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[NbF7]2-

In this compound, the coordination number of 7 results in a capped trigonal prism structure.

Stereoisomers

Isomers:

are two or more molecules or ions that contain the same number and kinds of atoms (identical molecular formulas), but the atoms are arranged differently (i.e., the structures are non-superimposable),

have different physical and/or chemical properties,

do not exist for all coordination compounds,

and are generally categorized as  

1.

Structural isomers: isomers that have the same molecular formula, but one or more bonds is/are different (i.e., the connectivity between atoms is different). There are two types of structural isomers:

a.

coordination sphere isomers (occuring only for coordination complexes with associated counter ions or waters of hydration)

i.

hydration

ii.

ionization

iii.

coordination

b.

linkage isomers (occurring only for monodentate ligands possessing more than one donor atom)

2.

Stereoisomers: contain the same number and kinds of atoms, and the same number and kinds of bonds (i.e., the connectivity between atoms is the same), but the atoms are arranged differently in space. There are two types of stereoisomers:

a.

geometric isomers, and

b.

optical isomers.

Geometric isomers and optical isomers occur not only for organic compounds as previously discusse but also with many coordination compounds.

In order to be isomers, the two compounds must have the same molecular formula and have nonsuperimposable structures.

The two square planar structures above have the same molecular formula (one each of green, yellow, purple, brown and pink), and appear to be arranged differently in space. Through some combination of rotating, twisting and/or turning one of the structures we find an orientation in which all of the atoms match up with the other structure. This means that the two structures are superimposable (placing the translated structure on top of the other). These two structures are not superimposable and are not isomers.

The two tetrahedral structures above also possess identical molecular formulas (one each of yellow, red, blue, white and gray), and appear to be arranged differently in space. No combination of translations (rotations, flips, or twists) results in an orientation in which all of the atoms match up with the other

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