The present work is dedicated to a crystal-chemical and topographical analysis of vanadium oxides with open structures. The review covers, apart from a few exceptions, only pure vanadium oxide structures with vanadium in oxidation states greater than +3. Purely tetrahedral frameworks are not discussed because of their traditional, well known crystal chemistry and only a few examples of cluster compounds are provided. Structural classi®cation and notation of vanadium oxide frameworks are proposed based on the following scheme: polyhedra 3 chain 3 layer 3 three-dimensional framework. Thus, approximately 60 types of vanadium oxide frameworks are divided into ®ve classes by type of coordination polyhedra present and into 14 subclasses by a more complex structural formation. Details are also given of the analysis of vanadium± oxygen coordination polyhedra and their metamorphosis: tetrahedron±trigonal bipyramid±square pyramid±octahedron, as well as the combinatorial deduction of possible structures for the most common framework types.
A new [Ni(NH(2)CH(2)CH(2)NH(2))(2)](V(6)O(14)) compound has been synthesized hydrothermally and was found to crystallize in the monoclinic system. The single-crystal X-ray data leads to a disordered structure, which can be decomposed into two ordered models with different stacking of the V(6)O(14) layers. The structure of the layer is the same in both models and represents a new member of the V(6)O(14) series. All known structures from this series are constructed from the same chain of square pyramids (SP), which share alternatively adjacent or opposite edges of their bases. The differences lie in the orientation of the SP chains which are joined together by sharing corners with tetrahedra to form the layers. Combinatorial analysis of the V(6)O(14) structures was conducted, yielding ten possible symmetry groups for the series of V(6)O(14) layers. The known structures belong only to the three simplest cases with the highest symmetry.
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