Chromium Quintuple Bond

First discovered in 2005, Chromium, Molybdenum, Tungsten, and Rhenium, all have a special ability to form a quintuple bond; also known as a five fold bond. In Chromium cases, di-chromium was discovered to have a quintuple bond, which means that 10 electrons are participating in the bond with metal - metal. Chromium uses terphenyl ligand to perform this action, thus making it relatively weak, but stable up to 200°C. A quintuple bond is only possible if chromium atom has only one other ligand in order to keep the bond stable. Although the discovery is fairly recent, it has already provided great insight as to how transition metals are able to bond with each other.