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Part 3, Substitution reactions in square planar complexes, Trans effect.pptx
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