Structural evolution in iron tellurates

Three new members within the iron tellurate family have been synthesized and characterized by single-crystal diffraction. image is orthorhombic, image, image, image, image, space group Pnma, final agreement factors image image for 1271 independent reflections. image is monoclinic, image, image, image, image, image, space group image, final agreement factors image image for 3302 independent reflections. image is trigonal, image, image, image, space group image, final agreement factors image image for 1264 independent reflections. Together with the four already known members of the family, image, image, and image (a dimorphic variant of the afore-mentioned structure with the same chemical formula), and image, the iron tellurates now span from relatively Fe-rich and Te-poor to relatively Fe-poor to Te-rich compounds. The structural diversity within Fe–Te–O system is discussed in terms of the lone-pair stereochemistry of the image anion and the cross-over from image to mixed-valence image and image coordination polyhedra compounds.