Three new tellurite halides with unusual Te4+ coordinations and iron honeycomb lattice variants

The crystal structure of three new iron and copper-iron tellurite halides are presented; (I) Cu3Fe8Te12O32Cl10 that crystallizes in the orthorhombic space group Pmmn, (II) Fe8Te12O32Cl3Br3 that crystallizes in the monoclinic space group P21/c, and (III) Fe5(TeO3)6Cl2 that crystallizes in the triclinic space group P-1. The crystal structures were solved from single crystal X-ray diffraction data. All three compounds have layered crystal structures where the Fe atoms form variants of the honeycomb lattice. Highly unusual Te4+ coordination polyhedra are exemplified: [TeO3+1E], [TeO3XE], [TeO3+1XE], and [TeO3X2E] (X=halide ion, E=the lone–pair valence electrons). The crystal structures contain large non-bonding volumes occupied by the stereochemically active lone–pair electrons on Te4+.