Zeise's salt on:
[Wikipedia]
[Google]
[Amazon]
Zeise's salt, potassium trichloro(ethylene)platinate(II) hydrate, 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 ...
with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
K
PtCl3(C2H4)">platinum.html" ;"title="/nowiki>platinum">PtCl3(C2H4)�H2O. The anion of this air-stable, yellow, coordination complex
A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...
contains an
''η''2-ethylene">hapticity">''η''
2-ethylene ligand">ethylene.html" ;"title="hapticity">''η''
2-ethylene">hapticity">''η''
2-ethylene ligand. The anion features a platinum atom with a square planar geometry. The salt is of historical importance in the area of
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
as one of the first examples of a transition metal alkene complex and is named for its discoverer,
William Christopher Zeise
William Christopher Zeise (15 October 1789 – 12 November 1847) was a Danish organic chemist. He is best known for synthesising one of the first organometallic compounds, named Zeise's salt in his honour. He also performed pioneering studie ...
.
Preparation
This compound is commercially available as a hydrate. The hydrate is commonly prepared from
K2 Potassium tetrachloroplatinate">K2catalytic
Catalysis () is the increase in reaction rate, 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 ...
amount of Tin(II) chloride">SnCl2. The water of hydration can be removed ''in vacuo''.
Structure
The alkene C=C bond is approximately perpendicular to the PtCl
3 plane. In Zeise's salt and related compounds, the alkene rotates about the metal-alkene bond with a modest activation energy. Analysis of the barrier heights indicates that the π-bonding between most metals and the alkene is weaker than the σ-bonding. In Zeise's anion, this rotational barrier has not been assessed.
History
Zeise's salt was one of the first
organometallic
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
compounds to be reported. It was discovered by
William Christopher Zeise
William Christopher Zeise (15 October 1789 – 12 November 1847) was a Danish organic chemist. He is best known for synthesising one of the first organometallic compounds, named Zeise's salt in his honour. He also performed pioneering studie ...
, a professor at the
University of Copenhagen
The University of Copenhagen (, KU) is a public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in Scandinavia, after Uppsala University.
...
, who prepared this compound in 1830 while investigating the reaction of
PtCl4 with boiling
ethanol
Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
. Following careful analysis he proposed that the resulting compound contained
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
.
Justus von Liebig
Justus ''Freiherr'' von Liebig (12 May 1803 – 18 April 1873) was a Germans, German scientist who made major contributions to the theory, practice, and pedagogy of chemistry, as well as to agricultural and biology, biological chemistry; he is ...
, a highly influential chemist of that era, often criticised Zeise's proposal, but Zeise's proposal was decisively supported in 1868 when Birnbaum prepared the complex using ethylene. Zeise's salt received a great deal of attention during the second half of the 19th century because chemists could not explain its
molecular structure
Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that det ...
. This question remained unanswered until the determination of its
X-ray crystal structure in the 20th century. Zeise's salt stimulated much scientific research in the field of
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
and would be key in defining new concepts in chemistry. The
Dewar–Chatt–Duncanson model explains how the metal is coordinated to the C=C double bond.
Related compounds
* Zeise's dimer,
''η''2-C2H4)PtCl2sub>2, derived from Zeise's salt by elimination of KCl followed by dimerisation.
* COD-platinum dichloride,
(cyclooctadiene)PtCl2, derived from
platinum(II) chloride and
1,5-cyclooctadiene, is a common platinum(II) alkene complex.
Many other ethylene complexes have been prepared. For example, ethylenebis(triphenylphosphine)platinum(0),
C6H5)3Psub>2Pt(H
2C=CH
2), wherein the platinum is three-coordinate and in
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
0 (Zeise's salt is a derivative of platinum(II)).
* Dichloro(ethylene)(α-
methylbenzylamine)platinum(II) (PtCl
2(C
2H
4)(PhCH(NH
2)Me) is a chiral derivative of Zeise's salt that is used for the
chiral resolution
Chiral resolution, or enantiomeric resolution, is a process in stereochemistry for the separation of racemic mixture into their enantiomers. It is an important tool in the production of optically active compounds, including drugs. Another term wit ...
of alkenes.
References
{{Platinum compounds
Organoplatinum compounds
Alkene complexes
Chlorides
Chloro complexes