Lindlar’s catalyst is Palladium metal partially poisoned with Lead (Pb) to make it chemoselective to certain compounds.
Palladium is a powerful reducing agent. So it is less selective and reduces an wide number of organic species. Suppose you want to reduce ethyne to ethane, then Palladium is a great hydrogenation agent to do the work. It will first convert your ethyne to ethene and then ethene to ethane almost instantly. But what if you want the ethene??? This is the idea behind the evolution of Lindlar’s catalyst.
Imagine the surface of Palladium metal with large number of active sites where the organic species binds with it in order to get reduced. What Lindlar has done is that he deactivated some of the active sites by Lead (Pb) therefore made the Palladium metal surface partially poisoned. Now the reduction of ethyne to ethane can be stopped at the ethene level because the ethene produced won’t get the active sites on the palladium surface to further bind and convert to ethane.
Preparation of Lindlars catalyst:
It is prepared by precipitating PdCl2 on CaCO3 and then mixed with Pb(OAc)2. On heating the mixture it becomes Pd-CaCo3-PbO which is Lindlar’s catalyst.
This is a review of Lindlar’s catalyst- A hydrogenation agent.
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