Cage Compounds of Heterotrimetallic Mixed Phosphanediide/Silanolate Aggregates with an Alkaline Earth Metal-Centered Phosphorus Octahedron

The lithiation of potassium triisopropylsilylphosphanide yields the corresponding phosphanediide. The subsequent metathesis reaction with SrI₂ and BaI₂ in the presence of hexamethyldisiloxane gives hexalithium hexapotassium strontium hexakis(triisopropylsilylphosphanediide)bis(trimethylsilanolate) (1) and the corresponding barium derivative (2), respectively. The alkaline earth metal atoms are surrounded octahedrally by the phosphanediide ligands. Six P₃ faces of the octahedron are capped by the K atoms, and the P−P edges of two opposite P₃ faces are bridged by the lithium atoms. The Li cations are also bonded to the Me₃SiO substituents giving a coordination number of three for the alkali metals.