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

Abstract

We herein report the synthesis, structures, coordination ability, and mechanism of formation of silicon analogs of crown ethers. An oligomerization of 2D2 (I) (2Dn,=(Me4Si2O)n) was achieved by the reaction with GaI3 and MIx (M=Li, Na, Mg, Ca, Sr). In these reactions the metal cations serve as template and the anions (I−/[GaI4]−) are required as nucleophiles. In case of MIx=LiI, [Li(2D3)GaI4] (1) is formed. In case of MIx=NaI, MgI2, CaI2, and SrI2 the compounds [M(2D4)(GaI4)x] (M=Mg2+ (3), Ca2+ (4), Sr2+ (5) are obtained. Furthermore the proton complex [H(2D3)][Ga2I7] (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 2Dn and other ligands and to shed light on the formation of larger rings from smaller ones.