[19978-61-1]  · C26H24Cl2P2Pd  · Dichloro[1,2-bis(diphenylphosphino)ethane]palladium(II)  · (MW 575.75)

(catalyst for carbonylation1 and biscarbonylation2,3 of aryl halides with amines)

Alternate Names: [1,2-bis(diphenylphosphino)ethane]palladium(II) chloride; dichloro[ethylenebis(diphenylphosphino)]palladium(II).

Physical Data: mp >300 °C.

Form Supplied in: orange powder; available from several suppliers.

Analysis of Reagent Purity: 1H NMR (CDCl3-DMSO-d6) d 3.5 (t, CH2), d 3.8 (q, CH2); 1H NMR (CDCl3) d 3.45 (t, CH2), d 3.6 (q, CH2); 31P NMR (121.5 MHz, CH2Cl2) 58.3 (s).

Preparative Methods: prepared by treating commercially available K2PdCl2 (in DMF) with bis(diphenylphosphino)ethane (in CH2Cl2).4,5 It can also prepared from K2PdCl2 (in H2O) and bis(diphenylphosphino)ethane (in CH2Cl2) using Bu4NCl (in CH2Cl2) as a phase-transfer catalyst.6

Purification: recrystallization from DMF-ether.

Handling, Storage, and Precautions: moisture sensitive.

N-Substituted Phthalimides.

The title reagent is useful in carbonylation and coupling of o-dihalo aromatics and primary amines to form N-substituted phthalimides.1 Optimal conditions for the reaction of o-diiodobenzene and aniline use DMA (0.2 M), 115 °C, 90 psi of CO, 3% PdCl2(dppe), and 2.4 equiv of DBU (eq 1). This procedure tolerates a wide variety of functional groups and gives a good yield of desired products. An exception is the reaction of aniline with 1,2-dibromocyclopentene under the above conditions, which has been reported to give a variety of products.

a-Keto Amides.

The title reagent is used as a catalyst to prepare a-keto amides and amides from aryl halides upon treatment with secondary amines and Carbon Monoxide (eq 2).2,3 These reactions are most commonly carried out without solvent at 100 °C at 10 atm of CO using a 1:3:0.1 molar ratio of aryl halide/secondary amine/PdCl2(dppe).

Allylation of Allylic Alcohols.

Allylation of carbonyl compounds is carried out via the formation of p-allylpalladium complexes using the title reagent as a catalyst and Tin(II) Chloride as a reducing agent (eq 3).7 The reactivity order of allylating agents is allylic carbonate > allylic alcohol > allylic acetate and that of carbonyl compounds is aldehyde > ketone. Polar solvents such as DMF, DMSO, or 1,3-Dimethyl-2-imidazolidinone (DMI) are preferred for higher regioselectivity.

Other Uses.

The title reagent is used as a catalyst for cross coupling of primary, secondary, and tertiary Grignard and alkylzinc reagents with organic halides, but results are reported to be unsatisfactory.8,9 Dichloro[1,1-bis(diphenylphosphino)ferrocene]palladium(II) [PdCl2(dppf)] is the preferred catalyst in the case of primary and secondary Grignard and alkyl zinc reagents,8 whereas 1,1-[bis(diphenylphosphino)ferrocene)]nickel(II) chloride is an effective catalyst in the case of tertiary alkyl Grignard reagents.9 Allylic p-tolyl sulfones are desulfonylated to the corresponding alkanes in moderate yield by Lithium Triethylborohydride in the presence of a catalytic amount of the title reagent under mild conditions with preservation of the original stereochemistry. Dichloro[1,3-bis(diphenylphosphino)propane]palladium(II) [PdCl2(dppp)] gives better results in the desulfonylation.10

Related Reagents.

PdCl2(PPh3)2 has shown similar results in carbonylation and coupling of o-dihalo aromatics and primary amines to form N-substituted phthalimides, but Palladium(II) Chloride, Palladium(II) Acetate, PdCl2.2MeCN, and PdCl2.2BzCN have shown inferior results.1 Dichlorobis(methyldiphenylphosphine)palladium(II) and PdCl2(PBuPh2)2 are reported to be more effective as catalysts among the palladium complexes containing tertiary phosphine ligands.2 Bis(benzonitrile)dichloropalladium(II) is a better catalyst for carbonyl allylation using allylic alcohols because of its stability towards air and moisture.7

1. Perry, R. J.; Turner, S. R. JOC 1991, 56, 6573.
2. Ozawa, F.; Soyama, H.; Yanagihara, H.; Aoyama, I.; Takino, H.; Izawa, K.; Yamamoto, T.; Yamamoto, A. JACS 1985, 107, 3235.
3. Ozawa, F.; Soyama, H.; Yamamoto, T.; Yamamoto, A. TL 1982, 23, 3383.
4. Park, Y.; Kim, K.; Cho, Y. J. Korean Chem. Soc. 1992, 36, 685 (CA 1993, 118, 88 272d).
5. Westland, A. D. JCS 1965, 3060.
6. Lin, I. J.; Liaw, M. D. S. J. Chin. Chem. Soc. 1993, 40, 451.
7. Takahara, J. P.; Masuyama, Y.; Kurusu, Y. JACS 1992, 114, 2577.
8. Hayashi, T.; Konishi, M.; Kobori, Y.; Kumuda, M.; Higuchi, T.; Hirotsu, K. JACS 1984, 106, 158.
9. Hayashi, T.; Konishi, M.; Yokota, K.; Kumuda, M. CL 1980, 767.
10. Mohri, M.; Kinoshita, H.; Inomata, K.; Kotake, H. CL 1985, 451.

Janak K. Padia

Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA

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