Werner coordination theory

These two compounds, originally called Peyrone s salt and Reiset s second chloride, respectively, have long been known and have played an important role in the historical development of coordination theory. Werner s suggestion that these compounds are cis and trans isomers represents the earliest proposal of a planar configuration for bivalent platinum. He correctly identified these compounds by using his classical concept of "trans elimination. ... 

G. B. Kauffman, Alfred Werner Founder of Coordination Theory, Springer, Berlin, 1966, 127 fp. G. B. Kauffman (ed.) Coordination Chemistry A Century of Progress, ACS Symposium Series 565, Washington DC, 1994, 464 pp. 

Werner s coordination theory, 1, 6 Whewellite structure, 6, 849 Wickmanite structure, 6, 849 Wilkinson s catalyst, 6, 239 Wilson s disease, 5, 721 copper, 6,648 removal, 6,769 copper complexes, 2,959 copper metabolism, 6,766 radiopharmaceutical agents, 6,968 Wolfram s red salt, 5,427 Wurzite... 

Noyes himself had been a student of Ostwald. Lewis had spent the academic year 190001 at the institutes of Ostwald and Nernst. Colloquium topics at MIT in the period from roughly 1905 to 1910 included both chemical and physical topics Alfred Werner s coordination theory of valence, tautomerism, and the absolute size of atoms. 

Isomerism in the Metal-ammines.—Werner claimed for the coordination theory that in certain cases isomerism should occur, that isomerism being brought about by different causes. lie divided isomerism in the ammines into five groups, namely, structure isomerism, ionisation isomerism, hydrate isomerism, polymerism, and stereoisomerism. 

Claus first postulate was vigorously attacked by Karl Weltzien (1813—1870),40 while Hugo Schiff (1834—1915)43 attacked not only Claus first postulate but also his second. All of Claus three postulates reappeared modified almost four decades later in Werner s coordination theory. Claus third postulate closely adumbrates Werner s concepts of the coordination number and of the transition series between metal ammines and metal salt hydrates. 

Whereas Kekule disposed of complex compounds by banishing them to the limbo of molecular compounds , other chemists developed highly elaborate theories to explain their constitution and properties. The most successful and widely accepted of such pre-Werner theories was the chain theory,47 advanced by Christian Wilhelm Blomstrand (1826-1897)4 and developed by Sophus Mads Jorgensen (1837—1914).46 49 50 Although Werner s ideas eventually triumphed, this did not invalidate Jorgensen s observations. On the contrary, his experiments have proven completely reliable and provided the experimental foundation not only for the Blomstrand—Jorgensen chain theory but also for Werner s coordination theory. 

The circumstances surrounding the creation of Werner s coordination theory provide us with a classic example of the flash of genius . One night in late 1892, Werner awoke at 2 a.m. with the... 

Table 1 shows a comparison of the formulas and predicted numbers of ions for the transition series [Co(NH3)6](N02)3. .. K3[Co(N02)6] according to the two theories, and Figure 1 shows the results of Werner s first published experimental work in support of his coordination theory, a study of conductances carried out in collaboration with his friend and former fellow student Arturo Miolati (1869—1956).63... 

In their first publication on this subject,59 Werner and Miolati showed that the molecular conductances (fx) of coordination compounds decreased as successive molecules of ammonia were replaced by acid residues (negative groups or anions). For cobalt(III) salts, they found that fi for luteo salts (hexaammines) > fi for purpureo salts (acidopentaammines) > /t for praseo salts (di-acidotetraammines). The conductance fell almost to zero for the triacidotriammine Co(N02)3-(NH3)3 and then rose again for tetracidodiammines, in which the complex behaved as an anion. By such measurements, Werner and Miolati determined the number of ions in complexes of cobalt(III), platinum(II) and platinum(IV). They not only found support for the coordination theory, but they also elucidated the process of dissociation of salts in aqueous solution and followed the progress of aquations. 

The resolution of optically active coordination compounds, a feat which shook chemistry to its innermost foundations ,72 gained for the coordination theory the widespread recognition for which Werner had been striving for so long. Nor was the theory s founder neglected, for two years later, largely in recognition of the most brilliant confirmation of [his] stereochemical views ,73 Werner was awarded the Nobel Prize in chemistry for 1913.74... 

Even so great an admirer of Werner as Paul Pfeiffer (1875-1951),93 Werner s former student and one-time chief of staff at the University of Zurich and the man who first applied Werner s theory to crystal structures (see Section 1.1.5.4), proposed modifications of the coordination theory. He applied what he called the principle of affinity adjustment of the valencies to overcome certain shortcomings of Werner s theory.94 He considered the ionizable radicals or atoms in the outer sphere to be combined with the complex radical as a whole and not attached definitely to the central atom or to any of its associated molecules. He also applied this idea to complex organic molecular compounds. However, Pfeiffer s modifications should not be interpreted as attacks on Werner s ideas. 

Werner apparently did not realize that the polynuclear complexes which he investigated so extensively95 constituted a transition between the usual mononuclear coordination compounds and the infinite structure of the crystal lattice. It remained for Paul Pfeiffer, Paul Niggli (1888—1953) and others to point out that crystal structures were in beautiful agreement with his coordination theory, as revealed by the then new experimental technique of X-ray diffraction.96... 

Since Dickinson s first determinations, crystal structures of many other complexes of various coordination numbers have been determined. All these investigations and others have provided a complete and direct confirmation of Werner s views to support his indirect configurational proofs obtained during the previous decades by preparation of isomers and resolution of optically active compounds (see Section 1.1.4), and today the terminology and concepts of coordination theory are routinely used in crystallography. 

Octahedral Six Coordinate In addition to the tris-bidentate complexes and the unidentate complexes discussed above, there are many other examples of chiral metal complexes that are based on octahedral geometry. For example, there are a number of reports of edge-sharing binuclear structures containing four bidentate chelates. The individual metal centers in these binuclear species can exist as either A or A enantiomers, and, therefore, the overall structure can be chiral AA and AA, or the achiral (meso) AA pair as illustrated in Figure 5.12a and b. Studies of complexes of this type were important in the proof of Werner s coordination theory. In these pioneering studies, Werner was able to prove by experiment the existence of the three isomers (AA, AA, and AA) of [Co2(p-NH2)( l-NC>2)(en)2]4 +. 23 For Cr(III) complexes, Werner showed that the / >.vo-AA- Cr2(p-OH)2(en)414 1 may be prepared by... 

Koord. Khim. ( Russ. J. Coord. Chem. ) 19(5), 331-408 (1993) (issue dedicated to 100 years of Werner s coordination theory). 

A recent review [440], published 100 years after Werner s coordination theory was first presented, was dedicated to the complex compounds obtained on the basis of polypyrazolyl-borates or scorpionates. Complexes of this kind, an example of which is presented by structure 234, have been obtained with practically all p, /-elements and they can be examined as N-containing analogoues (MN4 coordination unit) of p-diketonates 2 (M04 coordination unit) ... 

Metal complexes (complex compounds or coordination compounds) are one of the most important groups of chemical compounds and form the basis of coordination chemistry. Although complex compounds date back to the 18th century, coordination chemistry was considered a science only after the formulation of the coordination theory by the Swiss chemist A. Werner at the end of the 19th century [1], During the 20th century, thousands of metal complexes were obtained, characterized, and widely applied. Much has been written on heir synthesis, structure, and properties [2-13],... 

Fig. 2.18 Alfred Werner (1866-1919) is usually described as the founder of coordination chemistry. Werner did his Ph.D. in 1889 with Professor Arthur Hantzsch and, after spending one semester with Marcellin Berthelot at the College de France at Paris, returned to the ETH at Zurich to finish his Habilitation in 1892. One year later, he became Associate Professor at the University of Zurich and was promoted as Professor of Chemistry in 1895. Remarkably, despite the widespread attention for his groundbreaking coordination theory, he was not permitted to give the basic lecture in inorganic chemistry before 1902. Werner attracted students from all over the world, supervised 230 Ph.D. theses and was the first Swiss to receive the Nobel Prize for Chemistry in 1913. In his famous book Valence and the Structure of Atoms and Molecules , published in 1923, Gilbert N. Lewis wrote ...in attempting to clarify the fundamental ideas of valence, there is no work to which I feel so much personal indebtedness as to this of Werner s (photo from Helv. Chim. Acta 75, 21-61 (1992) reproduced with permission of Dr. Kisaktirek, Editor of Helvetica Chimica Acta)...

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