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On the Crystal Chemistry of Oxometallates of Cadmium
Author(s) -
MüllerBuschbaum Hanskarl
Publication year - 2009
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200900120
Subject(s) - crystallography , octahedron , crystal structure , chemistry , lone pair , crystal chemistry , aurivillius , polyhedron , coordination number , tetrahedron , materials science , ion , molecule , combinatorics , mathematics , optoelectronics , organic chemistry , dielectric , ferroelectricity
In oxo/‐vanadates, ‐chromates, ‐wolframates, ‐germanates, for example, Cd 2+ appears as cationic part of the crystal structures and shows mainly octahedral coordination by oxygen. It is amazing that CdMoO 4 (Scheelite type) and α‐CdUO 4 are containing CdO 8 ‐polyhedra. The first mentioned compound shows distorted two times capped trigonal CdO 6+2 prisms, in α‐CdUO 4 the coordination number eight is realized by CdO 8 ‐cubes. The only one example of sevenfold coordinated Cd 2+ is CdV 3 O 7 . The compound CaCd 2 Bi 2 Nb 4 O 15 shows in the anionic part of the crystal structure Nb 4 O 15 blocks (allocated to the Aurivillius phases). The NbO 6 ‐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: BaCdO 2 ; RbCdO 2 ; K 2 Cd 2 O 3 ; K 6 CdO 4 ; Cs 2 K 2 Cd 3 O 5 and Cs 14 Cd 9 O 16 . 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 Cd 2+ . Special structural features found in the crystal structure of Cs 14 Cd 9 O 16 are Cd 9 O 16 ‐polyhedra blocks. Na 2 CdO 2 is no member of the oxocadmates because of the common statistically distribution of large alkali Na + and Cd 2+ ions at the same point position of oxygen in the Bixbyite (Mn 2 O 3 ) type. Despite the fact that Cs 2 K 2 Cd 3 O 5 is a member of metal rich compounds it shows Cs + inside a large extremely deformed CsO 7 ‐polyhedron. Cd 3 Bi 10 O 20 and CaCd 2 Bi 2 Nb 4 O 15 are examples of lone pair activity of Bi 3+ . A special feature of Cd 3 Bi 10 O 20 is the common use of one lone pair coming from two Bi 3+ ions.