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Ansa Compounds (ansa + compound)
Selected AbstractsSynthesis and Catalytic Applications of ansa Compounds with Cycloalkyl Moieties as Bridging Units: A Comparative StudyADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Alejandro Capapé Abstract The molybdenum and tungsten compounds (Mo{,5 -C5H4[CH(CH2)n]-,1 -CH}(CO)3) and (W{,5 -C5H4[CH(CH2)3]-,1 -CH}(CO)3) (2a, 3an=3; 2b, 3bn=4; 2c, 3cn=5; 2d, 3dn=6) were synthesized by reacting the spiro-bicyclic compounds 1a,d with the complex [M(CO)3(tach)] (M=molybdenum, tungsten; tach=1,3,5-trimethylhexahydro-1,3,5-triazine). NMR spectroscopy, as well as X-ray diffraction studies, confirm the formation of an intramolecular ansa bridge. The complexes display a good stability in the solid state (stable up to 180,°C under air, as determined by thermogravimetric studies) and are highly active catalysts at room temperature (molybdenum compounds) or above (tungsten compounds) in olefin epoxidation. In the case of cyclooctene as substrate, TOFs up to ca. 11800,h,1 are obtained. Moreover, most of the catalysts described here display a high selectivity in the epoxidation of cis - and trans -stilbene. In addition, the novel complexes were compared with previously synthesized related compounds, at least matching their catalytic performances. [source] Stable and Catalytically Highly Active ansa Compounds with Cycloalkyl Moieties as Bridging UnitsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Alejandro Capapé Abstract The complexes Mo{,5 -C5H4[CH(CH2)3]-,1 -CH}(CO)3 (2a) and W{,5 -C5H4[CH(CH2)3]-,1 -CH}CO)3 (2b) were synthesized by reacting spiro[4.2]bicyclo[4.1]deca-6,8-diene (1) with the tri(acetonitrile)tri(carbonyl)metal complexes M(CO)3(CH3CN)3 (M=Mo, W). Thermogravimetric (TGA) measurements confirm that the complexes are stable up to 140,°C in air in the solid state. The complexes 2a and 2b are very active catalysts at room temperature for the epoxidation of cyclooctene with tert -butyl hydroperoxide (TBHP) as oxidant, reaching TOFs of up to 3650,h,1. Complex 2a achieves a quantitative product yield without formation of any by-products within 1.5,h, outperforming previously published ansa compounds and performing on par with the cyclopentadienyltri(carbonyl)(halo)- or (alkyl)molybdenum compelxes CpMo(CO)3R (R=Hal, Me, Et). [source] Olefin Epoxidation with a New Class of Ansa -Molybdenum Catalysts in Ionic LiquidsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 5 2010Daniel Betz Is that a finalansa? Different room temperature ionic liquids (RTILs) are examined as solvents in the biphasic epoxidation of selected olefins with the ansa compounds 1 and 2 as catalyst precursors. Turnover frequencies of up to 44,000,h,1 are reached and the catalyst can easily be separated and recycled. [source] | ||||||||||