文摘
A series of amidinium鈥揷arboxylate salts, [FcC{N(Cy)H][Ob>2b>CR鈥测€瞉 (Fc = ferrocenyl, R鈥测€?= Me, tBu, Ph, mesityl, CFb>3b>) have been synthesized and structurally characterized. In each case, the amidinium cation forms two NH路路路O hydrogen bonds to carboxylate anions. The extent of aggregation is, however, dependent on the carboxylate substituent. For R鈥测€?= Me, a 1:1 salt is observed with an {E,E}-configuration of cyclohexyl groups within the amidinium component, whereas R鈥测€?= tBu forms a 2:2 dimeric salt with an {E,Z}-cation. This latter configuration generates a planar chiral cation. When R鈥测€?= Ph or mesityl, the hydrogen-bonding forms a helical polymer, with each chain containing a single enantiomeric form of the cation. In contrast, when R鈥测€?= CFb>3b> the hydrogen-bonded polymer contains alternating enatiomeric forms of the cation.