text: In the area of metal carbonyl clusters, a prototypical octahedral cluster is [FeC(CO)], which is obtained by heating iron pentacarbonyl with sodium.  Some of the CO ligands are bridging and many are terminal.  A carbide ligand resides at the center of the cluster.  A variety of analogous compounds have been reported where some or all of the Fe centres are replaced by Ru, Mn and other metals.
  Outside of carbonyl clusters, gold forms octahedral clusters.