Dibenzothiophene Ligand Research Articles

A metal-organic polyhedron based on dibenzothiophene ligand: Gas adsorption and reductive properties

A new metal–organic polyhedron Cu-MOP with octahedral geometry was constructed by 2,8-dibenzothiophenedicarboxylic acid and dicopper paddlewheel. Cu-MOP exhibited H2 and CO2 sorption behavior. Furthermore, Cu-MOP revealed reductive properties towards TCNQ, DDQ, CR and MB due to the electron-donating nature of DBT ligand.

A new approach to the stabilization of dibenzothiophene (DBT) coordination to metals: Studies of (η 5-C 5H 4CH 2Ph)Ru(CO) 2(η 1(S)-DBT) +

One approach to the removal of sulfur-containing compounds from transportation fuels involves the coordination of such compounds to transition metal complexes. We report the design and synthesis of a complex (η 5-C 5H 4CH 2Ph)Ru(CO) 2(η 1(S)-DBT) + that tests the concept that DBT binding through the sulfur can be augmented by π–π stacking interactions between a pendant phenyl group on the cyclopentadienyl ring and the DBT ligand. The crystal structure and kinetic binding studies of (η 5-C 5H 4CH 2Ph)Ru(CO) 2(DBT) + are reported and discussed.

Synthetic, Structural, and Kinetic Studies of [CpRu(CO)2(μ2-η1(S):η6-DBT)RuCp*][PF6]2: A Dibenzothiophene Bridge between Two Ruthenium Fragments

The complexes [CpRu(CO)2(μ2-η1(S):η6-DBT)RuCp‘]2+ (Cp‘ = η5-C5H5 (3), η5-C5Me5 (4)) were synthesized and shown by X-ray crystallography to contain a bridging dibenzothiophene ligand that is coordinated to {CpRu(CO)2}+ through the sulfur atom and to {Cp‘Ru}+ through an arene ring (η6). Kinetic studies of the displacement of the [Cp*Ru(η6-DBT)]+ moiety in 4 by P(OPh)3 show that the η6-coordinated {Cp*Ru}+ group weakens the Ru−S bond, as compared to that in [CpRu(CO)2(η1(S)-DBT)]+, and greatly increases the rate of DBT dissociation.

Synthetic, structural and binding studies of the 4,6-dimethyldibenzothiophene complex [(eta(5)-C(5)Me(5))Ru(CO)(2)(eta(1)(S)-4,6-Me(2)DBT)]BF(4): toward an understanding of deep hydrodesulfurization.

The synthesis of the first completely characterized transition-metal complex containing a sulfur-bound 4,6-dimethyldibenzothiophene (4,6-Me(2)DBT) ligand, [CpRu(CO)(2)(eta(1)(S)-4,6-Me(2)DBT)]BF(4) (1) (Cp = eta(5)-C(5)Me(5)), is reported. X-ray studies of 1 and its 4-methyldibenzothiophene and dibenzothiophene analogues, [CpRu(CO)(2)(eta(1)(S)-4-MeDBT)]BF(4) (2) and [CpRu(CO)(2)(eta(1)(S)-DBT)]BF(4) (3), show that the Ru-S bond distances increase in the order, 3 < 2 < 1. Equilibrium studies on the series of [CpRu(CO)(2)(eta(1)(S)-DBTh)](+) compounds, where DBTh = DBT, 4-MeDBT, 4,6-Me(2)DBT, and 2,8-Me(2)DBT, show that the relative binding strengths of the dibenzothiophene ligands increase in the order 4,6-Me(2)DBT (1) < 4-MeDBT (20.2(1)) < DBT (62.7(6)) < 2,8-Me(2)DBT (223(3)). These results are the first to quantify the steric effect of 4- and 6-methyl groups on the sulfur-coordinating ability of dibenzothiophenes to transition-metal centers. They are also consistent with the proposal that 4- and 6-methyl groups reduce the coordination of dibenzothiophenes to active metal sites on hydrodesulfurization catalysts, which could account for the slow rate of 4-MeDBT and 4,6-Me(2)DBT hydrodesulfurization in petroleum feedstocks.

Re2(CO)10-Mediated Carbon−Hydrogen and Carbon−Sulfur Bond Cleavage of Dibenzothiophene and 2,5-Dimethylthiophene

Ultraviolet photolysis of Re2(CO)10 and excess dibenzothiophene (DBT) in the noncoordinating solvent hexanes produces the S-bound eq-Re2(CO)9(η1(S)-DBT) (1) and the novel C−H-cleaved DBT complex Re2(CO)8(μ-C12H7S)(μ-H) (2). Under similar conditions, Re2(CO)10 reacts with excess 2,5-dimethylthiophene (2,5-Me2T) to give the interesting C−S-cleaved 2,5-Me2T complex Re2(CO)7(μ-2,5-Me2T) (3). The photolysis reactions of Re2(CO)10 with DBT and 2,5-Me2T were inhibited by CO (1 atm) and also by the radical scavenger TEMPO, which suggests that both CO dissociation and homolytic Re−Re bond cleavage are involved. The η1(S)-bound thiophene complexes 1 and Re2(CO)9(η1(S)-2,5-Me2T) (5) were prepared from Re2(CO)9(THF) (4). The DBT ligand in 1 is labile and rapidly (<2 min) reacts with CO (1 atm) to form Re2(CO)10 in 1,2-DCE. On the basis of its X-ray structure, complex 1 has one of the smallest tilt angles (θ = 113°) observed for a metal−thiophene complex, which may be understood in terms of π-back-bonding arguments. Complexes 1−3 were characterized by spectroscopic (IR, NMR) methods and by their structures that were determined by X-ray crystallography. Mechanisms for the formation of 1−3 are presented and discussed.

Transition Metal Complexes of Chromium, Molybdenum, Tungsten, and Manganese Containing η1(S)-2,5-Dimethylthiophene, Benzothiophene, and Dibenzothiophene Ligands

Ultraviolet photolysis of hexanes solutions containing the complexes M(CO)6 (M = Cr, Mo, W) or CpMn(CO)3 (Cp = η5-C5H5) and excess thiophene (T*) (T* = 2,5-dimethylthiophene (2,5-Me2T), benzothiophene (BT), or dibenzothiophene (DBT)) produces the η1(S)-T* complexes (CO)5M(η1(S)-T*) 1−8 or Cp(CO)2Mn(η1(S)-T*) 9−11, respectively. However, when T* = DBT and M = Mo, a mixture of two products results, which includes (CO)5Mo(η1(S)-DBT), 4a, and the π-complex (CO)3Mo(η6-DBT), 4b, as detected by 1H NMR spectroscopy. Only the complexes (CO)5W(η1(S)-DBT) (1), (CO)5Cr(η1(S)-DBT) (5), and Cp(CO)2Mn(η1(S)-DBT) (9) were sufficiently stable (several days) to be isolated and characterized by elemental analyses. Rates of DBT ligand displacement by CO (1 atm) at room temperature decreased in the order 5 > 1 > 9. Single-crystal, X-ray structural determinations are reported for 1, 5, and 9. The tilt angle (θ) of the DBT ligand in these and related complexes is discussed in terms of π-back-bonding to the DBT ligand.

Synthesis and structure of a stable complex featuring an S-bound dibenzothiophene ligand: RuCl2(4-R2PDBT)2 (DBT = dibenzothiophene)

Synthesis and structure of a stable complex featuring an S-bound dibenzothiophene ligand: RuCl2(4-R2PDBT)2 (DBT = dibenzothiophene)