Tetrakis(triphenylphosphine)palladium(0) (sometimes called quatrotriphenylphosphine palladium) is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

d(P(C₆H₅)₃)₄ often abbreviated Pd( PPh₃)₄, or rarely PdP₄. It is a bright yellow

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

solid that becomes brown upon decomposition in

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

Structure and properties

The four

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

atoms Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, an ...

are at the corners of a

tetrahedron In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...

surrounding the palladium(0) center. This structure is typical for four-coordinate 18 e⁻ complexes. The corresponding complexes Ni(PPh₃)₄ and Pt(PPh₃)₄ are also well known. Such complexes reversibly dissociate PPh₃

ligands In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electro ...

in solution, so reactions attributed to Pd(PPh₃)₄ often in fact arise from Pd(PPh₃)₃ or even Pd(PPh₃)₂.

Preparation

Tetrakis(triphenylphosphine)palladium(0) was first prepared by Lamberto Malatesta et al. in the 1950s by reduction of sodium chloropalladate with

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

in the presence of the

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

. 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 + N₂H₄ → Pd(PPh₃)₄ + N₂ + 2 N₂H₅Cl Both steps may be carried out in a

one-pot reaction In chemistry a one-pot synthesis is a strategy to improve the efficiency of a chemical reaction whereby a reactant is subjected to successive chemical reactions in just one reactor. This is much desired by chemists because avoiding a lengthy sepa ...

, without isolating and purifying the PdCl₂(PPh₃)₂ intermediate.

Reductant In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth meta ...

s other than hydrazine can be employed. The compound is sensitive to air, but can be purified by washing with

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

to give the desired yellow powder. It is usually stored cold under

argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...

Applications

Pd(PPh₃)₄ is widely used as a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

for

palladium-catalyzed coupling reaction In organic chemistry, a cross-coupling reaction is a reaction where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = organic fragment, M = ...

s. Prominent applications include the

Heck reaction The Heck reaction (also called the Mizoroki–Heck reaction) is the chemical reaction of an unsaturated halide (or triflate) with an alkene in the presence of a base and a palladium catalyst (or palladium nanomaterial-based catalyst) to form a s ...

, Suzuki coupling,

Stille coupling The Stille reaction is a chemical reaction widely used in organic synthesis. The reaction involves the coupling of two organic groups, one of which is carried as an organotin compound (also known as organostannanes). A variety of organic electroph ...

Sonogashira coupling The Sonogashira reaction is a cross-coupling reaction used in organic synthesis to form carbon–carbon bonds. It employs a palladium catalyst as well as copper co-catalyst to form a carbon–carbon bond between a terminal alkyne and an aryl or v ...

, and

Negishi coupling The Negishi coupling is a widely employed transition metal catalyzed cross-coupling reaction. The reaction couples organic halides or triflates with organozinc compounds, forming carbon-carbon bonds (C-C) in the process. A palladium (0) specie ...

. These processes begin with two successive ligand dissociations followed by the

oxidative addition Oxidative addition and reductive elimination are two important and related classes of reactions in organometallic chemistry. Oxidative addition is a process that increases both the oxidation state and coordination number of a metal centre. Oxidat ...

of an

aryl halide In organic chemistry, an aryl halide (also known as haloarene) is an aromatic compound in which one or more hydrogen atoms, directly bonded to an aromatic ring are replaced by a halide. The haloarene are different from haloalkanes because they exhi ...

to the Pd(0) center: :Pd(PPh₃)₄ + ArBr → PdBr(Ar)(PPh₃)₂ + 2 PPh₃

References

{{Palladium compounds Palladium compounds Reagents for organic chemistry Triphenylphosphine complexes Homogeneous catalysis