Ionization isomerism

Isomerization Ionization by loss of an electron - this usually results in reaction of the cationic ... 

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... 

Bond dissociation Reaction with other species Isomerization Ionization... 

Acid-catalyzed isomerization reactions of alkanes as well as alkylation and condensation reactions are initiated by protolytic ionization. Available evidence indicates nonlinear but not necessarily triangular... 

Indazoles have been subjected to certain theoretical calculations. Kamiya (70BCJ3344) has used the semiempirical Pariser-Parr-Pople method with configuration interaction for calculation of the electronic spectrum, ionization energy, tt-electron distribution and total 7T-energy of indazole (36) and isoindazole (37). The tt-densities and bond orders are collected in Figure 5 the molecular diagrams for the lowest (77,77 ) singlet and (77,77 ) triplet states have also been calculated they show that the isomerization (36) -> (37) is easier in the excited state. 

Like the un-ionized hydroxyl group, an alkoxy group is a weak nucleophile. Nevertheless, it can operate as a neighboring nucleophile. For example, solvolysis of the isomeric p-bromobenzenesulfonate esters 6 and 7 leads to identical prxKluct nuxtures, suggesting the involvement of a common intermediate. This can be explained by involvement of the cyclic oxonium icai which would result from intramolecular participation. ... 

This type of isomerism occurs when isomers produce different ions in solution, and is possible in compounds which consists of a complex ion with a counter ion which is itself a potential ligand. The pairs [Co(NH3)5(N03)]S04, [Co(NH3)5(S04)]N03 and [PtCl2(NH3)4]Br2, [PtBr2(NH3)4]Cl2, and the series [CoCl(en)2-(N02)]SCN, [CoCl(en)2(SCN)]N02, [Co(en)2-(N02)(SCN)]C1 are examples of ionization isomers. 

Both CSs and CSs were also successfully generated by the fragmentation of ionized 4,5-dioxo-2-thioxo-l,3-dithione (65) and 2-thioxo-l,3-dithiole (66) (90JA3750). Tire three sulfur atoms in the anion and cation radicals were chemically equivalent, suggesting that they take the D h (or C2u) form (67 or 68). On the other hand, under similar conditions, 3-thioxo-1,2-dithiole (69) yielded two isomeric cation radicals the (or 2 ) form and the carbon disulfide 5-sulfide form (70). Ab initio calculations on three electronic states of CS3 at the 6-31G -l-ZPVE level indicated that the C21, form (68) was more stable than the carbon disulfide 5-sulfide form (70) in the neutral (both singlet and triplet states) and the anion radical states, but 68 was less stable than 70 in the radical cation state. 

Intramolecular cycloadditions of substrates with a cleavable tether have also been realized. Thus esters (37a-37d) provided the structurally interesting tricyclic lactones (38-43). It is interesting to note that the cyclododecenyl system (w = 7) proceeded at room temperature whereas all others required refluxing dioxane. In each case, the stereoselectivity with respect to the tether was excellent. As expected, the cyclohexenyl (n=l) and cycloheptenyl (n = 2) gave the syn adducts (38) and (39) almost exclusively. On the other hand, the cyclooctenyl (n = 3) and cyclododecenyl (n = 7) systems favored the anti adducts (41) and (42) instead. The formation of the endocyclic isomer (39, n=l) in the cyclohexenyl case can be explained by the isomerization of the initial adduct (44), which can not cyclize due to ring-strain, to the other 7t-allyl-Pd intermediate (45) which then ring-closes to (39) (Scheme 2.13) [20]. While the yields may not be spectacular, it is still remarkable that these reactions proceeded as well as they did since the substrates do contain another allylic ester moiety which is known to undergo ionization in the presence of the same palladium catalyst. 

Figure 16.18 summarizes the types of isomerism found in coordination complexes. The two major classes of isomers are structural isomers, in which the atoms are connected to different partners, and stereoisomers, in which the atoms have the same partners but are arranged differently in space. Structural isomers of coordination compounds are subdivided into ionization, hydrate, linkage, and coordination isomers. 

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