Alfred Werner

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Alfred Werner
Alfred Werner ETH-Bib Portr 09965.jpg
Born 12 December 1866
Mulhouse, Haut-Rhin, Alsace, France
Died 15 November 1919(1919-11-15) (aged 52)
Zurich, Switzerland
Nationality Swiss
Alma mater University of Zurich
ETH Zurich
Known for configuration of transition metal complexes
Awards Nobel Prize for Chemistry (1913)
Scientific career
Fields Inorganic chemistry
Institutions University of Zurich
Doctoral advisor Arthur Rudolf Hantzsch, Marcellin Berthelot [ citation needed ]

Alfred Werner (12 December 1866 15 November 1919) was a Swiss chemist who was a student at ETH Zurich and a professor at the University of Zurich. He won the Nobel Prize in Chemistry in 1913 for proposing the octahedral configuration of transition metal complexes. Werner developed the basis for modern coordination chemistry. He was the first inorganic chemist to win the Nobel prize, and the only one prior to 1973. [1]

Switzerland federal republic in Western Europe

Switzerland, officially the Swiss Confederation, is a country situated in western, central and southern Europe. It consists of 26 cantons, and the city of Bern is the seat of the federal authorities. The sovereign state is a federal republic bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland is a landlocked country geographically divided between the Alps, the Swiss Plateau and the Jura, spanning a total area of 41,285 km2 (15,940 sq mi). While the Alps occupy the greater part of the territory, the Swiss population of approximately 8.5 million people is concentrated mostly on the plateau, where the largest cities are to be found: among them are the two global cities and economic centres Zürich and Geneva.

Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.

ETH Zurich Swiss Federal Institute of Technology in Zurich

ETH Zurich is a science, technology, engineering and mathematics university in the city of Zürich, Switzerland. Like its sister institution EPFL, it is an integral part of the Swiss Federal Institutes of Technology Domain that is directly subordinate to Switzerland's Federal Department of Economic Affairs, Education and Research. The school was founded by the Swiss Federal Government in 1854 with the stated mission to educate engineers and scientists, serve as a national center of excellence in science and technology and provide a hub for interaction between the scientific community and industry.

Contents

Biography

Werner was born in 1866 in Mulhouse, Alsace (which was then part of France, but which was annexed by Germany in 1871). He was raised as Roman Catholic. [2] He went to Switzerland to study chemistry at the Swiss Federal Institute (Polytechnikum) in Zurich where he obtained his doctorate in 1890 at the same institution.[ citation needed ] After postdoctoral study in Paris, he returned to the Swiss Federal Institute to teach (1892), in 1893 he moved to the University of Zurich where he became a professor in 1895. The same year he became a Swiss citizen.

Mulhouse Subprefecture and commune in Grand Est, France

Mulhouse is a city and commune in eastern France, close to the Swiss and German borders.

Alsace Place in Grand Est, France

Alsace is a cultural and historical region in eastern France, on the west bank of the upper Rhine next to Germany and Switzerland.

France Republic with mainland in Europe and numerous oversea territories

France, officially the French Republic, is a country whose territory consists of metropolitan France in Western Europe and several overseas regions and territories. The metropolitan area of France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean. It is bordered by Belgium, Luxembourg and Germany to the northeast, Switzerland and Italy to the east, and Andorra and Spain to the south. The overseas territories include French Guiana in South America and several islands in the Atlantic, Pacific and Indian oceans. The country's 18 integral regions span a combined area of 643,801 square kilometres (248,573 sq mi) and a total population of 67.3 million. France, a sovereign state, is a unitary semi-presidential republic with its capital in Paris, the country's largest city and main cultural and commercial centre. Other major urban areas include Lyon, Marseille, Toulouse, Bordeaux, Lille and Nice.

Research

Coordination chemistry

In 1893, Werner was the first to propose correct structures for coordination compounds containing complex ions, in which a central transition metal atom is surrounded by neutral or anionic ligands.

For example, it was known that cobalt forms a "complex" hexamminecobalt(III) chloride, with formula CoCl3•6NH3, but the nature of the association indicated by the dot was mysterious. Werner proposed the structure [Co(NH3)6]Cl3, with the Co3+ ion surrounded by six NH3 at the vertices of an octahedron. The three Cl are dissociated as free ions, which Werner confirmed by measuring the conductivity of the compound in aqueous solution, and also by chloride anion analysis using precipitation with silver nitrate. Later, magnetic susceptibility analysis was also used to confirm Werner's proposal for the chemical nature of CoCl3•6NH3.

Conductivity (electrolytic) measure of ability of an electrolyte solution to conduct electricity

Conductivity of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is Siemens per meter (S/m).

Silver nitrate chemical compound

Silver nitrate is an inorganic compound with chemical formula AgNO
3
. This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called lunar caustic because silver was called luna by the ancient alchemists, who believed that silver was associated with the moon.

In electromagnetism, the magnetic susceptibility is a measure of how much a material will become magnetized in an applied magnetic field. Mathematically, it is the ratio of magnetization M to the applied magnetizing field intensity H. This allows a simple classification of most materials' response to an applied magnetic field into two categories: an alignment with the magnetic field, χ>0, called paramagnetism, or an alignment against the field, χ<0, called diamagnetism.

cis-[Co(NH3)4 Cl2] Cis-dichlorotetraamminecobalt(III).png
cis-[Co(NH3)4 Cl2]
trans-[Co(NH3)4 Cl2] Trans-dichlorotetraamminecobalt(III).png
trans-[Co(NH3)4 Cl2]

For complexes with more than one type of ligand, Werner succeeded in explaining the number of isomers observed. For example, he explained the existence of two tetrammine isomers, "Co(NH3)4Cl3", one green and one purple. Werner proposed that these are two geometric isomers of formula [Co(NH3)4Cl2]Cl, with one Cl ion dissociated as confirmed by conductivity measurements. The Co atom is surrounded by four NH3 and two Cl ligands at the vertices of an octahedron. The green isomer is "trans" with the two Cl ligands at opposite vertices, and the purple is "cis" with the two Cl at adjacent vertices.

Werner also prepared complexes with optical isomers, and in 1914 he reported the first synthetic chiral compound lacking carbon, known as hexol with formula [Co(Co(NH3)4(OH)2)3]Br6.

Chirality (chemistry) geometric property of some molecules and ions

Chirality is a geometric property of some molecules and ions. A chiral molecule/ion is non-superposable on its mirror image. The presence of an asymmetric carbon center is one of several structural features that induce chirality in organic and inorganic molecules. The term chirality is derived from the Ancient Greek word for hand, χεῖρ (kheir).

Hexol chemical compound

Hexol is the name for various salts of a coordination complex that has historical significance. The salts were the first synthetic non-carbon-containing chiral compounds. The sulfate salt has the formula {[Co(NH3)4(OH)2]3Co}(SO4)3.

Nature of valence

Before Werner, chemists defined the valence of an element as the number of its bonds without distinguishing different types of bond. However, in complexes such as [Co(NH3)6]Cl3 for example, Werner considered that the Co-Cl bonds correspond to a "primary" valence of 3 at long distance, while the Co-NH3 bonds which correspond to a "secondary" or weaker valence of 6 at shorter distance. This secondary valence of 6 he referred to as the coordination number which he defined as the number of molecules (here of NH3) directly linked to the central metal atom. In other complexes he found coordination numbers of 4 or 8.

On these views, and other similar views, in 1904 Richard Abegg formulated what is now known as Abegg's rule which states that the difference between the maximum positive and negative valence of an element is frequently eight. This rule was used later in 1916 when Gilbert N. Lewis formulated the “octet rule” in his cubical atom theory.

In modern terminology Werner's primary valence corresponds to the oxidation state, and his secondary valence is called coordination number. The Co-Cl bonds (in the above example) are now classed as ionic, and each Co-N bond is a coordinate covalent bond between the Lewis acid Co3+ and the Lewis base NH3.

Works

Related Research Articles

Coordination complex molecule or ion containing ligands covalently bonded to a central atom

In chemistry, a coordination complex consists of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those of transition metals, are coordination complexes. A coordination complex whose centre is a metal atom is called a metal complex.

<i>Cis</i>–<i>trans</i> isomerism term used in organic chemistry; in the context of chemistry, cis indicates that the functional groups are on the same side of the carbon chain while trans conveys that functional groups are on opposing sides of the carbon chain

Cistrans isomerism, also known as geometric isomerism or configurational isomerism, is a term used in organic chemistry. The prefixes "cis" and "trans" are from Latin: "this side of" and "the other side of", respectively. In the context of chemistry, cis indicates that the functional groups are on the same side of the carbon chain while trans conveys that functional groups are on opposing sides of the carbon chain. Cis-trans isomers are stereoisomers, that is, pairs of molecules which have the same formula but whose functional groups are rotated into a different orientation in three-dimensional space. It is not to be confused with EZ isomerism, which is an absolute stereochemical description, and only to be used with alkenes. In general, stereoisomers contain double bonds that do not rotate, or they may contain ring structures, where the rotation of bonds is restricted or prevented. Cis and trans isomers occur both in organic molecules and in inorganic coordination complexes. Cis and trans descriptors are not used for cases of conformational isomerism where the two geometric forms easily interconvert, such as most open-chain single-bonded structures; instead, the terms "syn" and "anti" would be used.

Inorganic chemistry deals with the synthesis and behavior of inorganic and organometallic compounds. This field covers all chemical compounds except the myriad organic compounds, which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, as there is much overlap in the subdiscipline of organometallic chemistry. It has applications in every aspect of the chemical industry, including catalysis, materials science, pigments, surfactants, coatings, medications, fuels, and agriculture.

Ligand molecule or functional group that binds or can bind to the central atom in a coordination complex

In coordination chemistry, a ligand is an ion or molecule 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 electron pairs. The nature of metal–ligand bonding can range from covalent to ionic. Furthermore, the metal–ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligands".

In chemistry isomerization is the process by which one molecule is transformed into another molecule which has exactly the same atoms, but the atoms have a different arrangement e.g. A-B-C → B-A-C. In some molecules and under some conditions, isomerization occurs spontaneously. Many isomers are roughly equal in bond energy, and so exist in roughly equal amounts, provided that they can interconvert somewhat freely; that is, the energy barrier between the two isomers is not too high. When the isomerization occurs intramolecularly it is considered a rearrangement reaction.

In chemistry, the valence or valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. The concept of valence developed in the second half of the 19th century and helped successfully explain the molecular structure of inorganic and organic compounds. The quest for the underlying causes of valence led to the modern theories of chemical bonding, including the cubical atom (1902), Lewis structures (1916), valence bond theory (1927), molecular orbitals (1928), valence shell electron pair repulsion theory (1958), and all of the advanced methods of quantum chemistry.

Linkage isomerism is the existence of coordination compounds that have the same composition differing with the connectivity of the metal to a ligand.

Cyanate salt or ester of cyanic acid

The cyanate ion is the anion with the chemical formula written as [OCN] or [NCO]. In aqueous solution it acts as a base, forming isocyanic acid, HNCO. The cyanate ion is an ambidentate ligand, forming complexes with a metal ion in which either the nitrogen or oxygen atom may be the electron-pair donor. It can also act as a bridging ligand. Organic cyanates are called isocyanates when there is a C−NCO bond and cyanates when there is a C−OCN bond.

Octahedral molecular geometry

In chemistry, octahedral molecular geometry describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The octahedron has eight faces, hence the prefix octa. The octahedron is one of the Platonic solids, although octahedral molecules typically have an atom in their centre and no bonds between the ligand atoms. A perfect octahedron belongs to the point group Oh. Examples of octahedral compounds are sulfur hexafluoride SF6 and molybdenum hexacarbonyl Mo(CO)6. The term "octahedral" is used somewhat loosely by chemists, focusing on the geometry of the bonds to the central atom and not considering differences among the ligands themselves. For example, [Co(NH3)6]3+, which is not octahedral in the mathematical sense due to the orientation of the N-H bonds, is referred to as octahedral.

Metal ammine complex class of chemical compounds

In coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia (NH3) ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelt with a single "m". Almost all metal ions bind ammonia as a ligand, but the most prevalent examples of ammine complexes are for Cr(III), Co(III), Ni(II), Cu(II) as well as several platinum group metals.

The term coordination geometry is used in a number of related fields of chemistry and solid state chemistry/physics.

Square planar molecular geometry

The square planar molecular geometry in chemistry describes the stereochemistry that is adopted by certain chemical compounds. As the name suggests, molecules of this geometry have their atoms positioned at the corners of a square on the same plane about a central atom.

Inner sphere or bonded electron transfer is a redox chemical reaction that proceeds via a covalent linkage—a strong electronic interaction—between the oxidant and the reductant reactants. In Inner Sphere (IS) electron transfer (ET), a ligand bridges the two metal redox centers during the electron transfer event. Inner sphere reactions are inhibited by large ligands, which prevent the formation of the crucial bridged intermediate. Thus, IS ET is rare in biological systems, where redox sites are often shielded by bulky proteins. Inner sphere ET is usually used to describe reactions involving transition metal complexes and most of this article is written from this perspective. However, redox centers can consist of organic groups rather than metal centers.

Hexamminecobalt(III) chloride chemical compound

Hexaamminecobalt(III) chloride is the chemical compound with the formula [Co(NH3)6]Cl3. It is the chloride salt of the coordination complex [Co(NH3)6]3+, which is considered an archetypal "Werner complex", named after the pioneer of coordination chemistry, Alfred Werner. The cation itself is a metal ammine complex with six ammonia ligands attached to the cobalt(III) ion.

In chemistry, crystallography, and materials science the 'coordination number', also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ion/molecule/atom is called a ligand. This number is determined somewhat differently for molecules than for crystals.

Coordination isomerism is a form of structural isomerism in which the composition of the complex ion varies. In a coordination isomer the total ratio of ligand to metal remains the same, but the ligands attached to a specific metal ion change. Examples of a complete series of coordination isomers require at least two metal ions and sometimes more.

Creutz–Taube complex chemical compound

The Creutz–Taube ion is the metal complex with the formula [Ru(NH3)5]2(C4H4N2)5+. This cationic species has been heavily studied in an effort to understand the intimate details of inner sphere electron transfer, that is, how electrons move from one metal complex to another. The ion is named after Carol Creutz, who first prepared the complex, and her thesis advisor Henry Taube, who received a Nobel Prize in Chemistry for this and related discoveries on electron-transfer.

Tris(ethylenediamine)cobalt(III) chloride chemical compound

Tris(ethylenediamine)cobalt(III) chloride is a inorganic compound with the formula [Co(en)3]Cl3 (where "en" is the abbreviation for ethylenediamine). It is the chloride salt of the coordination complex [Co(en)3]3+. This trication was important in the history of coordination chemistry because of its stability and its stereochemistry. Many different salts have been described. The complex was first described by Alfred Werner who isolated this salt as yellow-gold needle-like crystals.

Chloropentamminecobalt chloride chemical compound

Chloropentamminecobalt chloride is the dichloride salt of the coordination complex [Co(NH3)5Cl]2+. It is a red-violet, diamagnetic, water-soluble salt. The compound has been of academic and historical interest.

Trans-dichlorodiammineplatinum(II)

Trans-dichlorodiammineplatinum(II) is the trans isomer of the coordination complex with the formula trans-PtCl2(NH3)2, sometimes called transplatin. It is a yellow solid with low solubility in water but good solubility in DMF. The existence of two isomers of PtCl2(NH3)2 led Alfred Werner to propose square planar molecular geometry.

References

  1. https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1913/werner-bio.html Nobel Prize Retrieved 1 december 2012
  2. "Alfred Werner - Swiss chemist". britannica.com. Retrieved 14 April 2018.