Metallacyclopentanes

In organometallic chemistry, metallacyclopentanes are compounds with the formula LnM(CH2)4 (Ln = ligands, and M = metal).

Traditionally, metallacyclopentanes are prepared by dialkylation of metal dihalides with 1,4‐bis(bromomagnesio)butane or the related dilithio reagent.

[1] Metallacyclopentanes also arise via the dimerization of ethylene within the coordination sphere of a low-valence metal center.

[6] In the evolution of heterogeneous alkene metathesis catalysts, metallacyclopentanes are invoked as intermediates in the formation of metal alkylidenes from ethylene.

Thus, metallacyclopentane intermediates are proposed to isomerize to metallacyclobutanes, which can eliminate alkene giving the alkylidene.

Structure of the nickelacyclopentane Ni(bipyridine)(CH ₂ ) ₄ . ^{[

1

]}