Dichlorobis(triphenylphosphine)nickel(II) refers to a pair of
metal phosphine complexes with the formula NiCl
2 (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 increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
s for
organic synthesis
Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...
.
[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 in alcohols or glacial
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...
:
:NiCl
2•6H
2O + 2 PPh
3 → NiCl
2(PPh
3)
2 + 6 H
2O
When allowed to crystallise from chlorinated solvents, the
tetrahedral
In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tet ...
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:
Sociology
* Trans, a sociological term which may refer to:
** Transgender, people who identify themselves with a gender that di ...
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, favor tetrahedral geometry and strong field ligands favor the square planar isomer. Both weak field (Cl
−) and strong field (PPh
3) ligands comprise NiCl
2(PPh
3)
2, hence this compound is borderline between the two geometries.
Steric effects also affect the equilibrium; larger ligands favoring the less crowded tetrahedral geometry.
Applications
The complex was first described by
Walter Reppe who popularized its use in
alkyne trimerisations and
carbonylation
In chemistry, carbonylation refers to reactions that introduce carbon monoxide (CO) into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemis ...
s. Dichlorobis(triphenylphosphine)nickel(II) is a catalyst in
Suzuki reaction
The Suzuki reaction or Suzuki coupling is an organic reaction that uses a palladium complex catalyst to cross-couple a boronic acid to an organohalide. It was first published in 1979 by Akira Suzuki, and he shared the 2010 Nobel Prize in Chemi ...
s, although usually inferior in terms of activity.
See also
*
Bis(triphenylphosphine)palladium(II) chloride
*
Bis(triphenylphosphine)platinum(II) chloride
* Bis(tricyclohexylphosphine)nickel(II) chloride
*
Dichloro(1,2-bis(diphenylphosphino)ethane)nickel
References
{{reflist
Nickel complexes
Triphenylphosphine complexes
Chloro complexes