Synthesis and Structure of a Novel Lithium Gallosiloxane Containing a Ga4Si4O8 Macrocycle Analogous to the S8R Building Unit of Zeolites

The reaction of LiGaMe4 with diphenysilanediol in THF at 50 °C leads to the formation of the title gallosiloxane Li2(Li(THF)2)2[Ph2SiO2GaMe2]2[Ph2SiO2GaMe(OH)]2·2THF (1), which is made up of a central tetraanionic Ga4Si4O8 16-membered macrocyclic core. The cavity that is created by this tetraanionic gallosiloxane ring and also the presence of two Ga−OH groups pointing toward the center of the macrocyclic ring facilitate the entrapment of two lithium cations in the core through two Li−O(siloxide) and two Li−OH(Ga) linkages. The other two lithium ions are located at the periphery and are bound to the gallosiloxane ring through the Li−O(Si) linkages. Compound 1 represents the first organic-soluble molecular model compound for the S8R secondary building unit of several gallo- and aluminosilicates.