Catalysts without a Metal Hydrocarbyl or

3 Catalysts without a Metal Hydrocarbyl or Hydride Activator 

Metal hydride species can undergo an insertion reaction with an olefinic double bond, resulting in the formation of a metal alkyl species which then generates the requisite carbenoids by a-hydride abstraction [110-112]  

It has been found [113,114] that there are numerous sources of original hydride in various polymerisation systems. In supported catalysts, the carrier, which contains surface hydroxyl groups, can serve as the addendum. In other cases the hydride can be originated from water, alcohol or phenol if they are required for the activation [115]. 

Metallacyclobutane species (which then afford initiating carbenoids) can be formed in polymerisation systems with supported catalysts by monomer reaction via a metal re-allyl complex and metal hydride. A reaction of this type, where the olefin is 2,8-decadiene, is shown by the following scheme (R = H3CCH=CH-(CH2)4-) [116]  

In the case of polymerisation in the presence of heterogeneous catalysts with the transition metal in a low oxidation state, metallacyclobutane species can also be formed by the intentional addition of cyclopropane to the system [117]  

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