Werner, Alfred complexes

Transition metal complexes were intensively studied at the beginning of the 20 century. As Alfred Werner anticipated, complexes with the coordination number six are octahedral. (Coordination number is the number of ligands bonded to the central metal atom). Just as the tetrahedral configuration is most common in organic chemistry, so is the octahedral configuration the dominant structure of inorganic complexes. This is the reason why most attention is paid to the octahedral structure. 

It exists as optical isomers and was first resolved by Alfred Werner. The route to the bis complexes generates the ammine in situ and is applicable to other ammines (tren, trien, etc.) yielding principally the trans-isomer... 

The seminal studies on these complex compounds were conducted by Alfred Werner in an intensive period of work at the turn of the century. A typical example of the problems that Werner addressed lies in the various compounds which can be obtained containing cobalt, ammonia and chlorine. Stable and chemically distinct materials with formulations Co(NH3) Cl3 (n = 4,5 or 6) can be isolated. The concepts of valency and three-dimensional structure in carbon chemistry were being developed at that time, but it was apparent that the same rules could not apply to... 

C20-0115. In the 1890s, Alfred Werner prepared several platinum complexes that contained both ammonia and... 

Many ionic compounds contain what used to be referred to as water of crystallization . For example, magnesium chloride can exist as a fully hydrated salt which was formerly written MgCla.bHjO, but is more appropriately written Mg(OH2)eCl2, since the water molecules occupy coordination sites around the magnesium ions. This is typical. In most compounds that contain water of crystallization, the water molecules are bound to the cation in an aquo complex in the manner originally proposed by Alfred Werner (1866-1919) in 1893 (Kauffman, 1981). Such an arrangement has been confirmed in numerous cases by X-ray diffraction techniques. 

Alfred Werner isolated these two isomers, which showed conclusively that the complex is square planar rather than tetrahedral. The cis isomer is now known by the trade name cisplatinol or cisplatin, and it is used in treating certain forms of cancer. 

In seeking for an explanation of the fact that certain molecules which were saturated, according to old valency theory, still possessed the power to combine with other molecules, Alfred Werner,15 in 1S91, introduced his co-ordination theory which, altered and added to as it has been developed, he used to explain the existence of complex salts, and especially the large class of compounds known as the metal-ammines. It does not take into account the internal structure of the atoms linked together, but is concerned with the combining capacity... 

Chelate complexes of ethylenediamine provide many of the examples on which the theories of coordination chemistry have been founded. Co111 complexes of this ligand were studied by Alfred Werner and his students186 and the separation of or-CoCl(en)2(NH3)2+ into its optical enantiomers187 was a key factor in establishing octahedral stereochemistry. 

Metal complexes have characteristic shapes, depending on the metal ion s coordination number. Two-coordinate complexes, such as [Ag(NH3)2]+, are linear. Four-coordinate complexes are either tetrahedral or square planar for example, [Zn(NH3)4]2+ is tetrahedral, and [Ni(CN)4]2 is square planar. Nearly all six-coordinate complexes are octahedral. The more common coordination geometries are illustrated in Figure 20.12. Coordination geometries were first deduced by the Swiss chemist Alfred Werner, who was awarded the 1913 Nobel Prize in chemistry for his pioneering studies. 

Photochemistry as a science is quite young we only need to go back less than one century to find its early pioneer [1], The concept of coordination compound is also relatively young it was established in 1892, when Alfred Werner conceived his theory of metal complexes [2]. Since then, the terms coordination compound and metal complex have been used as synonyms, even if in the last 30 years, coordination chemistry has extended its scope to the binding of all kinds of substrates [3,4],... 

Tphe bright colors of the coordination complexes of transition metal elements, including the platinum group metals, were of great assistance to pioneer workers with these materials. Thus, chemical changes could be followed visually it was frequently very easy from their colors to demonstrate the existence of isomers upon which Alfred Werner was able to base his monumental theory of coordination. Such early studies were limited to a simple qualitative visual evaluation of the color. 

It was her thesis work with Alfred Werner34 that was to enter her in the annals of the history of chemistry. Among the compounds she made was cis-bis(ethylenediamine)dinitro-cobalt(III) bromide. This was the very first synthesis of a chiral octahedral cobalt complex, though at the time the significance of her synthesis was overlooked.31(a) Werner was so impressed with her work that, for her last year, he took her on as his personal assistant, the first women to be chosen for this prestigious post.35 More important for the impoverished Humphrey, she at last had some income in very expensive Switzerland. 

Fig. 2 How Alfred Werner assigned an octahedral structure to the two isomeric complexes of formula [Coln(NH3)4Cl2]Cl. Only the octahedral geometry is consistent with the formation of two isomers the green (1,4) tram isomer and the violet (1,2) cis isomer...

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