Cyclic Dimethylsiloxanes as Pseudo Crown Ethers: Syntheses and Characterization of Li(Me2SiO)5[Al{OC(CF3)3}4], Li(Me2SiO)6[Al{OC(CF3)3}4], and Li(Me2SiO)6[Al{OC(CF3)2Ph}4]

An unexpected guest: The salts LiD5[AlF], LiD6[AlF], and LiD6[AlPhF] (Dn=(Me2SiO)n; [AlF]=Al{OC(CF3)3}4; [AlPhF]=Al{OC(CF3)2Ph}4) are the first host–guest complexes to be synthesized directly from cyclic dimethylsiloxanes, alkali-metal ions, and weakly coordinating anions. Their experimental and calculated structures imply that the cyclic dimethylsiloxanes act as pseudo crown ethers (see structure of [LiD6]+).