A rhenium compound acting as both reductant and ligand was used to make the first linear, tetrametallic molecule with a Zn-Zn core. image: Trevor D. Lohrey

Zinc-zinc bonds are rare in chemistry. So are linear four-metal compounds. Nevertheless, Trevor D. Lohrey, a member of John Arnold’s group at the University of California, Berkeley, has made the first molecule with a Re-Zn-Zn-Re core (J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.8b12494).

Lohrey used a rhenium(I) salt to reduce ZnCl2 and make a zinc cation to which anionic rhenium compounds coordinated. Arnold says he and UC Berkeley collaborator Robert G. Bergman were shocked when they saw the molecule’s zinc dimer flanked by two other metals. The researchers determined that the Re-Zn interactions are dative, with rhenium donating a pair of electrons to an unoccupied zinc orbital. A crystal structure shows the four metal atoms are arranged in a nearly straight line. While Arnold describes the work as a “very fundamental investigation,” Lohrey says they are exploring how the rhenium reductant used in the synthesis behaves with various metals to see if they can make other unique compounds. And because it is a strong reductant, he thinks the compound may be useful for reducing otherwise inert molecules.

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