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

The reactions of the heteroleptic lithium amide [Li(3)(μ-hmds)(2)(μ,μ-hpp)] (1), where [hmds](-) = hexamethyldisilazide and [hpp](-) = hexahydropyrimidopyrimidide, with MnCl(2), CoCl(2) or ZnBr(2) result in the formation of the separated ion-pairs [MLi(7)(μ(8)-O)(μ,μ-hpp)(6)](+)[A](-), which each consist of a {MLi(7)} 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)(μ(5)-Cl)](-) (3), whereas the reaction with M = Zn produces the known tris-amido zincate [Zn(hmds)(3)](-) counter anion.