Tetrakis(triphenylphosphine)palladium(0)

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Tetrakis(triphenylphosphine)palladium(0)
3D model of the tetrakis(triphenylphosphine)palladium(0) molecule
Tetrakis(triphenylphosphine)palladium(0)
Identifiers
CAS number 14221-01-3 YesY
PubChem 11979704
RTECS number Unregistered
Properties
Molecular formula C72H60P4Pd
Molar mass 1,155.56 g mol−1
Appearance Bright yellow crystals
Melting point decomposes around 115 °C
Solubility in water Insoluble
Structure
Coordination
geometry
four triphenylphosphine monodentate
ligands attached to a central Pd(0)
atom in a tetrahedral geometry
Molecular shape tetrahedral
Dipole moment 0 D
Hazards
R-phrases n/a
S-phrases S22, S24/25
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity (yellow): no hazard code Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related complexes chlorotris(triphenylphosphine)rhodium(I)
tris(dibenzylideneacetone)dipalladium(0)
Related compounds triphenylphosphine
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Tetrakis(triphenylphosphine)palladium(0) is the chemical compound Pd[P(C6H5)3]4, often abbreviated Pd(PPh3)4, or even PdP4. It is a bright yellow crystalline solid that becomes brown upon decomposition in air.

Structure and properties[edit]

The four phosphorus atoms are at the corners of a tetrahedron surrounding the palladium(0) center. This structure is typical for four-coordinate 18e complexes.[1] The corresponding complexes Ni(PPh3)4 and Pt(PPh3)4 are also well known. Such complexes reversibly dissociate PPh3 ligands in solution, so reactions attributed to Pd(PPh3)4 often in fact arise from Pd(PPh3)3 or even Pd(PPh3)2.

Preparation[edit]

Tetrakis(triphenylphosphine)palladium(0) was first prepared by Lamberto Malatesta et al in the 1950s by reduction of sodium chloropalladate with hydrazine in the presence of the phosphine.[2] It is commercially available, but can be prepared in two steps from Pd(II) precursors:

PdCl2 + 2 PPh3 → PdCl2(PPh3)2
PdCl2(PPh3)2 + 2 PPh3 + 2.5 N2H4 → Pd(PPh3)4 + 0.5 N2 + 2 N2H5+Cl-

Both steps may be carried out in a one-pot reaction, without isolating and purifying the PdCl2(PPh3)2 intermediate.[3] Reductants other than hydrazine can be employed. The compound is sensitive to air, but can be purified by washing with methanol to give the desired yellow powder. It is usually stored cold under argon.

Applications[edit]

Pd(PPh3)4 is widely used as a catalyst for palladium-catalyzed coupling reactions.[4] Prominent applications include the Heck reaction, Suzuki coupling, Stille coupling, Sonogashira coupling, and Negishi coupling. These processes begin with two successive ligand dissociations followed by the oxidative addition of an aryl halide to the Pd(0) center:

Pd(PPh3)4 + ArBr → PdBr(Ar)(PPh3)2 + 2 PPh3

References[edit]

  1. ^ C. Elschenbroich, A. Salzer ”Organometallics : A Concise Introduction” (2nd Ed) (1992) Wiley-VCH: Weinheim. ISBN 3-527-28165-7
  2. ^ L. Malatesta and M. Angoletta, "Palladium(0) compounds. Part II. Compounds with triarylphosphines, triaryl phosphites, and triarylarsines" J. Chem. Soc., 1186 (1957). doi:10.1039/JR9570001186
  3. ^ D. R. Coulson; Satek, L. C.; Grim, S. O. (1972). "Tetrakis(triphenylphosphine)palladium(0)". Inorg. Synth. Inorganic Syntheses 13: 121. doi:10.1002/9780470132449.ch23. ISBN 978-0-470-13244-9. 
  4. ^ P. W. van Leeuwen (2005). Homogeneous Catalysis: Understanding the Art. Springer. ISBN 1-4020-3176-9.