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Science 4 April 1997:
Vol. 276. no. 5309, pp. 99 - 102
DOI: 10.1126/science.276.5309.99
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Reports

Metathesis of Alkanes Catalyzed by Silica-Supported Transition Metal Hydrides

Véronique Vidal, Albert Théolier, Jean Thivolle-Cazat, Jean-Marie Basset *

The silica-supported transition metal hydrides (equiv Si-O-Siequiv )(equiv Si-O-)2Ta-H and (equiv Si-O-)xM-H (M, chromium or tungsten) catalyze the metathesis reaction of linear or branched alkanes into the next higher and lower alkanes at moderate temperature (25° to 200°C). With (equiv Si-O-Siequiv )(equiv Si-O-)2Ta-H, ethane was transformed at room temperature into an equimolar mixture of propane and methane. Higher and lower homologs were obtained from propane, butane, and pentane as well as from branched alkanes such as isobutane and isopentane. The mechanism of the step leading to carbon-carbon bond cleavage and formation likely involves a four-centered transition state between a tantalum-alkyl intermediate and a carbon-carbon sigma -bond of a second molecule of alkane.

Laboratoire de Chimie Organométallique de Surface, UMR CNRS-CPE 9986, 43 Boulevard du 11 Novembre 1918, 69616 Villeurbanne Cédex, France.
*   To whom correspondence should be addressed.

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