cyclo-P₄ Building Blocks: Achieving Non-Classical Fullerene Topology and Beyond

The cyclo-P₄ complexes [Cp^R Ta(CO)₂ (η⁴ -P₄ )] (Cp^R : Cp''=1,3-C₅ H₃ tBu₂ , Cp'''=1,2,4-C₅ H₂ tBu₃ ) turned out to be predestined for the formation of hollow spherical supramolecules with non-classical fullerene-like topology. The resulting assemblies constructed with CuX (X=Cl, Br) showed a highly symmetric 32-vertex core of solely four- and six-membered rings. In some supramolecules, the inner cavity was occupied by an additional CuX unit. On the other hand, using CuI, two different supramolecules with either peanut- or pear-like shapes and outer diameters in the range of 2-2.5 nm were isolated. Furthermore, the spherical supramolecules containing Cp''' ligands at tantalum are soluble in CH₂ Cl₂ . NMR spectroscopic investigations in solution revealed the formation of isomeric supramolecules owing to the steric hindrance caused by the third tBu group on the Cp''' ligand. In addition, a 2D coordination polymer was obtained and structurally characterized.