Isomerism, coordination

Alfred Werner s research on geometrically isomeric coordination compounds. G. B. Kaufmann, Coord. Chem. Rev., 1975, 15,1-92 (564). 

Figure 2. Proposed mechanisms for the alkyne to vinylidene isomerization coordinated to a transition metal fragment...

To obtain a first impression of the nonadiabatic wave-packet dynamics of the three-mode two-state model. Fig. 34 shows the quantum-mechanical probability density P (cp, f) = ( (f) / ) (p)(cp ( / (f)) of the system, plotted as a function of time t and the isomerization coordinate cp. To clearly show the... 

The tetramethyl derivatives (5 R=CH3) are chosen as model system to lower computational costs and, above all, to lay bare the electronic effects, which might be obscured by the steric requirement of the bulky tert. butyl groups (28, ). To further facilitate the calculations, a single isomerization coordinate a, along which the tetrahedron is flattened to a rectangle, has been chosen ... 

Fig. 1. Energy scheme of the 1+1 REMPI. Approximate potential curves across the isomerization coordinate 0 for the ground state So as well as the intermediate Si resonance are depicted.

Hydrate Isomerism, Coordination Isomerism, and Polymerization Isomerism... 

Ionization isomerism Hydration isomerism Coordination isomerism Linkage isomerism Polymerization isomerism... 

In fact, Werner played such a central and almost monopolistic role in coordination chemistry that his name is virtually synonymous with the field. Even today, almost 75 years after his death in 1919, coordination compounds, particularly metal-ammines, are still colloquially called Werner complexes. The coordination theory not only provided a logical explanation for known "molecular compounds, but also predicted series of unknown compounds, whose eventual discovery lent further weight to Werner s controversial ideas. He showed how ammonia could be replaced by water or other groups, and he demonstrated the existence of transition series between ammines, double salts, and hydrates. Werner recognized and named many types of inorganic isomerism such as coordination isomerism, polymerization isomerism, ionization isomerism, hydrate isomerism, salt isomerism, coordination position isomerism, and valence isomerism. He also postulated explanations for polynuclear complexes, hydrated metal ions, hydrolysis, and acids and bases. His view of the two types of chemical... 

Kauffinan, G. B. "Alfred Werner s Research on Geometrically Isomeric Coordination Compounds, Coord Chem. Rev. 1975.15,1. 

In summary, isomeric coordination networks are obtained depending on the preparation and crystallization conditions. The reader is directed to the review by B. Moulton and M. J. Zaworotko for a thorough discussion on the relationship between supramolecular isomerism and network topology... 

Figure 3.28 A model cyanine dye system (a) A 6 electron in 5 orbital model cyanine system showing two formal VB structures, (b) the formal cis-trans isomerization coordinate (see next figure) (c) the branching-space vectors, which correspond to symmetric and antisymmetric skeletal deformation of the sigma frame (the symmetric motion connects the two VB structures shown in part (a).)...

Coordination compounds can exhibit constitutional isomerism (coordination and linkage) and stereoisomerism (geometric and optical). 

---