Coordination Polyhedra LnOn (Ln = Tb,Dy, Ho) in Crystal Structures

The Voronoi-Dirichlet polyhedra (VDP) were used to study the stereochemical features of terbium, dysprosium, and holmium surrounded by oxygen in the structures of 456 compounds. The Tb, Dy, and Ho atoms have C.N.s of 6 to 12 with respect to oxygen. The volume of the VDP of lanthanide atoms does not depend on their C.N. or the shape of the coordination polyhedron, although the Ln(III)-O bond length changes by 0.6–0.7 Å. The Tb(III) → Tb(IV) transition is accompanied by a decrease in the terbium VDP volume by ～2 ų.