Methylidynetricobaltnonacarbonyl is an organometallic cobalt cluster with the chemical formula Co3(CO)9CH that contains a metal carbonyl core with the methylidyne ligand, first discovered in the late 1950s.

A variety of substituents can be added to the methylidyne group to form derivatives of the parent compound that have unique spectroscopic properties and reactivity.

This page will explore the discovery and synthesis of methylidynetricobaltnonacarbonyl, the structure and bonding of the parent compound, as well as some examples reactivity and catalysis with the cluster.

[2] The synthetic procedure developed by Bor and coworkers relied on the reaction of [Co(CO)4]− anion with chloroform, bromoform, or iodoform in a solution of acetone or THF.

The Co-C-Co angle is approximately 80°, indicating a significant bending of the carbon tetrahedral structure, and the ligands are arranged to provide maximum cobalt-carbon interaction.

[8] The group concluded the exchange rate of the carbonyl ligands decreases according to the order F > Cl > Br > H, which they attributed to the electronegativity of the atom bound to the methylidyne carbon.

The order of initiator activity was found to be X = Cl > H > Br > Ph > F > i-Pr > C2F5, which aligns with the trend seen for CO ligand exchange studies.