This document discusses the catalytic cycle of organometallic compounds, focusing on Wilkinson's catalyst. It describes Wilkinson's catalyst as a rhodium coordination compound used to catalyze alkene hydrogenation. The catalytic cycle involves oxidative addition of H2 to the rhodium center, formation of a pi complex with the alkene, migratory hydrogen insertion, and reductive elimination to regenerate the catalyst and produce the hydrogenated alkene product. Applications of Wilkinson's catalyst include hydroacylation, hydroboration, and hydrogenation reactions.

1. CATALYTIC CYCLE OF ORGANOMETALLIC
COMPOUND
NAME- MOUPARNA MUDI
DEPT. OF APPLIED CHEMISTRY ,MAKAUT ,WB

2. contents
 Introduction
 Wilkinson’s catalyst
 Mechanism of catalysis for the
hydrogenation
 Catalytic cycle
 Properties &uses
 Applications
 References

3. Introduction-
 a catalytic cycle is a multistep reaction mechanism that involves a catalyst. The
catalytic cycle is the main method for describing the role of catalysts in bioinorganic
chemistry, organometallic chemistry, bioorganic chemistry, materials science, etc.
 It is mainly occurred 7 types of steps –
1. Association
2. Dissociation
3. 1,1-insertion
4. 1,2-insertion
5. B-elimination
6. Oxidative addition
7. Reductive elimination

4. Wilkinson catalysts-
• it is an coordination compound whose coordination centre is rhodium.
It is extensively used as a catalyst in the hydrogenation of alkenes.
The chemical formula of Wilkinson’s catalyst can be written as [RhCl(PPh3)3]
where ‘Ph’ denotes a phenyl group.
Preparation-
Wilkinson’s catalyst can be prepared by reacting hydrated rhodium(III) chloride with excess triphenylphosphine in the
excess triphenylphosphine in the presence of ethanol (which acts as a refluxing agent). Here, the triphenylphosphine
Here, the triphenylphosphine (denoted by the chemical formula P(C6H5)3) acts as a reducing agent which has the ability

5. Mechanism of hydrogenation of alkenes-
 Initially, a 14-electron or 12-electron
complex is formed from the dissociation of 1
or 2 triphenylphosphine ligands.
 Now, the oxidative addition of molecular
hydrogen (H2) to the metal core of Wilkinson’s
catalyst (rhodium) occurs.
 The third step of the mechanism involves the
formation of a pi complex with the alkene.
 The hydrogen is inserted into the complex via
migratory insertion which could proceed
through intramolecular hydride transfer or
through olefin insertion.
 Finally, reductive elimination occurs at the
pi complex to regenerate the catalyst and
afford the required alkene product.

6. Catalytic cycle

7. Properties –
Physical properties-
 The molar mass of Wilkinson’s catalyst is
925.22grams/mole.
 It’s melting point ranges from 518 to 523K
 It is insoluble in water. However, it is
soluble in many hydrocarbon-based solvents
such as benzene and tetrahydrofuran.
Chemical properties-
 Wilkinson’s catalyst has a square planar
coordination geometry
 It reacts with carbon monoxide to yield
[RhCl(CO)(PPh3)2]
 This coordination compound undergoes
dimerization when stirred into a solution of
benzene. The chemical composition of the dimer
can be expressed as [RhCl(PPh3)2]2

8. Applications-
 Wilkinson’s catalyst can be employed for the hydroacylation of
alkenes.
 The hydroboration and hydrosilylation of olefins can also be
achieved with the help of this coordination complex.
 Functionalized tri-substituted alkenes and internal alkynes can be
subjected to hydrogenation with the help of Wilkinson’s catalyst in
the presence of hydrogen and a strong base. Here, a highly reactive
Rh(I) species having relatively superior catalytic activity is
formed
 This catalyst is highly effective in the selective reduction of the
least hindered olefin when there are several olefins present.