Synthesis and structure of cationic guanidinate-bridged bimetallic {Li7M} cubes (M = Mn, Co, Zn) with inverse crown counter anions

Abstract

The reactions of the heteroleptic lithium amide [Li₃(μ-hmds)₂(μ,μ-hpp)] (1), where [hmds]⁻ = hexamethyldisilazide and [hpp]⁻ = hexahydropyrimidopyrimidide, with MnCl₂, CoCl₂ or ZnBr₂ result in the formation of the separated ion-pairs [MLi₇(μ₈-O)(μ,μ-hpp)₆]⁺[A]⁻, which each consist of a {MLi₇} oxo-centred cube structural motif (M = Mn 2, Co 4, Zn 5), with each face of the cube being bridged by an [hpp]⁻ ligand. In the case of M = Mn and Co, the counter ion, [A]⁻, is the pentagonal anionic inverse crown [{Li(μ-hmds)}₅(μ₅-Cl)]⁻ (3), whereas the reaction with M = Zn produces the known tris-amido zincate [Zn(hmds)₃]⁻ counter anion.