Structural chemistry of vanadium oxides with open frameworks

The present work is dedicated to a crystal-chemical and topographical analy sis of vanadium oxides with open structures. The review covers, apart from a few exceptions, only pure vanadium oxide structures with vanadium in oxid ation states greater than +3. Purely tetrahedral frameworks are not discuss ed because of their traditional, well known crystal chemistry and only a fe w examples of cluster compounds are provided. Structural classification and notation of vanadium oxide frameworks are proposed based on the following scheme: polyhedra --> chain --> layer --> three-dimensional framework. Thus , approximately 60 types of vanadium oxide frameworks are divided into five classes by type of coordination polyhedra present and into 14 subclasses b y a more complex structural formation. Details are also given of the analys is of vanadium-oxygen coordination polyhedra and their metamorphosis: tetra hedron-trigonal bipyramid-square pyramid-octahedron, as well as the combina torial deduction of possible structures for the most common framework types .