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ChemInform Abstract Compound (I) crystallizes in the space group C2/m with Z=2; (II) in C2/c with Z=4. These structures show that the large complexed cations form closest packed arrays, leaving anionic sites that are isolated from each other, except for rather constricted channels that interconnect them. Each anionic site is surrounded by eight complexed cations and by six other anionic sites. The compound (II) is isostructural with the analogous electride. This provides important information about the nature of the electron-trapping site and indeed Na-can be substituted for e-in one, two, or three sites around the complexed Cs cation as shown by 133Cs MAS NMR studies.

The Rb K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra of compounds with stoichiometries RbNa(18C6), Rb(18C6), Rb2(18C6), RbNa(15C5)2, Rb(15C5)2, Rb(15C5), RbK(C222), CsRb(18C6)2, RbK(18C6), RbK(15C5)2, CsRb(15C5)2, Rb(C222), and Rb2(C222) have been measured and interpreted. The XANES spectra provide a means of identifying the oxidation state of the rubidium-containing species in these salts. The compounds Cs+(18C6)2,Rb", K+(C222),Rb", and Cs+(15C5)2,Rb" are pure rubidides. They show no detectable EXAFS, consistent with the large size of Rb". The spectra of Rb+(18C6),Na", Rb+(15C5)2,Na", Rb+(15C5)2,e", and Rb+(C222),e" are similar to (but not identical with) those of the model compounds Rb+(18C6),Br"2H2Ó and Rb+(18C6)SCN". The compounds Rb+(15C5)2,Rb", Rb+(18C6),Rb", Rb(18C6), Rb+(C222),Rb", RbK(18C6), and RbK(15C5)2,e" are mixtures that contain both the complexed rubidium cation and the rubidide anion. The EXAFS data for Rb+(15C5)2,e" and Rb+(15C5)2,Rb" indicate local structures around the rubidium cation similar to that of Rb+( 15C5)2,Na", a sodide whose crystal structure has been determined by X-ray diffraction. The radial distribution functions of the compounds Rb+(18C6),X" indicate different conformations of the 18-crown-6 ring in different salts.A number of compounds that contain novel types of anionic species have been synthesized in our laboratory.1"4 Alkalides

ChemInform Abstract (complexed by the crown ethers 18C6 and 15C5 and the cryptand C222).