Diorganochromium

Organochromium chemistry is a branch of organometallic chemistry that deals with organic compounds containing a chromium to carbon bond and their reactions. The field is of some relevance to organic synthesis. The relevant oxidation states for chromium range from -2 to +6.

The first organochromium compound was described in 1919 by Franz Hein. He treated phenylmagnesium bromide with chromium(III) chloride to give a new product (after hydrolysis) which he incorrectly identified as pentaphenyl chromium bromide (Ph₅CrBr). Years later, in 1957 H.H. Zeiss et al. repeated Hein's experiments and correctly arrived at a cationic bisarene chromium sandwich compound (Ar₂Cr⁺).Bis(benzene)chromium itself was discovered around the same time in 1956 by Ernst Otto Fischer by reaction of chromium(III) chloride, benzene and aluminum chloride. The related compound chromocene was discovered a few years earlier in 1953 also by Fischer.

In another development, Anet and Leblanc also in 1957 prepared a benzyl chromium solution from benzyl bromide and chromium(II) perchlorate. This reaction involves one-electron oxidative addition of the carbon-bromine bond, a process which was shown by Kochi to be a case of double single electron transfer, first to give the benzyl free radical and then to the benzyl anion.