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In chemistry, octahedral molecular geometry describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The octahedron has eight faces, hence the prefix ''octa.'' The octahedron is one of the Platonic solids, although octahedral molecules typically have an atom in their centre and no bonds between the ligand atoms. A perfect octahedron belongs to the point group ''Oh''. Examples of octahedral compounds are sulfur hexafluoride SF6 and molybdenum hexacarbonyl Mo(CO)6. The term "octahedral" is used somewhat loosely by chemists, focusing on the geometry of the bonds to the central atom and not considering differences among the ligands themselves. For example, ()3+, which is not octahedral in the mathematical sense due to the orientation of the N-H bonds, is referred to as octahedral.〔von Zelewsky, A. "Stereochemistry of Coordination Compounds" John Wiley: Chichester, 1995. ISBN 047195599X.〕 The concept of octahedral coordination geometry was developed by Alfred Werner to explain the stoichiometries and isomerism in coordination compounds. His insight allowed chemists to rationalize the number of isomers of coordination compounds. Octahedral transition-metal complexes containing amines and simple anions are often referred to Werner-type complexes. ==Bioctahedral molecular geometry== The sharing of an edge of an octahedron gives a structure called ''bi''octahedral. Many metal pentahalide and pentaalkoxide compounds exist in solution and the solid with bioctahedral structures. One example is niobium pentachloride. Metal ''tetra''halides often exist as polymers with edge-sharing octahedra. Zirconium tetrachloride is an example.〔Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.〕 Image:Niobium-pentachloride-from-xtal-3D-balls.png|Ball-and-stick model of niobium pentachloride, a bioctahedral coordination compound. Image:Zirconium-tetrachloride-3D-balls-A.png|Ball-and-stick model of zirconium tetrachloride, an inorganic polymer based on edge-sharing octahedra. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「octahedral molecular geometry」の詳細全文を読む スポンサード リンク
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