Oxidation State Of Copper Ion

The Science & Technology Concentrate “Crystal Structure of a Cuprate-Carbonyl π-Complex” states, “Bonding between a copper ion and the π-orbitals of a double bond, C=O in this case, has been observed by X-ray crystallography for the first time” (C&EN, Aug. 26, page 24).

It would have been helpful to the reader if the oxidation state of the copper ion had been specified in the above sentence. But more important, while this statement may be true for C=O bonds, it is probably not true for double bonds in general. For example, Rasika Dias’s group at the University of Texas, Arlington, has published crystal structures of some gorgeous compounds containing a copper(I) center attached to ethylene, the canonical double-bonded molecule (Organometallics 2012, DOI: 10.1021/om300567v, and references therein).

Tim Royappa
Pensacola, Fla.