Chiral, Neutral, and Paramagnetic Gold Dithiolene Complexes Derived from Camphorquinone

Abstract

AbstractReaction of racemic (dl)‐ or enantiopure (D)‐camphorquinone with P4S10in dimethylimidazolidinone followed by addition of NiCl2·6H2O or KAuCl4affords the corresponding bornylenedithiolato metal complexes [(dl‐bordt)2Ni], [(D‐bordt)2Ni], [(dl‐bordt)2Au], and [(D‐bordt)2Au] in their neutral form. Cyclic voltammetry and UV/Vis/NIR spectrometry show that the bornylenedithiolato ligand acts as a highly electron‐rich dithiolene ligand. Complete assignment of the1H and13C NMR signals of the diamagnetic enantiopure [(D‐bordt)2Ni] is reported thanks to a combination of 2D NMR spectroscopy experiments. X‐ray crystal structure determinations were performed for the four complexes, showing that the two diastereomeric mixtures, [(dl‐bordt)2Ni] and [(dl‐bordt)2Au], are isomorphous (space groupP21/c), as are also the two enantiopure complexes, [(D‐bordt)2Ni] and [(D‐bordt)2Au] (space groupP21). Positional disorder of the two (D)‐ and (L)‐bornylenedithiolate enantiomers on the same position is observed in the structure of the diastereomeric mixtures, with the complex located on the inversion center. The temperature dependence of the magnetic susceptibility of the paramagnetic gold complexes [(dl‐bordt)2Au] and [(D‐bordt)2Au] demonstrates the presence of antiferromagnetic interactions, to a larger extent in the diastereoisomeric mixture [(dl‐bordt)2Au] than in the enantiopure complex [(D‐bordt)2Au], as a consequence of stronger lateral S···S intermolecular interactions in the former. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)