|Jmol-3D images||Image 1|
|Molar mass||224.50 g/mol|
|Appearance||Brown yellow solid|
|Melting point||205 °C (478 K), decomposes|
|Solubility in water||low|
|Dipole moment||0 D|
|Main hazards||considered nonhazardous|
|Other anions||Palladium(II) chloride|
|Other cations||Platinum(II) acetate|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Palladium(II) acetate is a chemical compound of palladium described by the formula Pd(O2CCH3)2 or Pd(OAc)2. It is considered more reactive than the analogous platinum compound. It is soluble in many organic solvents.
As prepared by Wilkinson and coworkers in 1965, and later studied 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. Its structure was determined to be trimeric, consisting of an equilateral triangle of Pd atoms each pair of which is bridged with two acetate groups in a butterfly conformation. Each metal atom achieves approximate square planar co-ordination.
On the other hand, palladium(II) acetate prepared in a slightly different way was isolated as a pale pink powder, whose structure was determined by X-ray powder diffraction to consist of infinite chains in which the coordination geometry around each Pd is true square planar.
- Pd + 4 HNO3 → Pd(NO3)2 + 2 NO2 + 2 H2O
- Pd(NO3)2 + 2 CH3COOH → Pd(O2CCH3)2 + 2 HNO3
Palladium(II) propionate is prepared analogously; other carboxylates are prepared by reacting palladium(II) acetate with the appropriate carboxylic acid.
When warmed with alcohols, or on prolonged boiling with other solvents, palladium(II) acetate decomposes to palladium.
Palladium acetate is a catalyst for many organic reactions by combining with many common classes of organic compounds such as alkenes, dienes, and alkyl, aryl, and vinyl halides to form reactive adducts. Alkenes and π-allyl coordination to palladium(II) acetate involves sigma-type donation from the pi orbital of the alkene or π-allyl with concomitant pi-backbonding into an empty pi* orbital on the alkene or π-allyl. The greater the sigma donation to the metal is, the greater the pi-backbonding. The greater the pi-backbonding is, the greater the reduction in the bond order of the alkene or π-allyl. Reduction of the alkenes or π-allyl by coordination to palladium(II) acetate reverses the reactivity of the organic ligand allowing them to undergo reactions with nucleophiles rather than electrophiles.
Examples of palladium(II) acetate catalyzed reactions are:
- Vinylation: An example is the Heck reaction
- Rearrangement of Acyclic Dienes: An example is the Cope reaction
- Carbonylation reactions: for example, the formation of esters from aryl iodides by addition of carbon monoxide and an alcohol or phenol.
- Reductive amination of aldehydes or ketones using potassium formate.
- Wacker process: the oxidation of ethylene in water to form acetaldehyde (precursor to poly(vinyl acetate), a common glue).
- Buchwald-Hartwig amination of aryl halides/pseudohalides with alkyl an aryl amines.
Pd(O2CCH3)2 converts aryl bromides into aryltrimethylsilanes, an important 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.
Precursor to other Pd compounds
Palladium acetate is used to produce other palladium(II) compounds. For example, phenylpalladium acetate, used to isomerize allylic alcohols to aldehydes, is prepared by the following reaction:
- Hg(C6H5)(CH3COO) + Pd(CH3COO)2 → Pd(C6H5)(O2CCH3) + Hg(O2CCH3)2
Light or heat reduce palladium acetate to give thin layers of palladium and can produce nanowires and colloids.
- 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.
- 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.
- Kirik, S.D.; Mulagaleev, S.F.; Blokhin, A.I. (2004). Acta Cryst. C: m449–m450. doi:10.1107/S0108270104016129.
- 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.
- "High Purity Homogeneous Catalyst." Engelhard. Sept. 2005. Engelhard Corp. 24 Feb. 2006.<http://www.engelhard.com/documents/High%20Purity%20Homo%20Cat%20_Pd-acetate_%20A4%20Revised%20Final.pdf>.
- Toreki, R. "Allyl Ligands." The Organometallic HyperTextBook. 20 Nov. 2003. Chemglass. 01 Apr. 2006<http://www.ilpi.com/organomet/allyl.html>.
- Suggs, J W. "Palladium: Organometallic Chemistry." Encyclopedia of Inorganic Chemistry. Ed. R B. King. 8 vols. Chichester: Wiley, 1994.
- 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.
- 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.
- "Buchwald-Hartwig Cross Coupling Reaction". Organic Chemistry Portal.
- 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>.
- Richard F. Heck, "Aldehydes from Allylic Alcohols and Phenylpalladium Acetate: 2-Methyl-3-Phenylpropionaldehyde", Org. Synth.; Coll. Vol. 6: 815