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Cluster-mediated alkenyl isomerism and carbon-carbon bond formation: The reaction of the unsaturated benzothiazole cluster [Os-3(CO)(9)(mu(3)-C7H4NS)(mu-H)] with dimethyl acetylenedicarboxylate

Uddin, KM; Ghosh, S; Raha, AK; Hogarth, G; Rosenberg, E; Sharmin, A; ... Kabir, SE; + view all (2010) Cluster-mediated alkenyl isomerism and carbon-carbon bond formation: The reaction of the unsaturated benzothiazole cluster [Os-3(CO)(9)(mu(3)-C7H4NS)(mu-H)] with dimethyl acetylenedicarboxylate. J ORGANOMET CHEM , 695 (10-11) 1435 - 1440. 10.1016/j.jorganchem.2010.02.024.

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Abstract

Upon mild heating (60-65 degrees C), electron-deficient [Os-3(CO)(9)(mu(3)-C7H4NS)(mu-H)] (1) readily adds to the activated alkyne, RC CR (R = CO2Me), to give two isomers of the alkenyl complexes, [Os-3(CO)(9)(mu C7H4NS)(mu(3)-RCCHR)] (2 and 3), differing in the orientation of the benzothiazole ligand. In both the alkenyl ligand acts as a five-electron donor binding through both carbons and one of the oxygen atoms of the substituents, which adopt a relative cis disposition. Heating 2 cleanly affords 3 suggesting that the former is the kinetic product and the latter is thermodynamically favoured. At higher temperatures (110 degrees C), 3 rearranges to a third isomer [Os-3(CO)(9)(mu-C7H4NS)(mu-RCCHR)] (4) which differs in the binding mode of the alkenyl ligand and where the alkyne substituents are in a relative trans disposition. A second product of this reaction is [Os-3(CO)(8)(mu-OCH3){mu(3)-C7H4NSC(R)C}(mu-H)] (5) which results from the loss of two moles of CO, carbon-carbon coupling between hydrocarbyl and benzothiazole ligands and carbon-hydrogen addition to the triosmium centre. All new clusters are characterized by a total of 50 valence electrons and contain two metal-metal bonds as shown by single crystal X-ray diffraction studies. (C) 2010 Elsevier B. V. All rights reserved.

Type:Article
Title:Cluster-mediated alkenyl isomerism and carbon-carbon bond formation: The reaction of the unsaturated benzothiazole cluster [Os-3(CO)(9)(mu(3)-C7H4NS)(mu-H)] with dimethyl acetylenedicarboxylate
DOI:10.1016/j.jorganchem.2010.02.024
Keywords:Osmium, Carbonyl, Alkenyl isomerism, Carbon-carbon bond formation, X-ray structures, TRIOSMIUM CLUSTER, CRYSTAL-STRUCTURE, DIAZOMETHANE, ISOMERIZATION, H2OS3(CO)10, REDUCTION, CHEMISTRY, HYDROGEN, HYDRIDES, ALKYNES
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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