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Allyl palladium chloride dimer from an allyl chloride; Bis(Methallyl)di-chloro-dipalladium(II)

SyntheticPage 50
DOI: 10.1039/SP50
Submitted Aug 15, 2001, published Aug 15, 2001
Lisa Titcomb (lisa.titcomb@gmail.com)
A contribution from Caddick/Cloke Groups, Sussex


			Reaction Scheme: Allyl palladium chloride dimer from an allyl chloride

Chemicals Used

Palladium chloride (Strem),
Sodium chloride,
Methanol,
Methallyl chloride (Aldrich, isomeric mixture),
CO (Air products, technical grade).

Procedure

A 500 ml one necked round bottomed flask with a sidearm was fitted with a stir bar and charged with PdCl2 (4.44 g, 25 mmol), NaCl (2.96 g, 50 mmol), H2O (20 mL) and MeOH (60 mL). The mixture was stirred for 10 min to allow formation of an aqueous solution. Methallyl Chloride (7.10 g, 78 mmol) was added to the solution and a septum fitted to the flask. A needle, connected to a CO cylinder, was inserted into the septum and the tip placed in the solution. CO was bubbled through the solution and vented via a bubbler attached to the sidearm. The mixture was left to stir for 1 h during which time a colour change was observed from reddish brown to yellow as a flocculent yellow solid precipitated. The yellow suspension was poured into water (300 mL) and the product extracted with chloroform (3 x 100 mL). The chloroform extract was washed with water (3 x 50 mL) and dried over MgSO4. The solvent was removed in vacuo to yield a yellow solid which was recrystallized from a chloroform/hexane layered system to yield the product as a yellow, crystalline air stable solid. 4.12 g of product were obtained (84 % yield).

Author's Comments

This procedure works well and has been repeated 7 times. The reaction has been performed using anything from 2.22 g of PdCl2 to 6.66 g of PdCl2. It is important to obtain a solution before adding the methallyl chloride as this indicates formation of Na2PdCl4, the species needed in the next stage of the reaction. An excess of methallyl chloride is required for the procedure to work. Occasionally, after separation of the organic phase, a white solid persists in the chloroform layer. This is removed when the MgSO4 is filtered from the solution. A 1H nmr spectrum of the crude product shows impurities which are removed by recrystallisation. This procedure works equally well for the preparation of the allyl derivative allthough this compound appears to have a shorter shelf life than the methallyl derivative as evident by the formation of palladium metal after three months.

Data

1H nmr (C6D6): 1.38 (3H, s, CH3), 2.32 (2H, d) 3.41, (2H, d) (syn and anti terminal allyl H's)

Lead Reference

Tatsuno, Y.; Yoshida, T.; Otsuka, S. Inorg. Synth., John Wiley & Sons, 1990, 28, 342.

Other References

Tatsuno, Y.; Yoshida, T.; Otsuka, S. Inorg. Synth., John Wiley & Sons, 1979, 19, 220.

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Keywords: 50, allyl palladium chloride dimer, methallyl, palladium

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