An alkoxide cluster with 18 Li+ ions encapsulating two borate anions, [(tBuO)12Li18(BO3)2]

Abstract

The title compound, bis(borato) dodeca(tert-butoxo)octadeca-lithium, [Li-18(BO3)(2)(C4H9O)(12)], is formulated conveniently as [{((BuOLi)-Bu-t)(3)(Li3BO3)}(2)((BuOLi)-Bu-t)(6)]. A central 12-membered ring and two outer six-membered rings are formed by alternating Li+ cations and alkoxide O atoms. Sandwiched between the central ring and each of the outer rings is a planar array of three further Li+ cations surrounding a [BO3](3-) anion. Thus, the molecule consists of a cationic [Li-18((OBu)-Bu-t)(12)](6+) cage encapsulating two borate anions. This compound is the first example of a structurally characterized polynuclear lithium borate, and a rare case of a lithium alkoxide cage with nuclearity greater than eight. All the alkoxide ligands are triply bridging, and the lithium ions have trigonal-planar, trigonal-pyramidal and fourfold coordination, all with major distortions from regular coordination geometry.