Wow. Wow, wow, wow. I was only vaguely aware that there were organometallic compounds containing quintuple bonds. They do exist, sure, but is there anything synthetically sound you can use them for?
I just came across this article in Chemistry World. A very recent paper of Kempe’s group (Universität Bayreuth, Germany) in Chem. Commun. shows some potentially interesting application for these somewhat exotic highly bonded complexes. They can activate small stable molecules such as CO2 and SO2… Great! But how can you make this quintuple-bonded wonder?
The answer lies in a previous paper of the group in Nature Chem. and it will seem odd to many readers I guess… you have to mix the Cr(II) precursor with two equivalents of KC8, a very powerful reducing agent used in inorganic chemistry (i’ts basically a potassium-graphite mixture). So far, not too practical for synthetic applications, but later maybe… we’ll have to wait for new developments.