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Title: Metal alkoxides. Models for metal oxides. 15. Carbon-carbon and carbon-hydrogen bond activation in the reactions between ethylene and ditungsten hexaalkoxides: W sub 2 (OCH sub 2 -t-Bu) sub 6 (. eta. sup 2 -C sub 2 H sub 4 ) sub 2 , W sub 2 (OR) sub 6 (CH sub 2 ) sub 4 (. eta. sup 2 -C sub 2 H sub 4 ), and W sub 2 (OR) sub 6 (. mu. -CCH sub 2 CH sub 2 CH sub 2 ) (where r = CH sub 2 -t-Bu, i-Pr, c-C sub 5 h sub 9 , and c-C sub 6 H sub 11 ). Preparations, properties, structures, and reaction mechanisms

Journal Article · · Journal of the American Chemical Society; (USA)
DOI:https://doi.org/10.1021/ja00196a039· OSTI ID:6946164

W{sub 2}(OR){sub 6} (M {triple bond}M) compounds and ethylene (1 atm, 22{degree}C) react in alkane and aromatic hydrocarbon solvents to give W{sub 2}(OR){sub 6}({mu}-CCH{sub 2}CH{sub 2}CH{sub 2}) compounds and ethane, where R = i-Pr, c-C{sub 5}H{sub 9}, c-C{sub 6}H{sub 11}, and CH{sub 2}-t-Bu. Under comparable conditions, W{sub 2}(O-t-Bu){sub 6} and ethylene fail to react. In the formation of W{sub 2}(OR){sub 6}({mu}-CCH{sub 2}CH{sub 2}CH{sub 2}) compounds, the intermediates W{sub 2}(OCH{sub 2}-t-Bu){sub 6}({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} and W{sub 2}(OR){sub 6}(CH{sub 2}){sub 4}({eta}{sup 2}-C{sub 2}H{sub 4}), where R = C-C{sub 5}H{sub 9}, i-Pr, and CH{sub 2}-t-Bu, have been characterized. For R = i-Pr and CH{sub 2}-t-Bu, the intermediates are shown to be formed reversibly from W{sub 2}(OR){sub 6} and ethylene. The compound W{sub 2}(O-i-Pr){sub 6}(CH{sub 2}){sub 4}({eta}{sup 2}-C{sub 2}H{sub 4}) has been fully characterized by an X-ray study and found to contain a metallacyclopentane ring and a W-{eta}{sup 2}-C{sub 2}H{sub 4} moiety, one at each metal center. The pyridine adduct W{sub 2}(O-i-Pr){sub 6}({mu}-CCH{sub 2}CH{sub 2}ch{sub 2})(py) has been fully characterized and shown to contain a novel 1,6-dimetallabicyclo(3.1.0)hex-1(5)-ene organometallic core. All compounds have been characterized by {sup 13}C and {sup 1}H NMR studies. Various aspects of the reaction pathway have been probed by the use of isotopically labeled ethylenes, and a proposed general scheme is compared to previous studies of ethylene activation at mononuclear metal centers and carbonyl dinuclear and cluster compounds.

OSTI ID:
6946164
Journal Information:
Journal of the American Chemical Society; (USA), Vol. 111:14; ISSN 0002-7863
Country of Publication:
United States
Language:
English