Bis(triphenylphosphine)palladium chloride explained

Bis(triphenylphosphine)palladium chloride is a coordination compound of palladium containing two triphenylphosphine and two chloride ligands. It is a yellow solid that is soluble in some organic solvents. It is used for palladium-catalyzed coupling reactions, e.g. the Sonogashira–Hagihara reaction. The complex is square planar. Many analogous complexes are known with different phosphine ligands.

Preparation and reactions

This compound may be prepared by treating palladium(II) chloride with triphenylphosphine:^{[1] [2]}

PdCl₂ + 2 PPh₃ → PdCl₂(PPh₃)₂Upon reduction with hydrazine in the presence of excess triphenylphosphine, the complex is a precursor to tetrakis(triphenylphosphine)palladium, Pd(PPh₃)₄:^[3]

2 PdCl₂(PPh₃)₂ + 4 PPh₃ + 5 N₂H₄ → 2 Pd(PPh₃)₄ + N₂ + 4 N₂H₅⁺Cl⁻

Structure

Several crystal structures containing PdCl₂(PPh₃)₂ have been reported. In all of the structures, PdCl₂(PPh₃)₂ adopts a square planar coordination geometry and the trans isomeric form.^{[4] [5] [6] [7]}

Applications

The complex is used as a pre-catalyst for a variety of coupling reactions.^[8] The Suzuki reaction was once limited by high levels of catalyst and the limited availability of boronic acids. Replacements for halides were also found, increasing the number of coupling partners for the halide or pseudohalide as well. Using bis(triphenylphosphine)palladium chloride as the catalyst, triflates and boronic acids have been coupled on an 80 kilogram scale in good yield.^[9] The same catalyst is effective for the Sonogashira coupling.^[10]

See also

• Bis(triphenylphosphine)platinum(II) chloride
• Bis(triphenylphosphine)nickel(II) chloride

References

1. Palladium-Catalyzed Reaction of 1-Alkenylboronates with Vinylic Halides: (1Z,3E)-1-Phenyl-1,3-octadiene . Organic Syntheses . 68 . 130 . Norio Miyaura . Norio Miyaura. Akira Suzuki (chemist). Akira Suzuki . 1990 . 10.15227/orgsyn.068.0130.
2. Homogeneous Catalysis in the Reactions of olefinic Substances. V.Hydrogenation of Soybean Oil Methyl Ester with Triphenylphosphine and Triphenylarsine Palladium Catalysts. 44 . 147 . Hiroshi Itatani . J.C.Bailar . 1967 . Journal of the American Oil Chemists' Society. 10.1007/BF02558176. 93580917 .
3. Book: . 13 . 121–124 . Tetrakis(triphenylphosphine)palladium(0) . D. R. Coulson . Inorganic Syntheses . 10.1002/9780470132449.ch23 . 1972. 978-0-470-13244-9 .
4. Acta Crystallogr.. 1982. B38. 10. 2679–2681. 10.1107/S0567740882009583. trans-Dichlorobis(triphenylphosphine)palladium(II). G. Ferguson . R. McCrindle . A. J. McAlees . M. Parvez .
5. . 62 . 2006 . m1324–m1325 . trans-Dichlorobis(triphenylphosphine)palladium(II) dichloromethane solvate . G. Steyl . 6 . 10.1107/S1600536806017521 .
6. . 64 . 2008 . m621 . trans-Dichloridobis(triphenylphosphine)palladium(II) . J. Pons . J. García-Antón . X. Solans . M. Font-Bardia . J. Ros . Pt 5 . 10.1107/S1600536808008337 . 21202176 . 2961313 . free .
7. . 841 . 2017 . 31–38 . Crystal structure of a novel polymorph of trans-dichlorobis (triphenylphosphine) palladium (II) and its application as a novel, efficient and retrievable catalyst for the amination of aryl halides and stille cross-coupling reactions . A. Naghipour . . H. Babaee . M. Hashemi . B. Notash . 10.1016/j.jorganchem.2016.10.002 .
8. One-Pot Procedure for the Synthesis of Unsymmetrical Diarylalkynes . 75 . 10 . 3518–352 . René Severin . Jessica Reimer . Sven Doye . 2010 . J. Org. Chem. . 10.1021/jo100460v. 20420397 .
9. Jacks, T. E. . Belmont, Daniel T. . Briggs, Christopher A. . Horne, Nicole M. . Kanter, Gerald D. . Karrick, Greg L. . Krikke, James J. . McCabe, Richard J. . Mustakis, Jason G. . Nanninga, Thomas N.. 2004. Development of a Scalable Process for CI-1034, an Endothelin Antagonist. Organic Process Research & Development. 8. 2. 201–212. 10.1021/op034104g.
10. Chinchilla, R. . Nájera, C.. 2007. The Sonogashira Reaction: A Booming Methodology in Synthetic Organic Chemistry. Chem. Rev.. 107. 3. 874–922. 10.1021/cr050992x. 17305399.