Synthetic and structural studies of silver(I)- and gold(I)-containing N-heterocyclic carbene metallacrown ethers

The ligands bis(imidazolium) hexafluorophosphate [RHimy(CH2OCH2)(n)-HimyR][PF6](2) [Himy = -C3N2H3-, imidazolium; R = 1-naphthylmethyl, n = 2 (1a), 3 (2a); R = 9-anthracenylmethyl, n = 2 (1b), 3 (2b)] with a highly flexible polyether chain were easily prepared by the reaction of substituted imidazole with the corresponding polyglycol diiodide, followed by exchange of the anions with PF6-. Ligands 1a,b and 2a,b react with Ag2P to give monometallic Ag-I-containing N-heterocyclic carbene (NHC) metallacrown ethers 3a,b and 4a,b with a long and highly flexible bridging chain (CH2OCH2), (n = 2, 3) between the two imidazolium units. Complexes 3a,b and 4a,b react with [Au(SMe2)Cl] in a transmetalation reaction to give Au-I analogues 5a,b and 6a,b. Complexes 3a,b-6a,b are novel examples of a metallacrown ether with NHCs. In contrast to the use of a high-dilution technique in the preparation of polyether chain phosphane-containing metallacrown ethers, the new trans-metallacrown ethers can be prepared in concentrated solution. The structures of 3a-6a were confirmed by X-ray diffraction determination. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).