| Tetrakis(triphenylphosphine)palladium(0) | |
|---|---|
palladium(0)-3D-sticks.png) |
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palladium(0).jpg) |
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| IUPAC name |
Tetrakis(triphenylphosphane)palladium(0)
|
| Other names | TPP palladium(0) |
| Identifiers | |
| CAS number | 14221-01-3  |
| 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 |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 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.
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) is commercially available. It can be relatively inexpensive per unit weight, due to the low percentage weight of palladium.
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-
Both steps may be carried out in a one-pot reaction, without isolating and purifying the bis(triphenylphosphine)palladium(II) dichloride intermediate.[2] Reductants other than hydrazine can be employed. 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 freezer.
Another popular way of obtaining this compound is by displacement of the ligands of dbanPd (e.g. tris(dibenzylideneacetone)dipalladium(0)) with triphenylphosphine. Since the dba ligands are quite innocuous, these two compounds may be used as a one-for-one replacement in catalytic ractions:[3]
- dba2Pd + 4 PPh3 → Pd(PPh3)4 + 2 dba
Applications
Pd(PPh3)4 is widely used as a catalyst for palladium-catalyzed coupling reactions.[4] 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
- ^ C. Elschenbroich, A. Salzer ”Organometallics : A Concise Introduction” (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN 3-527-28165-7
- ^ D. R. Coulson (1972). "23. Tetrakis(triphenylphosphine)palladium(0)". Inorg. Synth. 13: 121. doi:.
- ^ A. Tenaglia and B. Waegell (1988). "Palladium-Catalyzed Reaction of 1,3-diene monoepoxides with sodium azide. 1,4-Azidohydroxylation of conjugated diene". Tetrahedron Letters 29 (38): 4851–4854. doi:.
- ^ P. W. van Leeuwen (2005). Homogeneous Catalysis: Understanding the Art. Springer. ISBN 1-4020-3176-9.
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