Bicyclo pentanes metal-catalyzed

It appears likely that transient metallacyclobutanes are involved in a variety of organic reactions which are catalyzed by transition metal complexes. Thus, cycloadditions of activated alkenes to strained hydrocarbons such as quadricyclane and bicyclo[2.1.0]pentane are catalyzed by complexes such as Ni(CH2=CHCN)2 and probably involve initial formation of a nickelacyclobutane (Scheme 2) (79MI12200). The nature of the organometallic intermediates in related metal-catalyzed rearrangements (72JA7757) and retro-cyclo-addition reactions (76JA6057) of cyclopropanoid hydrocarbons, e.g. bicyclo[n.l.O]alkanes, has been discussed. 

TRANSITION METAL CATALYZED REACTIONS OF BICYCLO[2.1.0]PENTANES SYNTHESIS OF 1186 BICYCLO[2.2.1IHEPTANES... 

Bicyclo[1.1.0]butanes, the smallest bicycloalkanes, have remarkably large strain energies (63-68 kcalmol ) and have attracted the attention of many chemists for more than half a century. The n-character of the central bond in bicyclobutane has been confirmed experimentally. In fact, treatment of bicyclobutane with Zeise s dimer and pyridine led to the formation of a platinabicyclo[l.l.l]pentane complex via cleavage of the central C1-C3 bond [19]. However, in most cases, transition-metal-catalyzed rearrangement of bicyclobutanes did not involve the initial cleavage of the central C-C bond. 

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