N,N′-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene Gold(I) Chloride

Abstract

[852445-83-1] C27H36ClAuN2 (MW 621.01) InChI = 1S/C27H36N2.Au.ClH/c1-18(2)22-11-9-12-23(19(3)4)26(22)28-15-16-29(17-28)27-24(20(5)6)13-10-14-25(27)21(7)8;;/h9-16,18-21H,1-8H3;;1H/q;+1;/p-1 InChIKey = CNJQLSINQGKZAW-UHFFFAOYSA-M Physical Data: mp >300 °C. Solubility: soluble in acetone, CH2Cl2, and THF; partially soluble in EtOAc and EtOH; insoluble in water, pentane, hexane, and diethyl ether. Form Supplied in: colorless solid; crystal structure available.1 Preparative Methods: [Au(IPr)Cl] (IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) can be synthesized with [Ag(IPr)Cl]2 and [Au(DMS)Cl]3 (DMS = dimethyl sulfide) via transmetalation in CH2Cl2 at room temperature.4 The reaction can be performed in air without further precautions. A solution of [Ag(IPr)Cl] (250 mg, 0.47 mmol) in CH2Cl2 (1 mL) was added to a solution of [Au(DMS)Cl] (138 mg, 0.47 mmol) in CH2Cl2 (5 mL), and the resulting mixture was stirred at room temperature for 2 h. After filtration of silver salts and concentration of the filtrate, the residue was chromatographed on silica gel with elution of ethyl acetate. The desired complex was obtained as a colorless solid Yield: 251 mg, (86%).4 Moreover, it is possible to perform the one-pot synthesis starting with IPr·HCl and Ag2O in CH2Cl2 and subsequent addition of [Au(DMS)Cl].1 A mixture of silver(I) oxide (2.21 g, 9.5 mmol) and N,N′-bis(2,6-diisopropylphenyl)imidazolium chloride (6.24 g, 14.6 mmol) in CH2Cl2 (60 mL) was stirred for 4 h. The mixture was filtered through Celite, and [Au(DMS)Cl] (4.4 g, 14.9 mmol) was added. The resulting mixture was stirred for 12 h, followed by addition of activated carbon. After 30 min of stirring, the mixture was filtered through Celite and the solvent was removed in vacuo. Pentane was added in large excess to the solution, resulting in immediate precipitation of a colorless solid. The solid was filtered, further washed with pentane, and dried under vacuum. Yield: 6.38 g (70%). Recently, it was shown that Ag2O can be replaced by the less costly Cu2O.5 A mixture of [Au(DMS)Cl] (118.6 mg, 0.40 mmol) and [Cu(IPr)Cl] (196.3 mg, 0.40 mmol) in CH2Cl2 (5 mL) was stirred at 40 °C for 2 h. The mixture was filtered through celite and the solvent was removed in vacuo. CH2Cl2 (3 mL) and petroleum ether (10 mL) were added, resulting in the precipitation of an off-white solid. The product was collected by filtration, washed with petroleum ether (3 × 5 mL), and obtained as a colorless solid. Yield: 209 mg (84%).5 Alternatively, the synthesis can be carried out via ligand exchange with [Au(DMS)Cl] and the free carbene in THF at room temperature.1 Due to the moisture sensitivity of the free carbene it is necessary to work under an inert atmosphere. In a glove box, a 100 mL Schlenk flask was charged with IPr (686 mg, 1.76 mmol) and 50 mL of THF, and then [Au(DMS)Cl] (500 mg, 1.70 mmol) was added. The resulting solution was kept in the dark and stirred at room temperature for 12 h. The remaining steps were then carried out in air. The resulting solution was filtered through Celite, and activated carbon was added to the filtrate, which was stirred for 4 h. The colorless solution was filtered through Celite, the solvent was reduced to dryness under vacuum, and 10 mL of CH2Cl2 was added. Pentane (20 mL) was added to the solution, resulting in the immediate precipitation of a colorless solid. The solid was further washed with pentane and dried under vacuum, to afford a colorless powder. Yield: 820 mg (75%).1 Purification: recrystallization from CH2Cl2/pentane. Handling, Storage, and Precautions: described as air and moisture stable.