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

摘要

We herein report the synthesis, structures, coordination ability, and mechanism of formation of silicon analogs of crown ethers. An oligomerization of D-2(2) (I) (D-2(n),=(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(D-2(3))GaI4] (1) is formed. In case of MIx=NaI, MgI2, CaI2, and SrI2 the compounds [M(D-2(4))(GaI4)(x)] (M=Mg2+ (3), Ca2+ (4), Sr2+ (5) are obtained. Furthermore the proton complex [H(D-2(3))][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 D-2(n) and other ligands and to shed light on the formation of larger rings from smaller ones.