The synthesis of zirconacycles and further elaborations to produce a wide variety of carbocyclic and heterocyclic systems is well established. This thesis focuses on the insertion of chloro(aryl)methyllithiums (benzyl carbenoids) into a range of zirconacyclopentenes and zirconacyclopentanes. Benzyl carbenoid insertion into a zirconacyclopentene generated the zirconacyclohexene via a 1,2-metalate rearrangement. A low temperature quench afforded the expected benzyl inserted product. Quenching at higher temperatures afforded a styrene containing product. It was proposed that the styrene product was formed via a novel endocyclic cyclometallation to afford a zirconocene n2-alkene complex followed by decomplexation. A wide variety of zirconacyclopentenes and benzyl carbenoids have been investigated. A range of benzyl carbenoids were inserted into a zirconacyclopentane to afford the expected benzyl inserted product. Double benzyl carbenoid insertion was also observed and afforded a mono-alkene product. It was speculated that the bis-inserted products were formed via a zirconacycloheptane followed by a novel endocyclic cyclometallation. Having shown that zirconacyclohexenes underwent an endocyclic cyclometallation to afford a zirconocene n2-alkene complex, the concept of intramolecular trapping of the zirconocene n2-alkene complex, to generated bicyclic compounds, was investigated.