exhibited blue emission in solution. The copolymer containing dibenzothiophene and 9,9‐dioctylfluorene units exhibited higher thermal stability than poly[(9,9‐dioctylfluorene‐2,7‐diyl)], although the quantum yield of copolymer was lower than that of poly[(9,9‐dioctylfluorene‐2,7‐diyl)]. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1521–1526, 2003

show abstract

The Catalytic Transformation of Benzo[b]thiophene to 2-Ethylthiophenol by a Soluble Rhodium Complex: The Reaction Mechanism Involves Ring Opening Prior to Hydrogenation

Cited by 70 publications

References 0 publications

Model Compounds for the Homogeneous Hydrodesulfurization of Benzothiophene: Insertion of Manganese into the SC(aryl) Bond

Model Compounds for the Homogeneous Hydrodesulfurization of Benzothiophene: Insertion of Manganese into the SC(aryl) Bond

Liquid-Biphase Hydrogenolysis of Benzo[b]thiophene by Rhodium Catalysis

Synthesis of novel π‐conjugating polymers based on dibenzothiophene

Contact Info

Product

Resources

About