Alkylidene Generation by Chemical Routes

In these reactions, an alkylation of the metal is first proposed, followed by hydrogen abstraction in order to produce the alkylidene moiety. This is 

When [WClgj and Sn(CH3)4 or LiCH3 are used for disproportionation of 2-alkenes at low olefin/W ratios, significant amounts of 1-alkenes corresponding to the combination of CH2 with the appropriate alkylidene derivative of the olefin are obtained, together with large amounts of methane and ethane. 

A system containing [Mo(NO)2Cl2(PPh3)2] and Al2(CH3)3Cl3 as catalyst gives in 2,8-decadiene metathesis an initial burst of propene, the formation of which is explained by the following sequence [46]  

Good evidence for this mechanism has been obtained by the reversible interconversion of methyl and methylene ligands in tungsten complexes as well tantalum complexes such as [Ta(=CH Bu)(CH Bu)3] and [Ta( CH2)(CH3)( 17-05115)2]. These tantalum complexes have been prepared by a route which probably involves hydrogen abstraction. 

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