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Synthesis

Crystal Structure Of A Cuprate-Carbonyl π-Complex

Data for long-predicted intermediate in copper catalysis could aid synthetic method design

by Craig Bettenhausen
August 26, 2013 | A version of this story appeared in Volume 91, Issue 34

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The copper center of the cuprate-carbonyl π-complex adopts a pseudo-square planar geometry.
This is the crystal structure of a cuprate-carbonyl pi-complex.
The copper center of the cuprate-carbonyl π-complex adopts a pseudo-square planar geometry.

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. Such three-center bonds have been proposed as intermediates in a number of important copper-catalyzed reactions, including additions using Gilman reagents (R2CuLi). The arrangement is unstable, and until recently, researchers have only been able to infer the intermediate’s existence. In June, Steven H. Bertz, Craig A. Ogle, and Richard A. Hardin of the University of North Carolina, Charlotte, reported that by using a tetra­hydrofuran-based solvent system they could stabilize a series of cuprate-carbonyl π-complexes and record their NMR signatures (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja404105u). Now, the team has prepared one of the compounds at the gram scale and grown crystals suitable for X-ray analysis (Angew. Chem. Int. Ed. 2013, DOI: 10.1002/anie.201303783). The structure (shown) confirms structural predictions previously made on the basis of NMR and theoretical calculations. Correlating the data obtained from the X-ray and NMR methods may help chemists leverage the instability of these intermediates to tune and customize catalytic reactions.

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