Molecular shapes octahedral

Three common molecular shapes are associated with octahedral electron group geomehy. Most often, an inner atom with a steric number of 6 has octahedral molecular shape with no lone pairs. Example uses a compound of xenon, whose chemical behavior is described in the Chemical Milestones Box, to show a second common molecular shape, square planar. 

SbFe] After bonding to one F" the central Sb now has six electron pairs around it, all of which are bonding. This results in an octahedral molecular shape. 

The Lewis stmeture of SFg, shown in Figure 9-24a. indicates that sulfur has six S—F bonds and no lone pairs. The molecular geometry that keeps the six fluorine atoms as far apart as possible is octahedral in shape, as Figure 9-24Z) shows. Figure 9-24c shows that an octahedron has eight triangular faces. 

Yuan, J., Li, W., Gomez, S. and Suib, S.L. (2005) Shape-controlled synthesis of manganese oxide octahedral molecular sieve three-dimensional nanostructures. Journal of the American Chemical Society, 127, 14184-14185. 

In PF6 there are 5 + (6 x 7) +1 = 48 valence electrons or 24 electron pairs. A plausible Lewis structure follows. Since there are six atoms and no lone pairs bonded to the central atom, the electron-group geometry and molecular shape are octahedral. 

Now you can see that the central atoms has 4 BPs and 2 LPs, a total of 6 electron groups around it. The geometric arrangement of the electron group is octahedral. For 4 BPs and 2 LPs, the molecular shape is square planar. 

Numerous d cobalt(III) complexes are known and have been studied extensively. Most of these complexes are octahedral in shape. Tetrahedral, planar and square antiprismatic complexes of cobalt(lII) are also known, but there are very few. The most common ligands are ammonia, ethylenediamine and water. Halide ions, nitro (NO2) groups, hydroxide (OH ), cyanide (CN ), and isothiocyanate (NCS ) ions also form Co(lII) complexes readily. Numerous complexes have been synthesized with several other ions and neutral molecular hgands, including carbonate, oxalate, trifluoroacetate and neutral ligands, such as pyridine, acetylacetone, ethylenediaminetetraacetic acid (EDTA), dimethylformamide, tetrahydrofuran, and trialkyl or arylphosphines. Also, several polynuclear bridging complexes of amido (NHO, imido (NH ), hydroxo (OH ), and peroxo (02 ) functional groups are known. Some typical Co(lll) complexes are tabulated below ... 

The basic molecular shapes are shown in Figure 8-6. Note that the words tetrahedral and octahedral refer to the four- and eight-sided solids formed by connecting the ligand atoms, not to the coordination numbers, which are 4 and 6, respectively. 

B Methane has a molecular geometry that is tetrahedral, while BF3 is trigonal planar in shape and XeF6 is octahedral in shape. 

Molecular shape Linear Square planar Octahedral... 

For application of MO theory to geometries other than octahedral, see Chapter 9 in J.K. Burdett (1980) Molecular Shapes Theoretical Models of Inorganic Stereochemistry, Wiley, New York. 

Molecular Shapes with Six Electron Groups (Octahedral Arrangement)... 

With six bonding groups, the molecular shape is octahedral (AXg), as in sulfur hexafluoride (SFg) ... 

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