Evidence of initiating species in systems with non-carbene catalysts

7 Evidence of initiating species in systems with non-carbene catalysts 

With every non-carbene catalyst system there is the question as to the nature of the initiating metal carbene complex and how it is formed from the catalyst/cocatalyst/ (substrate olefin). When the cocatalyst contains an alkyl group, there is usually an obvious path whereby this becomes the source of the alkylidene group attached to the metal and there is much evidence from the initial products of reaction or from end groups in polymers formed by ROMP that can be brought to bear on this question. 

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