Palladium(II) acetate

Palladium(II) acetate
Names
IUPAC name
Palladium(II) acetate
Other names
Palladium diacetate
hexakis(acetato)tripalladium
bis(acetato)palladium
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.020.151
RTECS number AJ1900000
Properties
Pd(CH3COO)2
Molar mass 224.50 g/mol
Appearance Brown yellow solid
Density 2.19 g/cm3
Melting point 205 °C (401 °F; 478 K) decomposes
Boiling point decomposes
low
Structure
monoclinic
square planar
0 D
Hazards
Main hazards considered nonhazardous
Safety data sheet
R-phrases (outdated) 41
S-phrases (outdated) 24/25
Related compounds
Other anions
 Palladium(II) chloride
Other cations
 Platinum(II) acetate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Palladium(II) acetate is a chemical compound of palladium described by the formula [Pd(O2CCH3)2]n, abbreviated [Pd(OAc)2]n. It is more reactive than the analogous platinum compound. Depending on the value of n, the compound is soluble in many organic solvents and is commonly used as a catalyst for organic reactions.

Structure

With a 1:2 stoichiometric ratio of palladium atoms and acetate ligands, the compound exists as molecular and polymeric forms. Pd achieves approximate square planar coordination in both forms.

As prepared by Wilkinson and coworkers in 1965 and later characterized by Skapski and Smart in 1970 by single crystal X-ray diffraction, palladium(II) acetate is a red-brown solid that crystallizes as monoclinic plates. It has a trimeric structure, consisting of an equilateral triangle of Pd atoms each pair of which is bridged with two acetate groups in a butterfly conformation.[1][2]

Palladium(II) acetate can also be prepared as a pale pink form. According to X-ray powder diffraction, this form is polymeric.[3]

Preparation

Palladium acetate, in trimeric form, can be prepared by treating palladium sponge with a mixture of acetic acid and nitric acid. An excess of palladium sponge metal or nitrogen gas flow are required to prevent contamination by the mixed nitrito-acetate (Pd3(OAc)5NO2).[4][5]

Pd + 4 HNO3 → Pd(NO3)2 + 2 NO2 + 2 H2O
Pd(NO3)2 + 2 CH3COOH → Pd(O2CCH3)2 + 2 HNO3

Relative to the trimeric acetate, the mixed nitrate-acetate variant has different solubility and catalytic activity. Preventing, or controlling for the amount of, this impurity can be an important aspect for reliable use of palladium(II) acetate.[6]

Palladium(II) propionate is prepared analogously; other carboxylates are prepared by treating palladium(II) acetate with the appropriate carboxylic acid.[1] Likewise, palladium(II) acetate can be prepared by treating other palladium(II) carboxylates with acetic acid. This ligand exchange starting with a purified other carboxylate is an alternative way to synthesize palladium(II) acetate free from the nitro contaminant.[6]

When warmed with alcohols, or on prolonged boiling with other solvents, palladium(II) acetate decomposes to palladium.[1]

Catalysis

Palladium acetate is a catalyst for many organic reactions, especially alkenes, dienes, and alkyl, aryl, and vinyl halides to form reactive adducts.[7]

Reactions catalyzed by palladium(II) acetate:

  • Vinylation: An example is the Heck reaction and related processes.[8]
  • Rearrangement of acyclic dienes: An example is the Cope rearrangement
  • Carbonylation reactions: for example, the formation of esters from aryl iodides, carbon monoxide, an alcohol or phenol.[9]
  • Reductive amination of aldehydes or ketones by potassium formate.[10]
  • Wacker process: the oxidation of ethylene by water to acetaldehyde (precursor to poly(vinyl acetate).
  • Buchwald-Hartwig amination of aryl halides/pseudohalides with alkyl an aryl amines.[11][12]
  • conversion of aryl bromides into the trimethylsilanes, a functional group in many organic compounds including the fungicide "Latitude".
RC6H4Br + Si2(CH3)6 → RC6H4Si(CH3)3 + Si(CH3)3Br

Pd(O2CCH3)2 is compatible with the electronic properties of aryl bromides, and unlike other methods of synthesis, this method does not require high pressure equipment.[13]

Precursor to other Pd compounds

Palladium acetate is used to produce other palladium(II) compounds. For example, phenylpalladium acetate, used to isomerize allyl alcohols to aldehydes, is prepared by the following reaction:[14]

Hg(C6H5)(OAc) + Pd(OAc)2 → Pd(C6H5)(OAc) + Hg(OAc)2

Palladium(II) acetate reacts with acetylacetone (the "acac" ligand) to produce Pd(acac)2.

Light or heat reduce palladium acetate to give thin layers of palladium and can produce nanowires and colloids.[4]

See also

References

  1. 1 2 3 T. A. Stephenson; S. M. Morehouse; A. R. Powell; J. P. Heffer and G. Wilkinson (1965). "667. Carboxylates of palladium, platinum, and rhodium, and their adducts". Journal of the Chemical Society (Resumed): 3632. doi:10.1039/jr9650003632.
  2. ↑ Skapski, A C.; M. L. Smart (1970). "The Crystal Structure of Trimeric Palladium(II) Acetate". J. Chem. Soc. D (11): 658b–659. doi:10.1039/C2970000658b.
  3. ↑ Kirik, S.D.; Mulagaleev, S.F.; Blokhin, A.I. (2004). "[Pd(CH 3 COO) 2 ] n from X-ray powder diffraction data". Acta Crystallogr. C. 60 (9): m449–m450. doi:10.1107/S0108270104016129.
  4. 1 2 Bakhmutov, V. I.,; Berry, J. F.; Cotton, F. A.; Ibragimov, S.; Murillo, C. A. (2005). "Non-Trivial Behavior of Palladium(II) Acetate". Dalton Transactions (11): 1989–1992. doi:10.1039/b502122g. PMID 15909048.
  5. ↑ "High Purity Homogeneous Catalyst" (PDF). Engelhard. September 2005. Archived from the original (PDF) on 17 March 2006. Retrieved 24 February 2006.
  6. 1 2 Ritter, Stephen K. (May 2, 2016). "Chemists introduce a user's guide for palladium acetate". Chemical & Engineering News. 94 (18): 20–21.
  7. ↑ Suggs, J W. "Palladium: Organometallic Chemistry." Encyclopedia of Inorganic Chemistry. Ed. R B. King. 8 vols. Chichester: Wiley, 1994.
  8. ↑ Keary M. Engle, Navid Dastbaravardeh, Peter S. Thuy-Boun, Dong-Hui Wang, Aaron C. Sather, Jin-Quan Yu (2015). "Ligand-Accelerated ortho-C-H Olefination of Phenylacetic Acids". Org. Synth. 92: 58. doi:10.15227/orgsyn.092.0058. PMC 4936495.
  9. ↑ Nikitin, Kirill V.; Andryukhova, N.P.; Bumagin, N.A.; Beletskaya, I.P. (1991). "Synthesis of Aryl Esters by Pd-catalysed Carbonylation of Aryl Iodides". Mendeleev Communications. 1 (4): 129–131. doi:10.1070/MC1991v001n04ABEH000080.
  10. ↑ Basu, B., Satadru J., Mosharef H. B., and Pralay D. (2003). "A Simple Protocol for the Direct Reductive Amination of Aldehydes and Ketones Using Potassium Formate and Catalytic Palladium Acetate". ChemInform. 34 (30): 555–557. doi:10.1002/chin.200330069.
  11. ↑ Linli He, Shawn P. Allwein, Benjamin J. Dugan, Kyle W. Knouse, Gregory R. Ott, Craig A. Zificsak (2016). "Synthesis of α-Carboline". Org. Synth. 93: 272. doi:10.15227/orgsyn.093.0272.
  12. ↑ "Buchwald-Hartwig Cross Coupling Reaction". Organic Chemistry Portal.
  13. ↑ Gooben, L J. "Research Area "New Pd-Catalyzed Cross-Coupling Reactions"" 28 Feb. 2006<http://www.mpi-muelheim.mpg.de/kofo/bericht2002/pdf/2.1.8_gossen.pdf> Archived July 12, 2007, at the Wayback Machine..
  14. ↑ Richard F. Heck. "Aldehydes from Allylic Alcohols and Phenylpalladium Acetate: 2-Methyl-3-Phenylpropionaldehyde". Organic Syntheses. ; Collective Volume, 6, p. 815
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