Construction of Inorganic Crown Ethers by s-Block-Metal-Templated Si-O Bond Activation.

We herein report the synthesis, structures, coordination ability, and mechanism of formation of silicon analogs of crown ethers. An oligomerization of D (I) ( D ,=(Me Si O) ) was achieved by the reaction with GaI and MI (M=Li, Na, Mg, Ca, Sr). In these reactions the metal cations serve as template and the anions (I /[GaI ] ) are required as nucleophiles. In case of MI =LiI, [Li( D )GaI ] (1) is formed. In case of MI =NaI, MgI , CaI , and SrI the compounds [M( D )(GaI ) ] (M=Mg (3), Ca (4), Sr (5) are obtained. Furthermore the proton complex [H( D )][Ga I ] (6) was isolated and structurally characterized. All complexes were characterized by means of multinuclear NMR spectroscopy, DOSY experiments and, except for compound 3, also by single crystal X-ray diffraction. Quantum chemical calculations were carried out to compare the affinity of M to D and other ligands and to shed light on the formation of larger rings from smaller ones.