The Prototype centro-Cl-tetrahedro-Zn₄-icosahedro-(µ-SPh)₁₂-tetrahedro-(ZnSPh)₄ Molecular Structure, and Topological Analysis of Surface Ligand Packing for an Ensemble of High Symmetry M₈(µ-SR)₁₂ Aggregates and Derivatives

Abstract

The aggregate [ClZn₈( SPh )16]^- (1) has been characterized by diffraction analysis of crystals obtained as the minor product from a mixture of Zn(NO₃)₂, PhSH , Et₃N and Me₄NCl in methanol. The new and prototypical structure of (1) contains a bitetrahedron (tetracapped tetrahedron) of zinc atoms, centred by the monatomic ligand and bridged on the twelve edges by thiolate ligands , and with four terminal thiolate ligands. All metal atoms are tetrahedrally coordinated. In terms of expanding concentric regular polyhedra (1) is centro-Cl-tetrahedro-Zn₄-icosahedro -(μ- SPh )₁₂-tetrahedro-Zn₄-tetrahedro-( SPh )₄, introducing the structural principle of aggregation in which metal atoms are inside and outside a regular polyhedron of bridging ligands. The cage framework and the substituents of the bridging ligands virtually adhere to the symmetry of the rare point group T: the packing of obliquely inclined ligand substituents over the surface of the aggregate is responsible for this unusually high symmetry configuration. Alternative aggregate stereochemistries bitetrahedro-M₈-cuboctahedro-(μ-SR)₁₂, hexahedro-M₈- icosahedro (μ-SR)₁₂, and hexahedro-M₈-cuboctahedro-(μ-SR)12, structurally plausible and accessible to (1) without bond breaking or angular strain, are analysed topologically. Again high symmetry is required in the array of substituents from bridging ligands . It is shown that in these aggregates based on a (μ-SR)₁₂M₈ framework, the polyhedron formed by the twelve a-carbon atoms of substituents and the S₁₂ polyhedron manifest an icosahedron/cuboctahedron complementarity. Crystal data: orthorhombic P bcn, a 23.493(3), b 29.726(4), c 17.835(2), Z = 8×[Cl_0.5Zn₄(SC₆H₅)_8- + uncertain cation], 2715 observed data, Cu Kα, R = 0.12. Identification of the central ion of (1) as Cl ^- rather than the possible alternative s^2- is not definite.