ETUDES SUR LE MECANISME DE LA METATHESE DES OLEFINES II. COUPURE DES ALKYLTUNGSTENES, AMORCAGES ANORMAUX

Article abstract of DOI:10.1016/S0022-328X(00)81229-2

With a view to elucidating the mode of action of tungsten containing catalyst of the olefin metathesis, the thermal decomposition of various alkyltungsten derivatives was examined.It was shown that n-alkyltungsten derivatives (i.e. n-alkylmagnesium halides + WCl6) are decomposed to lighter alkenes and alkanes (i.e. propyl to ethylene, ethane and methane).With methyl or neopentyl derivatives of tungsten, alkenes are observed, which derive from alkylation and fission of the metathesis substrate (i.e.Me3CCH2MgBr + WCl6 + 2-pentene give inter alia 2,2-dimethyl-4 hexene).Metathesis of tetramethylethylene was also observed, as evidenced by the formation of 2-methyl-2-pentene in the presence of 3-hexene.All these facts agree with the intermediacy of a tungsten hydride as the key step in the formation of a metathesis catalyst, intermediacy which is linked with the formation of tungstacarbene (alkylidene tungsten).