This ppt will helpful in understanding substitution reactions in square planar complexes especially trans effect

1. Dr. Geeta Tewari
Department of Chemistry
D. S. B. Campus
Kumaun University, Nainital
Email: geeta_k@rediffmail.com
Substitution Reactions in Square
Planar Complexes: Part 3, Trans Effect

2. Trans-effect
Trans effect is the labilization (making more
reactive) of ligands that are trans to certain ligands
(spectator ligands), which can be regarded as trans-
directing ligands.
Mostly shown in square planar complexes.
Sometimes by octahedral complexes.
The cis effect is observed in octahedral complexes.

3.  Theoretically two
products are possible in
the substitution reaction
of [Pt(NO2)Cl3]2- = cis-
[Pt(NO2)(NH3)Cl2]- and
trans-
[Pt(NO2)(NH3)Cl2]-
 Actually, only trans
product is formed.
Trans-effect
Pt
Cl
Cl
Cl
NO2
Pt
Cl
Cl
NH3
NO2
Pt
H3N
Cl
Cl
NO2
+NH3
+NH3
-Cl-
-Cl-
cis
trans
2-
-
-

4. According to Chatt et al., it is due to the trans effect of the
spectator ligand.
The spectator ligand (trans-directing) directs the incoming
ligand at the trans position of it.
Trans-effect/labilizing effect/trans labile effect
Trans-effect series
H2O < OH− <F− <NH3 <RNH2<py <Cl− < Br− < SCN− < I−< NO2
− < C6H5
- <
SC(NH2)2 <H-< PR3 < C2H4 < NO < CO< CN−
Increasing order of trans-effect
Trans-effect

5. Synthesis of cis- and trans-[Pt(NH3)2(Cl2)]
Applications of Trans-effect
P
t
H
3
N
H
3
N
N
H
3
N
H
3
+
C
l
-
-
N
H
3
2
+ +
P
t
C
l
H
3
N
N
H
3
P
t
H
3
N
H
3
N
C
l
N
H
3 C
l
+
C
l
-
-
N
H
3
Pt
Cl
Cl
Cl
Cl
+NH3
2-
Pt
Cl
Cl
NH3
Cl
-
Pt
Cl
Cl
NH3
NH3
+NH3
-Cl-
-Cl-
Cis-[Pt(NH3)2(Cl2)]
Trans[Pt(NH3)2(Cl2)]

6. NO2
- > Cl- > NH3
Applications of Trans-effect
Synthesis of cis- and trans-[Pt(NH3)(NO2)(Cl2)]-
Pt
Cl
Cl
Cl
Cl
+NH3
2-
Pt
Cl
Cl
NH3
Cl
-
Pt
Cl
Cl
NO2
NH3
+NO2
-Cl-
-Cl-
-
Cis-complex
Trans-complex
P
t
C
l
C
l
C
l
C
l
+
N
H
3
2
-
P
t
C
l
C
l
N
O
2
C
l
2
-
P
t
C
l
H
3
N
N
O
2
C
l
+
N
O
2
-
-
C
l
-
-
C
l
-
-

7. Applications of Trans-effect
Synthesis of cis- and trans-[Pt(PR3)2(Cl2)]
Pt
Cl
Cl
Cl
Cl
2-
Pt
Cl
Cl
PR3
Cl
-
Pt
Cl
R3P
PR3
Cl
+PR3
-Cl-
-Cl-
-
+PR3
P
t
R
3
P
R
3
P
P
R
3
P
R
3
2
-
P
t
R
3
P
R
3
P
C
l
C
l
-
P
R
3
+
C
l
-
P
t
R
3
P
R
3
P
C
l
-
P
R
3
+
-
P
R
3
+
C
l
-

8. Applications of Trans-effect
Synthesis of isomers of [Pt(NH3)(Py)Cl Br]
P t
C l
C l
C l
C l
2 -
P t
C l
C l
N H 3
C l
-
P t
C l
C l
N H 3
B r
+ N H 3
-C l-
+ B r-
-
-C l-
+ P y
-C l- P t
P y
C l
N H 3
B r
P t
C l
C l
C l
C l
2-
P t
C l
C l
P y
C l
-
P t
C l
C l
P y
B r
+ N H 3
-C l-
+ B r-
-
-C l-
+ P y
-C l-
P t
H 3 N
C l
P y
B r
P
t
C
l
C
l
C
l
C
l
2
-
P
t
C
l
C
l
P
y
P
y
P
t
H
3
N
C
l
P
y
P
y
+
B
r
-
-
C
l
-
+
N
H
3
-
C
l
-
+
2
P
y
-
C
l
-
P
t
H
3
N
C
l
B
r
P
y
Br->Cl->Py>NH3

9. Applications of Trans-effect
Kurnakov test to distinguish cis- and trans- isomers of [PtA2X2]
P
t
C
l
C
l
N
H
3
N
H
3
+
2
t
u
-
2
C
l
-
P
t
C
l
C
l
t
u
t
u
+
2
t
u
-
2
N
H
3 P
t
u
t
u
t
t
u
t
u
2
+
P
t
C
l
H
3
N
N
H
3
C
l
+
t
u
-
C
l
-
P
t
H
3
N
N
H
3
C
l
+
t
u
-
C
l
-
P
t
H
3
N
N
H
3
t
u
2
+
+
t
u t
u