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| 2. |
- Lorber, Christian, et al.
(författare)
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Kinetics of Oxygen Transfer Reactions Involving Molybdenum Dithiolene Complexes
- 1997
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Ingår i: Journal of the Chemical Society, Dalton Transactions. - : Royal Society of Chemistry (RSC). - 0300-9246 .- 1364-5447. ; :21, s. 3997-4004
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Tidskriftsartikel (refereegranskat)abstract
- Oxo transfer reactions from [MoO2(mnt)2]2– [mnt2– = 2,3-disulfanylmaleonitrile dianion (1,2-dicyanoethylenedithiolate)] to the abiological oxygen acceptors PPh3–xEtx (x = 0–3) have been studied spectrophotometrically in acetonitrile. The pseudo-first-order rate constants depend linearly on the concentration of the oxo acceptors. The sequence of reactivity is PEt3 > PEt2Ph > PEtPh2 > PPh3, reflecting the basicities of the phosphines, while the steric influence of the substituents on the phosphorus atom appears to be of minor importance. The activation entropies for the reaction with PEt3 and PPh3 are negative. These observations are in agreement with the proposal that in the intermediate the entering phosphine binds to the molybdenum complex through the oxygen ligand. Oxidation of HSO3– by [MoO2(mnt)2]2– has also been studied in acetonitrile and in acetonitrile–water mixtures. The reaction exhibits Michaelis–Menten behaviour. In CH3CN–H2O, the rate of the reaction increases as the water concentration decreases; the reacting species appears to be a product from the reaction of the molybdenum starting complex with water.
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| 3. |
- Lorber, Christian, et al.
(författare)
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Synthesis, Structures and Oxo Transfer Reactivity of bis(Dithiolene) Tungsten(IV,VI) Complexes Related to the Active Sites of Tungstoenzymes
- 1998
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 120:32, s. 8102-8112
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Tidskriftsartikel (refereegranskat)abstract
- A series of bis(dithiolene)tungsten(IV,VI) complexes derived from benzene-1,2-dithiolate (bdt) has been prepared as an synthetic approach to pterin dithiolene-bound active sites of tungstoenzymes, one example of which, a archaeal oxidoreductase, has been established crystallographically (Chan et al. Science 1995, 267, 1463). With [WIVO(bdt)2]2- (2) as the starting compound, silylation with RR'2SiCl afforded [WIV(bdt)2(OSiRR'2)]1- (4). Oxidation of 4 with Me3NO gave [WVIO(bdt)2(OSiRR'2)]1- (5), also accessible by silylation of [WVIO2(bdt)2]2- (3). Reaction of 3 or 5 with Me3SiCl resulted in [WVIO(bdt)2Cl]1- (6), from which the unstable species [WVIO(bdt)2L]1- (L = ButO-, PhS-) were generated in solution. Reductive oxo transfer of 6 with L' = P(OEt)3 or ButNC/P(OEt)3 gave [WIV(bdt)2L'2] (8 and 9). Sulfido complex [WVIS(bdt)2(OSiRR'2)]1- (12) was obtained in the reaction systems 4/(PhCH2S)2S and 5/(Me3Si)2S. Structures of [WO(SPh)4]1- and [W(bdt)3]2- and eight complexes of types 4-6, 8, 9, and 12 were determined by X-ray crystallography. Complexes 4 and 5 are tungsten analogues of the desoxo Mo(IV) and monooxo Mo(VI) states of Rhodobacter sphaeroides DMSO reductase. Six types of reactivity, including oxygen atom transfer, are recognized by the synthesis and interconversion of the set of complexes. The potential biological relevance of these complexes to the structure and function of active sites in two families of tungstoenzymes is considered (RR'2 = Me3 (4); ButMe2 (4 and 5), ButPh2 (4, 5, and 12)).
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| 4. |
- Nordlander, Ebbe, et al.
(författare)
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Iron 1994
- 1997
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Ingår i: Coordination Chemistry Reviews. - 0010-8545. ; 162, s. 345-415
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Forskningsöversikt (refereegranskat)
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| 5. |
- Nordlander, Ebbe, et al.
(författare)
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Iron 1995
- 1998
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Ingår i: Coordination Chemistry Reviews. - 0010-8545. ; 172:1, s. 3-97
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Forskningsöversikt (refereegranskat)
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| 6. |
- Thapper, Anders, et al.
(författare)
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Synthesis and Reactivity Studies of Model Complexes for Molybdopterin-Dependent Enzymes
- 2000
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Ingår i: Journal of Inorganic Biochemistry. - 1873-3344. ; 79:1-4, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- The molybdenum cofactor (Moco)-containing enzymes are divided into three classes that are named after prototypical members of each family, viz. sulfite oxidase, DMSO reductase and xanthine oxidase. Functional or structural models have been prepared for these three prototypical enzymes: (i) The complex [MoO2(mnt)2]2− (mnt2−=1,2-dicyanoethylenedithiolate) has been found to be able to oxidize hydrogen sulfite to HSO4− and is thus a functional model of sulfite oxidase. Kinetic and computational studies indicate that the reaction proceeds via attack of the substrate at one of the oxo ligands of the complex, rather than at the metal. (ii) The coordination geometries of the mono-oxo [Mo(VI)(O-Ser)(S2)2] entity (S2=dithiolene moiety of molybdopterin) found in the crystal structure of R. sphaeroides DMSO reductase and the corresponding des-oxo Mo(IV) unit have been reproduced in the complexes [M(VI)O(OSiR3)(bdt)2] and [M(VI)O(OSiR3)(bdt)2] (M=Mo,W; bdt=benzene dithiolate). (iii) A facile route has been developed for the preparation of complexes containing a cis-Mo(VI)OS molybdenum oxo, sulfido moiety similar to that detected in the oxidized form of xanthine oxidase.
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