NHC Gold(III) Triflimidate Complexes

Abstract

Substitution of a trans chloride ligand in the Nheterocyclic carbene (NHC) Au III complexes (NHC)AuCl 3 in the presence of AgNTf 2 yields a new family of (NHC)AuCl 2 (NTf 2 ) complexes. They display a moderate stability in solution but are stable once crystallized. These new organogold(III) complexes could be fully characterized by NMR, IR, and single crystal X-ray diffraction. They exhibit in 13 C{ 1 H} NMR an unusually upfield-shifted resonance associated with the carbene center.

New Experimental Evidences Regarding Conformational Equilibrium in Ammonium−Bis(trifluoromethanesulfonyl)imide Ionic Liquids

“…These values compare nicely with the data reported for the trifuoromethyl carbon-trifuoromethyl carbon distances in crystals containing different cations and cis-TFSI [55] or trans-TFSIanions, [56,57] that are, respectively, 4.00 and, on average, 5.06 Å . These figures seem to be in closer agreement with the results of the MD simulations with the DLPOLY model, than by means of the GAFF force field.…”

“…Another evident difference between the two force field models is the position of the two peaks, that in GAFF models are considerably shifted to higher distances in both liquids (4.13/ 5.09 Å -GAFF vs. 4.05/4.98 Å -DLPOLY for TMHA-TFSI and 4.23/ 5.09 Å -GAFF vs. 4.01/4.98 Å -DLPOLY-for TMPA-TFSI. These values compare nicely with the data reported for the trifuoromethyl carbon-trifuoromethyl carbon distances in crystals containing different cations and cis-TFSI [55] or trans-TFSIanions, [56,57] that are, respectively, 4.00 and, on average, 5.06 Å . The mean value of the difference between crystal data and the predictions of both simulations is around 1.6 %, DLPOLY being more accurate for TMPA-TFSI and GAFF for TMHA-TFSI.…”

Synthesis, Characterization, and Catalytic Activity of Cationic NHC Gold(III) Pyridine Complexes

“…Their values range from 120.0 to 131.6 ppm and are very close to those reported for the related [(NHC)AuCl 2 (NTf 2 )] complexes. 23 The 31 P NMR spectra confirm the cationic character of 5−8 with the presence of the PF 6 − anion. The arrangement of two symmetrical Cl cis ligands around the gold center is confirmed by the appearance in the infrared spectrum of an intense ν(Au−Cl) absorption band between 372 and 385 cm −1 .…”

Visible‐Light‐Promoted AuI to AuIII Oxidation in Triazol‐5‐ylidene Complexes

“…However, due to the high redox potential of the Au I /Au III couple ( E 0 =+1.41 V), the organometallic chemistry of gold(III) with NHCs appears less developed than for gold(I) species and is mainly restricted to neutral halide Au III complexes, and there is strong evidence for an in situ reduction of simple gold(III) catalysts by oxidative C−C coupling in the intermediates . A common methodology to attain the oxidation of NHC‐Au I species relies on the addition of strong oxidants such as fluorinating or hypervalent iodine reagents, or treatment with molecular Cl 2 , Br 2 , or I 2 ,. More recently, a few outstanding examples of oxidative addition to C−Br/I and C−C bonds onto Au I have been reported by Bourissou and Toste .…”