Q135P - Chemistry: Molecular Nature Of Matter And Change

Question

A shortcut to finding optical isomers is to see if the complex has a plane of symmetry-a plane passing through the metalatom such that every atom on one side of the plane is matched by an identical one at the same distance from the plane on the other side. Any planar complex has a plane of symmetry since all atoms lie in one plane. Use this approach to determine whether these exist as optical isomers: 

(a)$\left[\text{Zn}{\left({\text{NH}}_3\right)}_2{\text{Cl}}_2\right]$  (tetrahedral);

(b) ${\left[\text{Pt}{\left(\text{en}\right)}_2\right]}^{\mathbf{2}\mathbf{+}}\mathbf{;}$  

(c)  trans-${\mathbf{\left[}{\mathbf{\text{PtBr}}}_{\mathbf{4}}{\mathbf{\text{Cl}}}_{\mathbf{2}}\mathbf{\right]}}^{\mathbf{2}\mathbf{-}}$ ; 

(d) $\mathit{t}\mathit{r}\mathit{a}\mathit{n}\mathit{s}\mathbf{-}\mathbf{[}\mathbf{C}\mathbf{o}\mathbf{(}\mathbf{e}\mathbf{n}{\mathbf{)}}_{\mathbf{2}}{\mathbf{F}}_{\mathbf{2}}{\mathbf{]}}^{\mathbf{+}}$

(e) cis- .${\left[\text{Co}{\left(\text{en}\right)}_2{\text{F}}_2\right]}^{+}$

Step-by-Step Solution

Answer

a) Does not have optical isomer

b) Does not have optical isomer 

c) Does not have optical isomer 

d) Does not have optical isomer 

e) Does not have optical isomer 

Step 1: Given information

 

Any planar complex has a plane of symmetry since all atoms lie in one plane

Step 2: Optical isomers

Optical isomers - they occur when molecule can not be superimposed with its similitude
If the plane of symmetry exists, there are not any optical isomers. If there's no plane of symmetry, then optical isomers exist.

Step 3: Find optical isomers for part a)

a) 

 $\left[\text{Zn}{\left({\text{NH}}_3\right)}_2{\text{Cl}}_2\right]$(tetrahedral) - this complex contains plane of symmetry, so it doesn't have optical isomers.

Step 4: Find optical isomers for part b

b)

${\left[\text{Pt}{\left(\text{en}\right)}_2\right]}^{2+}$ - this complex contains plane of symmetry, so it doesn't have optical isomers

Step 5: Find optical isomers for part c)

c)  $trans - {\left[PtBr{\_}_{4}C{l}_2\right]}^{2^{-}}$this complex contains plane of symmetry, so it has no optical isomers

Step 6: Find optical isomers for part d)

d) 

 $trans-[Co(en{)}_2{F}_2{]}^{+}$this complex contains plane of symmetry, so it has no optical isomers

Step 7: Find optical isomers for part e)

$cis-[Co(en{)}_2{F}_2{]}^{+}$- this complex has no plane of symmetry, so it has optical isomers