Palladium on carbon explained

Palladium on carbon, often referred to as Pd/C, is a form of palladium used as a catalyst.^[1] The metal is supported on activated carbon to maximize its surface area and activity.

Uses

Hydrogenation

Palladium on carbon is used for catalytic hydrogenations in organic synthesis. Examples include reductive amination,^[2] carbonyl reduction, nitro compound reduction,^{[3] [4]} the reduction of imines and Schiff bases and debenzylation reactions.

Hydrogenolysis

Palladium on carbon is a common catalyst for hydrogenolysis. Such reactions are helpful in deprotection strategies. Particularly common substrates for hydrogenolysis are benzyl ethers:^[5]

Other labile substituents are also susceptible to cleavage by this reagent. ^[6]

Coupling reactions

Palladium on carbon is also used for coupling reactions. Examples include the Suzuki reaction and Stille reaction.^[7]

Preparation

A solution of palladium chloride and hydrochloric acid is combined with aqueous suspension of activated carbon. The palladium(II) is then reduced by the addition of formaldehyde.^[8] Palladium loading is typically between 5% and 10%. Often the catalyst mixture is stored moist.

See also

• Palladium black
• Platinum on carbon
• Platinum dioxide
• Rhodium-platinum oxide
• Lindlar catalyst
• Raney nickel
• Urushibara nickel

Notes and References

1. Book: Nishimura. Shigeo. Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis. 2001. Wiley-Interscience. New York. 9780471396987. 34–38. 1st.
2. Romanelli. Michael G.. Becker. Ernest I.. Ethylp-dimethylaminophenylacetate. Organic Syntheses. 1967. 47. 69. 10.15227/orgsyn.047.0069.
3. Book: Michael B. . Smith . Jerry . March . March's Advanced Organic Chemistry . John Wiley & Sons . 2007 . 6th . 978-0-471-72091-1 . 1816.
4. . 25 . 32 . 1984 . 3415–3418 . A general procedure for mild and rapid reduction of aliphatic and aromatic nitro compounds using ammonium formate as a catalytic hydrogen transfer agent . Siya . Ram . Richard E. . Ehrenkaufer . 10.1016/S0040-4039(01)91034-2 . 2027.42/25034 . free.
5. Smith. Amos B.. Zhu. Wenyu. Shirakami. Shohei. Sfouggatakis. Chris. Doughty. Victoria A.. Bennett. Clay S.. Sakamoto. Yasuharu. 2003-03-01. Total Synthesis of (+)-Spongistatin 1. An Effective Second-Generation Construction of an Advanced EF Wittig Salt, Fragment Union, and Final Elaboration. Organic Letters. 5. 5. 761–764. 10.1021/ol034037a. 1523-7060. 12605509.
6. 10.15227/orgsyn.051.0082. Dehydroxylation of Phenols; Hydrogenolysis of Phenolic Ethers: Biphenyl. Organic Syntheses. 1971. 51. 82. Walter J. . Musliner. John W. . Gates, Jr.
7. Liebeskind. Lanny S.. Peña-Cabrera. Eduardo. Stille couplings catalyzed by palladium-on-carbon with CuI as a co-catalyst: synthesis of 2-(4'-Acetylhenyl)thiophene. Organic Syntheses. 2000. 77. 138. 10.15227/orgsyn.077.0135.
8. Mozingo. Ralph. Palladium catalysts. Organic Syntheses. 1946. 26. 77–82. 10.15227/orgsyn.026.0077. 20280763.