Abstract
AbstractIn oxo/‐vanadates, ‐chromates, ‐wolframates, ‐germanates, for example, Cd2+ appears as cationic part of the crystal structures and shows mainly octahedral coordination by oxygen. It is amazing that CdMoO4 (Scheelite type) and α‐CdUO4 are containing CdO8‐polyhedra. The first mentioned compound shows distorted two times capped trigonal CdO6+2 prisms, in α‐CdUO4 the coordination number eight is realized by CdO8‐cubes. The only one example of sevenfold coordinated Cd2+ is CdV3O7. The compound CaCd2Bi2Nb4O15 shows in the anionic part of the crystal structure Nb4O15 blocks (allocated to the Aurivillius phases). The NbO6‐octahedra network corresponds a yet unknown higher Ruddlesden‐Popper phase too. The so called oxocadmates are formed by the large alkaline metals and barium. For example: BaCdO2; RbCdO2; K2Cd2O3; K6CdO4; Cs2K2Cd3O5 and Cs14Cd9O16. The compositions generally show metal rich compounds stand out due low coordination numbers of the big alkaline metals. On the other hand the oxygen deficit will lead to the smallest possible tetrahedral coordination of Cd2+. Special structural features found in the crystal structure of Cs14Cd9O16 are Cd9O16‐polyhedra blocks. Na2CdO2 is no member of the oxocadmates because of the common statistically distribution of large alkali Na+ and Cd2+ ions at the same point position of oxygen in the Bixbyite (Mn2O3) type. Despite the fact that Cs2K2Cd3O5 is a member of metal rich compounds it shows Cs+ inside a large extremely deformed CsO7‐polyhedron. Cd3Bi10O20 and CaCd2Bi2Nb4O15 are examples of lone pair activity of Bi3+. A special feature of Cd3Bi10O20 is the common use of one lone pair coming from two Bi3+ ions.
Published Version
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