Rh. Huang et al., COMPLEXATION OF THE CATIONS OF 6 ALKALIDES AND AN ELECTRIDE BY MIXED CROWN-ETHERS, Journal of the American Chemical Society, 115(21), 1993, pp. 9542-9546
It is well-known that crown ethers form sandwich complexes with the ca
tions of many metals, but to date, the same crown ether formed both ha
lves of the sandwich. Six new alkalides and an electride have now been
synthesized that contain mixed sandwich complexes of alkali metal cat
ions with 18-crown-6 (18C6), 15-crown-5 (15C5), and 12-crown-4 (12C4).
The properties of Cs+(18C6)(15C5)Na- and Cs+(18C6)(15C5)e- demonstrat
e the existence of these stoichiometric compounds, but single-crystal
X-ray diffraction studies yielded only the crystal systems and cell pa
rameters. The crystal structures of K+(18C6)(12C4)Na-, K+(18C6)(12C4)K
-, K+(18C6)(12C4)K-.18C6, Rb+(18C6)(12C4)Na-, and Rb+(18C6)(12C4)Rb-we
re determined, thus verifying the thermodynamic stability of the mixed
sandwich compounds relative to the ''parent' compounds that contain o
nly one type of complexant.