Synthetic and Structural Studies of Silver( I )‐ and Gold( I )‐ContainingN‐Heterocyclic Carbene Metallacrown Ethers

The ligands bis(imidazolium) hexafluorophosphate [RHimy‐(CH 2 OCH 2 ) n ‐HimyR][PF 6 ] 2 [Himy = –C 3 N 2 H 3 –, 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 PF 6 – . Ligands 1a , b and 2a , b react with Ag 2 O 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 (CH 2 OCH 2 ) n ( n = 2, 3) between the two imidazolium units. Complexes 3a , b and 4a , b react with [Au(SMe 2 )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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)