Formation Without Alkyl-Containing Cocatalysts

CARBENE FORMATION WITHOUT ALKYL CONTAINING COCATALYST 

The mechanism of alkylidene formation and thus chain initiation, in systems that contain no alkyl ligands either on the metal or cocatalyst still remains unknown. 

This situation is particularly relevant to most heterogeneous catalysts. In these cases, the initial carbene can only be formed from the olefin and the inorganic catalyst. M. L. H. Green et al. [48] have found that nucleophilic attack by (NaBH4) on ]W(j -C3H5) (jy- 5115)2][PFg] at the central carbon atom of the allyl group affords the metallacyclobutane  

This complex gives cyclopropane, and propene on heating, but upon irradiation ethylene and some methane is evolved  

However, this mechanism could not be extended to, for example, norbor-nene where // -allyl formation is not possible. Another possible mechanism is the direct, reversible conversion of a coordinated olefin to a carbene in one step via a 1,2 hydride shift [49]. 

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CARBENE FORMATION WITHOUT ALKYL CONTAINING COCATALYST... 

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