Gold Scorpionates Capture Ethylene

Transition metal-ethylene complexes, known for nearly 200 years, were first made famous by Zeise's salt, K[PtCl₃(C₂H₄)]•H₂O, a once-mysterious complex in which an ethylene molecule binds side-on to the platinum atom. Ethylene adducts of the coinage metals copper, silver, and especially gold are still rare. H. V. Rasika Dias and Jiang Wu of the University of Texas, Arlington, now report two stable gold(I)-ethylene complexes and the first X-ray crystal structures for gold-ethylene complexes (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200703328). The complexes (shown) were made possible by using stabilizing tris(pyrazolyl)borate ligands. These ligands commonly are known as scorpionates because two of the pyrazolyl rings latch on to the metal like a scorpion's claws and the third ring arches over the metal like a scorpion's tail. This confining ligand leaves one side of the metal open for interaction with ethylene. The researchers are studying the ligand-exchange chemistry of the new complexes and their potential for catalysis, Dias says.