Synthesis and structure of gold(III) complexes of asymmetric dithiolene ligands

Four new [Au(dithiolene)2]− complexes, each involving two asymmetrically substituted dithiolene ligands (SC(H)C(R)S; R = phenyl, pyridin-2-yl, pyridin-3-yl, or pyridin-4-yl), have been synthesized by reacting K[AuCl4] with the corresponding dithiolene, generated by base hydrolysis of the thione-protected 1,3-dithiolate. Each complex has been isolated as its [PPh4]+ salt and the structures of these [PPh4][Au(dithiolene)2] compounds have been determined by X-ray crystallography; each anion possesses a square planar {AuS4} core with a cis-arrangement of the R groups for R = phenyl and pyridin-2-yl complexes, but a trans-arrangement for R = pyridin-3-yl and pyridin-4-yl. In each compound, the lengths of the C–C (1.34 ± 0.01 Å) and C–S (1.75 0.03 Å) bonds of the metallocycle are consistent with the ene-1,2-dithiolate form of the dithiolene, i.e., these are [Au(III)bis(ene-1,2-dithiolate)]− complexes. Each compound is diamagnetic and 1H NMR studies indicate that, in solution in d6-acetone, both the cis and trans isomers of the [Au(SC(H)C(R)S)2]− anion are present and do not interconvert at room temperature. Each [Au(dithiolene)2]− complex undergoes an oxidation (80

Graphical abstractFour square planar [Au(dithiolene)2]− complexes have been synthesized and characterized; they comprise Au(III) bound to two asymmetrically substituted ene-1,2-dithiolates and both cis and trans isomers are present in solution. Each complex undergoes an oxidation and a reduction, the potentials of which correlate with the electron withdrawing nature of the dithiolene.Figure optionsDownload full-size imageDownload as PowerPoint slide