Generation and biomimetic chemistry of tungsten-dithiolene complexes containing the hydrotris(3,5-dimethylpyrazol-1-yl)borate ligand.
Reactions of bis(thio)-W(VI) complexes, LWS2X (L = hydrotris (3,5-dimethylpyrazol-1-yl)borate, X = monoanion), with alkynes produce dithiolene complexes, LWX(dithiolene). The synthesis and characterization of orange LW(OPh){S2C2(CO2Me)2} (1) and burgundyred LW(SePh) {S2C2(Ph)(2-quinoxalinyl)} (2) and the X-ray crystal structure of 1.0.5CH2Cl2, are described in detail. Crystals of 1.0.5CH2Cl2 are orthorhombic, space group Pbcn, with a = 29.826(6), b = 13.291(4), c = 16.078(4) A, V = 6373(5) A3, and Z = 8. The six-coordinate, distorted-octahedral complex features a tridentate L ligand, a monodentate phenoxide ligand, and a bidentate dithiolene ligand. The short W-S bonds (2.267(4) and 2.279(4) A) and the parameters associated with the phenoxide ligand (W-O = 1.850(8) A, W-O-C = 146(1) degree), point to a considerable degree of W-ligand multiple bonding in the [W(OPh)(dithiolene)]+ unit. For 2, W-Se and average W-S distances of 2.49(2) A and 2.30(2) A, respectively, have been obtained from EXAFS studies. The formation of yellow 3,3'-dithiobis[2-(phenyl)thieno[2,3-b]quinoxaline] (3) upon oxidation of 2 supports the likely generation of urothione upon oxidative degradation of molybdopterin-containing tungsten enzymes from hyperthermophilic organisms.
Eagle
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AA
School of Chemistry, University of Melbourne, Parkville, Vic., Australia.
George
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GN
Tiekink
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Young
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CG
D001888:Boric Acids / Q000138:chemical synthesis / Q000737:chemistry; D003067:Coenzymes; D018360:Crystallography, X-Ray; D008024:Ligands; D008667:Metalloproteins / Q000138:chemical synthesis / Q000737:chemistry*; D000090006:Molybdenum Cofactors; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D011621:Pteridines / Q000138:chemical synthesis / Q000737:chemistry*; D014414:Tungsten / Q000737:chemistry*
D001888:Boric Acids; D003067:Coenzymes; D008024:Ligands; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D009942:Organometallic Compounds; D011621:Pteridines; D014414:Tungsten; C022261:molybdopterin