The Use of Imidazolium-2-dithiocarboxylates in the Formation of Gold(I) Complexes and Gold Nanoparticles†Dedicated to Prof. Dr. Hubert Schmidbaur on the occasion of his 75th birthday.

The imidazolium-2-dithiocarboxylate ligands IPr·CS2, IMes·CS2, and IDip·CS2 react with [AuCl(PPh3)] to yield [(Ph3P)Au(S2C·IPr)]+, [(Ph3P)Au(S2C·IMes)]+, and [(Ph3P)Au(S2C·IDip)]+, respectively. The compounds [(L)Au(S2C·IMes)]+ are prepared from the reaction of IMes·CS2 with [AuCl(L)] (L = PMe3, PCy3, CNtBu). The carbene-containing precursor [(IDip)AuCl] reacts with IPr·CS2 and IMes·CS2 to afford the complexes [(IDip)Au(S2C·IPr)]+ and [(IDip)Au(S2C·IMes)]+ with two carbene units, one bound to the metal center and the other to the dithiocarboxylate unit. Treatment of the diphosphine-gold complex [(dppm)(AuCl)2] with 1 equiv of IMes·CS2 yields [(dppm)Au2(S2C·IMes)]2+, while the reaction of [L2(AuCl)2] (L2 = dppb, dppf) with 2 equiv of IMes·CS2 results in [(L2){Au(S2C·IMes)}2]2+. The homoleptic complexes [Au(S2C·IPr)2]2+, [Au(S2C·IMes)2]2+, and [Au(S2C·IDip)2]2+ are obtained from the reaction of [AuCl(tht)] with 2 equiv of the appropriate imidazolium-2-dithiocarboxylate ligand. The compounds [(Ph3P)Au(S2C·NHC)]+ (NHC = IMes, IDip) and [(IDip)Au(S2C·NHC)]+ (NHC = IPr, IMes) are characterized crystallographically. The IMes·CS2 ligand is also used to prepare functionalized gold nanoparticles with diameters of 11.5 (±1.2) and 2.6 (±0.3) nm.