TETRAHEDRAL AND OCTAHEDRAL STRUCTURES

For linear, trigonal planar, tetrahedral, and octahedral structures, all ligand positions are equivalent. The trigonal bipyramidal structure, on the other hand, has two kinds of ligand sites—axial and equatorial. Each axial electron pair is 90° away from three equatorial pairs and 180° away from the other axial pair. Each equatorial pair is 90° away from two axial pairs and 120° from the other two equatorial pairs. Electron repulsion is slightly greater for the axial pairs, so that a more repulsive electron pair is better off at an equatorial site. Thus for an SN = 5 molecule with an unshared electron pair such as SF4, the... 

Octahedral and tetrahedral solvates (A1S )(C104)3 [n = 4,6 S = trimethyl phosphate (TMPA), hexamethylphosphorotriamide (HMPT), triethyl phosphate (TEPA), dimethyl methylphosphonate (DMMP), diethyl ethylphosphonate (DEEP), and dimethyl hydrogen phosphite (DMHP)] are shown by Al NMR to have tetrahedral and octahedral structures which are retained in nitromethane solution. 

For transition metals, the more common features of coordination complexes is summarized by the following they work by using 3d orbitals, the most common oxidation numbers are 4 and 6, so they form tetrahedral and octahedral structures most often. 

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