HardChemistryHigh School (11–12)Coordination Compounds › Isomerism in Coordination CompoundsNumerical
Consider the neutral octahedral platinum(IV) complex [Pt(NH₃)₂Cl₂(OH)₂]…
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Consider the neutral octahedral platinum(IV) complex . It has the form with A = NH3, B = Cl and C = OH. Find the number of geometrical isomers. Then find the number of stereoisomers when the mirror images are counted as separate forms.
Need a reminder? The key ideaShow
Cis ligands are apart and trans ligands apart. Tetrahedral complexes have no geometrical isomers. Octahedral has fac and mer forms. To count the isomers of a monodentate octahedral complex, write the ligands as three trans pairs and count the different sets. The net dipole of two bonds with dipole at an angle is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Two ammonia, two chloride and two hydroxide ligands on an octahedron.
Plan. List the sets of trans pairs. Then find which isomers have a mirror-image form.
Step 1. The sets. Calling NH3 = A, Cl = B and OH = C, the sets are AA, BB, CC; AA, BC, BC; BB, AC, AC; CC, AB, AB; and AB, AC, BC. That is 5 geometrical isomers.
Step 2. Mirror images. The first four sets each have a plane of symmetry. The last one, with all three pairs mixed, has none. It exists as two enantiomers.
Step 3. Total. stereoisomers.
Check. Geometrical isomers plus mirror-image pairs: .
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