Syntheses, crystal structures, reactivity, and photochemistry of gold(iii) bromides bearing N-heterocyclic carbenes

Abstract

Gold(I) complexes bearing N-heterocyclic carbenes (NHC) of the type (NHC)AuBr (3a/3b) [NHC = 1-methyl-3-benzylimidazol-2-ylidene (= MeBnIm), and 1,3-dibenzylimidazol-2-ylidene (= Bn 2 Im)] are prepared by transmetallation reactions of (tht)AuBr (tht = tetrahydrothiophene) and (NHC)AgBr (2a/2b). The homoleptic, ionic complexes [(NHC) 2 Au]Br (6a/6b) are synthesized by the reaction with free carbene. Successive oxidation of 3a/3b and 6a/6b with bromine gave the respective (NHC)AuBr 3 (4a/4b) and [(NHC) 2 AuBr 2 ]Br (7a/7b) in good overall yields as yellow powders. All complexes were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. Reactions of the Au(III) complexes towards anionic ligands like carboxylates, phenolates and thiophenolates were investigated and result in a complete or partial reduction to a Au(I) complex. Irradiation of the Au(III) complexes with UV light yield the Au(I) congeners in a clean photo-reaction.

Synthesis, Characterization and Luminescence of Silver(I) and Gold(I) Complexes Bearing a Diethyl Acetal Functionalized N-Heterocyclic Carbene

“…This value is very similar to that of analogous NHC-Ag complexes of the type [(NHC) 2 Ag][AgBr 2 ] [7,10]. The chemical shift of the C2 carbene carbon atom of the gold complex 3 is 184.3 ppm, which is at the down field limit of comparable NHC-Au-Br complexes [7]. The ESI mass spectra of 2 and • ) with two different Ag···Ag distances of 3.436(1) for Ag1-Ag2 and 3.668(1)Å for Ag2-Ag1 ii .…”

“…Therefore, this aggregation might be governed mainly by Coulombic or multipolar interactions (e. g. quadrupole-quadrupole interactions which in certain cases can even outperform metallophilic interactions [14]). It should be noted that this aggregation pattern is frequently found for silver halide complexes bearing NHC ligands, but is rarely observed with other ligands [7]. The imidazolyl ring planes are almost exactly coplanar (N1-C1-C11-N3 178.2…”

“…NHC-Au(I) complexes are investigated due to numerous applications ranging from homogeneous catalysts for unique C-C, C-O, and C-N bond forming reactions [3,4] to pharmaceutical uses as anticancer, antiarthritis, and antibacterial agents [5,6]. The chemistry of gold is dominated by compounds of the metal in the oxidation state +1 in linearly coordinated complexes of the type NHC-Au-X or [(NHC) 2 Au]X, which are prepared by the reaction of (R 2 S)AuX (R 2 S = Me 2 S, tetrahydrothiophene; X = halide) with an NHC-Ag complex or the free carbene [7]. In the course of our studies on Ag(I), Au(I) and Au(III) complexes bearing NHCs functionalized with nitrogen donor atoms [8 -10], we became also interested in examples with oxygen containing side arms at a nitrogen atom of the NHC ligands.…”

Synthesis, Characterization and Luminescence of Gold Complexes Bearing an NHC Ligand Based on the Imidazo[1,5‐a]quinolinol Scaffold

“…As observed for other mixed (NHC)AuXY 2 (X, Y = halide) complexes, the more electronegative chloride is in a trans position relative to the carbene carbon atom. [21,23] All Au-C and Au-www.eurjic.org FULL PAPER halide distances are in the expected range. Compared with 5, the Au···O distance decreases significantly to 2.717(1) Å, presumably due to the higher charge of the coordinated metal.…”

“…[22,23] + (X = Cl, Br) is common for phosphane gold(I) complexes, but relatively seldom reported for L = NHC. [24] Note that the corresponding complexes [(LAu) 2 X]Y (L = R 3 P, Y = weakly coordinating anion) have previously been prepared and structurally characterized.…”