Unexpected reactions of NHC*—CuI and —AgI bromides with potassium thio- or selenocyanate

Abstract

The reactions of N-heterocyclic carbene CuI and AgI halides with potassium thio- or selenocyanate gave unexpected products. The attempted substitution reaction of bromido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)silver (NHC*—Ag—Br) with KSCN yielded bis[bis(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)silver(I)] tris(thiocyanato)argentate(I) diethyl ether disolvate, [Ag(C29H24N2)2][Ag(NCS)3]·2C4H10O or [NHC*2Ag]2[Ag(SCN)3]·2Et2O, (1), while reaction with KSeCN led to bis(μ-1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-κ2Se:Se)bis[bromido(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-κSe)silver(I)] dichloromethane hexasolvate, [Ag2Br2(C29H24N2Se)4]·6CH2Cl2 or (NHC*Se)4Ag2Br2·6CH2Cl2, (2), via oxidation of the NHC* fragment to 2-selenoimidazole. This oxidation was observed again in the reaction of NHC*—Cu—Br with KSeCN, yielding catena-poly[[[(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-κSe)copper(I)]-μ-cyanido-κ2C:N] acetonitrile monosolvate], {[Cu(CN)(C29H24N2Se)]·C2H3N}n or NHC*Se—CuCN·CH3CN, (3). Compound (1) represents an organic/inorganic salt with AgI in a linear coordination in each of the two cations and in a trigonal coordination in the anion, accompanied by diethyl ether solvent molecules. The tri-blade boomerang-shaped complex anion [Ag(SCN)3]2− present in (1) is characterized by X-ray diffraction for the first time. Compound (2) comprises an isolated centrosymmetric molecule with AgI in a distorted tetrahedral BrSe3 coordination, together with dichloromethane solvent molecules. Compound (3) exhibits a linear polymeric 1∞[Cu—C[triple-bond]N—Cu—] chain structure with a selenoimidazole moiety additionally coordinating to each CuI atom, and completed by acetonitrile solvent molecules. Electron densities associated with an additional ether solvent molecule in (1) and two additional dichloromethane solvent molecules in (2) were removed with the SQUEEZE procedure [Spek (2015). Acta Cryst. C71, 9–18] in PLATON.

Keywords

• n-heterocyclic carbene
• copper(i)
• silver(i)
• thiocyanate
• selenocyanate
• d10 electron configuration
• crystal structure