Metallacycle

In organometallic chemistry, a metallacycle is a derivative of a carbocyclic compound wherein a metal has replaced at least one carbon center;[2][3] this is to some extent similar to heterocycles.

In organic synthesis, directed ortho metalation is widely used for the functionalization of arene rings via C-H activation.

Most arise from the coupling of two alkynes at a low valent metal centers such as derivatives of Co(I) and Zr(II).

Late metal derivatives (Co, Ni) are intermediates in the metal-catalysed trimerization of alkynes to arenes.

They can be viewed as derivatives of benzene wherein a CH center has been replaced by a transition metal complex.

[11] Metallacyclopentanes are invoked as intermediates in the evolution of heterogeneous alkene metathesis catalysts from ethylene and metal oxides.

An early example is the cyclization of IrCl(PPh3)3 to give the corresponding Ir(III) hydride containing a four-membered IrPCC ring.

Structure of the platinacyclobutane complex PtC 3 H 6 ( bipy ) derived from activation of cyclopropane. [ 1 ]
Structure of a carbocycle ( cyclopentane ), a metallacycle (a metallacyclopentane), and a metal chelated to ethylenediamine, a metal-containing ring that is not classified as a metallacycle
Representative metallacycles. From the left: a ferrole , a cobaltacyclopentadiene (a trapped intermediate from alkyne trimerization), zirconacyclopentadiene, chromacycloheptane (intermediate in trimerization of ethylene , L is unspecified), a molybdacyclobutane, a platinacyclopentane, and an osmabenzene
The Chauvin mechanism for olefin metathesis
Structure of a palladacycle . [ 13 ]