Tetrakis(triphenylphosphine)palladium(0)

Tetrakis(triphenylphosphine)palladium(0)
IUPAC name

Tetrakis(triphenylphosphane)palladium(0)
Other names

TPP palladium(0)
Identifiers
CAS number 14221-01-3 Y
PubChem 11979704
RTECS number Unregistered
Properties
Molecular formula C72H60P4Pd
Molar mass 1155.56 g mol−1
Appearance Bright yellow crystals
Melting point

decomposes around 115 °C
Solubility in water Insoluble
Structure
Coordination
geometry		 four triphenylphosphine unidentate
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
1
2
0
Related compounds
Related complexes chlorotris(triphenylphosphine)rhodium(I)
tris(dibenzylideneacetone)dipalladium(0)
Related compounds triphenylphosphine
 Y (verify) (what is: Y/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.

Contents

Structure and properties

The four P 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, releasing the 16e M(PPh3)3. Thus, reactions attributed to Pd(PPh3)4 in fact arise from Pd(PPh3)3 or even Pd(PPh3)2.

Preparation

Tetrakis(triphenylphosphine)palladium(0) was first prepared by Lamberto Malatesta and his group in Milan in the 1960s 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 → cis-PdCl2(PPh3)2
cis-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 cis-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

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

  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 9780470132449. 
  4. ^ P. W. van Leeuwen (2005). Homogeneous Catalysis: Understanding the Art. Springer. ISBN 1-4020-3176-9.