Ligand substitution reactions compounds

Scheme 6. Turnstile mechanism for the ligand substitution reactions of oxo-rhenium(V) compounds.

C. Axial Ligand Substitution Reactions of Dinuclear Pt(3.0+)2 Compounds... 

A solution of the isolated platinum blue compound usually contains several chemical species described in the previous section. Such complicated behaviors had long been unexplored, but were gradually unveiled as a result of the detailed equilibrium and kinetic studies in recent years. The basic reactions can be classified into four categories (l)HH-HT isomerization (2) redox disproportionation reactions (3) ligand substitution reactions, especially at the axial coordination sites of both Pt(3.0+)2 and Pt(2.5+)4 and (4) redox reactions with coexisting solvents and atmosphere, such as water and 02. In this chapter, reactions 1-4 are summarized. 

A Co(IH) complex is inert in ligand-substitution reactions, and its uniform structure is thus maintained even in an aqueous solution. The reaction mechanism of a Co(III) complex in solution is well known, so that a pendant-type polymer-Co(IU) complex, e.g. 17,19, is one of the most suitable compounds for a quantitative study of the effects of a polymer ligand on the reactivity of a metal complex. The reactivities of the polymer-Co(III) complexes are discussed here kinetically and compared with those of the monomeric Co(III) complexes in the following reactions electron-transfer reactions between the polymer complexes and Fe(II) [Eqs. (5) and (6)], and the ligand-substitution reaction of the polymer-Co(III) complex with hydroxy ions or water [Eqs. (7) and (8)J. One of the electron-transfer reactions proceeds via... 

Photocalorimetry offers a convenient alternative to other methods of AH determination and, in some instances, may be the only practical method. The ligand substitution reactions of robust Werner-type complexes are a case in point. Conventional thermochemical measurements are complicated by the slowness of the substitution process and/or by competing reactions. Some of these same complexes, however, undergo clean photosubstitutions with high quantum yields and thus are excellent candidates for photocalorimetry. Examples include [Cr(NH3)6]3+, [Cr(CN)6]3-and [Co(CN)6]3-.192 Photocalorimetric measurements of AH have also been obtained for isomerization and redox reactions of coordination compounds.193194... 

Support-bound transition metal complexes have mainly been prepared as insoluble catalysts. Table 4.1 lists representative examples of such polymer-bound complexes. Polystyrene-bound molybdenum carbonyl complexes have been prepared for the study of ligand substitution reactions and oxidative eliminations [51], Moreover, well-defined molybdenum, rhodium, and iridium phosphine complexes have been prepared on copolymers of PEG and silica [52]. Several reviews have covered the preparation and application of support-bound reagents, including transition metal complexes [53-59]. Examples of the preparation and uses of organomercury and organo-zinc compounds are discussed in Section 4.1. 

In contrast, those cluster compounds with an 18-electron environment at the central heterometal do not undergo nucleophilic addition reactions. Ligand substitution reactions at both the central heterometal and the peripheral gold atoms are observed to occur for both 16- and 18-electron cluster compounds, as in the reactions shown below ... 

Similar ligand substitution reactions, in which substitution occurs at the transition metal center, have been reported for smaller hetero-nuclear cluster compounds,... 

Finally, while the new synthetic methods for technetium compounds in the oxidation states I, II and V will undoubtedly play an important role in the development of improved radioscintigraphic agents, there remains a need to understand the chemical mechanisms involved in these syntheses, particularly with regard to ligand substitution reactions and atom transfer redox processes. Mechanistic studies to complement the increasing body of structural knowledge is essential to the further development of technetium radiopharmaceuticals. 

Ligand substitution is one of the most characteristic reactions of coordination compounds. If in the early stages of the development of coordination chemistry a ligand substitution reaction served as a synthetic method, then later on, especially after Werner, such reactions were widely employed both to solve structural problems (viz., geometric isomerism), and to elucidate the nature of a trans effect. 

Lanthanides, 9, 361-380 Lead compounds, 6, 247-250 7, 245-256 Ligand substitution reactions in metal tt-complexes, 10, 347-409 Lithium alkyls, 6, 202 8, 168-170... 

Louie, J., Hartwig, J. F. Transmetalation, Involving Organotin Aryl, Thiolate, and Amide Compounds. An Unusual Type of Dissociative Ligand Substitution Reaction. J. Am. Chem. Soc. 1995,117,11598-11599. 

Reaction chains are sequences of transformations in which the product of one reaction serves as starting material for the next. A cycle is a closed chain of ligand substitution reactions that connects compounds in a circular sequence In this use of the word compound, enantiomers are not distinguished. In a reaction cycle, the number of reactions equals the number of compounds. The directions of the arrows for the reactions of a cycle are incidental to the properties of the cycle. In the generalized three-reaction, three-compound cycle formulated, any of the arrows could point in either direction. 

Once Cd(CF3)2DME had been isolated, the first experiments with the reagent were devoted to comparing the reactivity of the new compound with that of Hg(CF3)2 in ligand substitution reactions of main group metalloids. The results shown in Eqs. (5)—(8) clearly indicated that at least with Ge and Sn halides, the cadmium-based trifluoromethylating reagent... 

This reaction results in the quantitative formation of insoluble Zn(DBM)2(TMEDA) and a soluble organotin oligomer. It is clear that in this reaction Sn[(CH2)3NMe2]2 is liberated by a ligand-substitution reaction and undergoes the fast oligomerization reaction that is common for simple dialkyl- and diaryl-tin(H) compounds (77). 

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