Abstract
The reactions of N-heterocyclic carbene CuI and AgI halides with potassium thio- or seleno-cyanate gave unexpected products. The attempted substitution reaction of bromido-(1,3-dibenzyl-4,5-di-phenyl-imidazol-2-yl-idene)silver (NHC*-Ag-Br) with KSCN yielded bis-[bis-(1,3-dibenzyl-4,5-di-phenyl-imidazol-2-yl-idene)silver(I)] tris-(thio-cyanato)-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-seleno-imidazole-κ2 Se:Se)bis-[bromido-(1,3-dibenzyl-4,5-diphenyl-2-seleno-imid-azole-κSe)silver(I)] di-chloro-methane hexa-solvate, [Ag2Br2(C29H24N2Se)4]·6CH2Cl2 or (NHC*Se)4Ag2Br2·6CH2Cl2, (2), via oxidation of the NHC* fragment to 2-seleno-imidazole. This oxidation was observed again in the reaction of NHC*-Cu-Br with KSeCN, yielding catena-poly[[[(1,3-dibenzyl-4,5-diphenyl-2-seleno-imidazole-κSe)copper(I)]-μ-cyanido-κ2 C:N] aceto-nitrile 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 mol-ecules. 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 mol-ecule with AgI in a distorted tetra-hedral BrSe3 coordination, together with di-chloro-methane solvent mol-ecules. Compound (3) exhibits a linear polymeric 1 ∞[Cu-C≡N-Cu-] chain structure with a seleno-imidazole moiety additionally coordinating to each CuI atom, and completed by aceto-nitrile solvent mol-ecules. Electron densities associated with an additional ether solvent mol-ecule in (1) and two additional di-chloro-methane solvent mol-ecules in (2) were removed with the SQUEEZE procedure [Spek (2015 ▸). Acta Cryst. C71, 9-18] in PLATON.
Highlights
Sensitive strain organisms, destroys the cell wall, impairs essential enzymes, obstructs metabolic activity and/or causes RNA and DNA alteration (Silver, 2003; Starodub & Trevors, 1989)
The attempted syntheses of the analogous NHC*—AgI and —CuI thio- and selenocyanates as potential antimicrobial species led to unexpected results with the formation of bis[bis(1,3-dibenzyl-4,5-diphenylimidazol-2ylidene)silver(I)] tris(thiocyanato)argentate(I) diethyl ether disolvate, (1), bis(-1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-2Se:Se)bis[bromido(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-Se)silver(I)] dichloromethane hexasolvate, (2), and catena-poly[[[(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-Se)copper(I)]--cyanido-2C:N] acetonitrile monosolvate], {[Cu(CN)(C29H24N2Se)]ÁC2H3N}n or NHC*Se—CuCNÁCH3CN, (3), the crystal structures of which are reported in this communication
Due to its greater distance from the anion, the benzyl groups of cation 1 have greater flexibility, allowing it to take a shape suitable to fill gaps in the packing caused by the constraint on cation 2 (Fig. 3)
Summary
Copper and silver and their compounds exhibit fungicidal properties. For example, a copper dihydroxide suspension in water – The Bordeaux Mixture – is a well-known early fungicide used in vineyards, while metallic silver has been used as an antimicrobial agent to purify drinking water for a long time. In the homologue gold series, the introduction of pseudohalide anions led to stable and bioactive compounds (Dada et al, 2017) In this context, the attempted syntheses of the analogous NHC*—AgI and —CuI thio- and selenocyanates as potential antimicrobial species led to unexpected results with the formation of bis[bis(1,3-dibenzyl-4,5-diphenylimidazol-2ylidene)silver(I)] tris(thiocyanato)argentate(I) diethyl ether disolvate, (1), bis(-1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-2Se:Se)bis[bromido(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-Se)silver(I)] dichloromethane hexasolvate, (2), and catena-poly[[[(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-Se)copper(I)]--cyanido-2C:N] acetonitrile monosolvate], {[Cu(CN)(C29H24N2Se)]ÁC2H3N}n or NHC*Se—CuCNÁCH3CN, (3), the crystal structures of which are reported in this communication. Sensitive strain organisms, destroys the cell wall, impairs essential enzymes, obstructs metabolic activity and/or causes RNA and DNA alteration (Silver, 2003; Starodub & Trevors, 1989) This topic saw renewed interest when Youngs and coworkers published the clean synthesis of N-heterocyclic (NHC) silver acetate derivatives from accessible imidazolium halides (Liang et al, 2018); NHC–silver acetates exhibit good chemical stability through covalently bonded silver, which results in significant antibiotic activity. Well suited are complexes with benzyl-substituted ligands like 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene
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