Tetrakis(triphenylphosphine)palladium(0)

| Section3 = | Section7 = | Section8 = }}

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.

Preparation, structure, and properties

This complex is 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^-

Reductants other than hydrazine can be employed.

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. 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.

If the tetrakis(triphenylphosphine)palladium (0) is an orange brown, triturate with methanol and filter to give the desired yellow powder. Store under nitrogen in the fridge.

Applications

Pd(PPh₃)₄ is widely used as a catalyst for coupling reactions. Prominent applications include the Heck reaction and Suzuki coupling. These processes begin with the oxidative addition of an aryl halide to the Pd(0) center:

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

References

External links

• ChemExper Chemicals database
• Science lab product sheet
• D.R. Coulson, Tetrakis(triphenylphosphine)palladium(0), Inorg. Synth., No 21