Dichlorobis(triphenylphosphine)nickel(II) refers to a pair of

metal phosphine complex A metal-phosphine complex is a In coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. P ...

es with the formula NiCl₂ (C₆H₅)₃sub>2. The compound exists as two isomers, a paramagnetic dark blue solid and a diamagnetic red solid. These complexes function as

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 ...

s for organic synthesis.Montgomery, J. Science of Synthesis Georg Thiene Verlag KG, Vol. 1, p 11, CODEN: SSCYJ9

Synthesis and structure

The blue isomer is prepared by treating hydrated nickel chloride with

triphenylphosphine Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists ...

in alcohols or glacial acetic acid: :NiCl₂•6H₂O + 2 PPh₃ → NiCl₂(PPh₃)₂ + 6 H₂O When allowed to crystallise from chlorinated solvents, the tetrahedral isomer converts to the square planar isomer. The square planar form is red and diamagnetic. The phosphine ligands are

trans Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of". Used alone, trans may refer to: Arts, entertainment, and media * Trans (festival), a former festival in Belfast, Northern Ireland, United Kingdom * ''Trans'' (fil ...

with respective Ni-P and Ni-Cl distances of 2.24 and 2.17 Å. The blue form is paramagnetic and features tetrahedral Ni(II) centers. In this isomer, the Ni-P and Ni-Cl distances are elongated at 2.32 and 2.21 Å. As illustrated by the title complexes, tetrahedral and square planar isomers coexist in solutions of various four-coordinated nickel(II) complexes. Weak field ligands, as judged by the

spectrochemical series A spectrochemical series is a list of ligands ordered by ligand "strength", and a list of metal ions based on oxidation number, group and element. For a metal ion, the ligands modify the difference in energy Δ between the d orbitals, called the l ...

, favor tetrahedral geometry and strong field ligands favor the square planar isomer. Both weak field (Cl⁻) and strong field (PPh₃) ligands comprise NiCl₂(PPh₃)₂, hence this compound is borderline between the two geometries.

Steric effect Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions ...

s also affect the equilibrium; larger ligands favoring the less crowded tetrahedral geometry.

Applications

The complex was first described by

Walter Reppe Walter Julius Reppe (29 July 1892 in Göringen – 26 July 1969 in Heidelberg) was a German chemist. He is notable for his contributions to the chemistry of acetylene. Education and career Walter Reppe began his study of the natural sciences ...

who popularized its use in

alkyne trimerisation In organic chemistry, an alkyne trimerisation is a +2+2nbsp; cycloaddition reaction in which three alkyne units () react to form a benzene ring. The reaction requires a metal catalyst. The process is of historic interest as well as being applic ...

s and

carbonylation Carbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry. The term carbony ...

s. Dichlorobis(triphenylphosphine)nickel(II) is a catalyst in

Suzuki reaction The Suzuki reaction is an organic reaction, classified as a cross-coupling reaction, where the coupling partners are a boronic acid and an organohalide and the catalyst is a palladium, palladium(0) complex. It was first published in 1979 by Akira ...

s, although usually inferior in terms of activity.

References

{{reflist Nickel complexes Triphenylphosphine complexes Chloro complexes

Synthesis and structure

Applications

See also

References