Pfeiffer, Paul

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... 

Pfeiffer, Paul (1928). Alfred Werner. Journal of Chemical Education 5 1,090-1,098 reprinted in Great Chemists, ed. Eduard Farber. New York Interscience Publishers (1961), pp. 1,233-1,243. 

Pfeiffer, Paul Lokalisaiion und spezifische Wirkung der Nebenvalenz-... 

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. 

Paul Pfeiffer discovered a very interesting stereochemical phenomenon, which now bears his name — the Pfeiffer effect this has received a good deal of attention.30 When an optically active substance which is stable in solution is added to a solution of a labile chiral substance, the optical rotation of the solution changes, reaching a new level in some hours. Several theories have been advanced to explain the phenomenon, the most satisfactory based on the supposition that the optically active ion or molecule forms an association with one isomer of the racemic pair of the labile substance and thus shifts the dextro—levo equilibrium. In general it is not possible to use this as a means of resolution, for when the added optically active substance is removed from the labile material, the latter immediately racemizes. 

Paul Rassiner, Das Drama der Juden Europas, H. Pfeiffer, Hannover 1965... 

The systematic study of acid-base properties of coordination compounds was initiated in 1906 by Werner s former student and co-worker, Paul Pfeiffer (55), who found that hydroxoammines of chromium could react with acids to form oxonium-like aquo salts which could in turn react with bases to reform the original compound ... 

J ekul s theory of constant or fixed valency undoubtedly helped Werner and Hantzsch develop their theories of the stereoisomeric forms of oximes and diazo compounds. However, Werner soon felt that Kekul s ideas were too rigid and, being convinced that sufficient facts were now at hand to justify a new theory, outlined one for variable valency. He then spent the rest of his life producing experimental proofs. This is not the whole story, but it can serve to introduce Alfred Werner. Two of his pupils may be quoted Paul Pfeiffer (29) Contribution... 

Werner received the Nobel prize in 1913, and about this time began to suffer from arteriosclerosis, but he did not become seriously ill until 1915. Then his assistants, Paul Karrer and Paul Pfeiffer, took over for him until his death on November 15, 1919. Karrer remained at the University of Zurich where his work with the vitamins has brought fame to him and... 

None of Werner s colored compounds were good dyes, but the significant point is that his student, Paul Pfeiffer 51 y 52) y adopted the coordinate theory of Werner and applied it with success to an expanding group of new and old colored compounds. The applications of the coordinate theory of metal complexes may be separated into the following divisions ... 

Pentan-2-amme, 4.4 -(ethyleiiediimino)bis-complexcs structure, 25 Peptides metal complexes deuterium exchange, 426 hydrolysis, 428, 440 Peyrone s reaction, 17 Peyrone s salt configuration, 17 history, 3 Pfeifier, Paul, 1.5 Pfeiffer effect, 26... 

Many pigments and dyes of historical interest exhibit the capability of forming Werner-type coordination complexes. The relationships between the structures and color characteristics of these colorants are reviewed in this paper, with particular attention to the work of Paul Pfeiffer, a student and long-time assistant of Alfred Werner s who did extensive work in the characterization and application of Werner s coordination theory to alizarin-related dyes. 

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