Complexation reactions of metals

In the following chapters the complex reaction of metals with macromolecules is discussed separately for each metal ion. To conclude this series an attempt will be made to correlate metal-polynucleotide interactions with biochemical pathways. 

Complex reaction of metal compounds with oxygen and subsequent formation of an H02- radical. 

The complexation of neutral molecules by ligands covalently bound to polymer supports requires the study of a set of parameters different from those involving the complexation reactions of metal ions. While the latter emphasizes ion exchange mechanisms, the former relies on reactions such as acid/base interactions for selectivity. The role of the polymer support in molecular complexation reactions has been the focus of this part of our research studies are being undertaken to determine whether the polymer acts only as an inert matrix on which to bond appropriate ligands, or whether it can also influence the ligand-molecule interaction. 

Figure 4. Steps proposed for polymerized complex reaction of metal ions, citric acid and ethylene glycol...

Bitumen Ionomers. Moisture-resistant asphalts (qv) have been prepared by reaction of metal oxides with acid-functionalized bitumens (75). Maleic anhydride or sulfur trioxide/trimethylamine complexes have been used successfully for introduction of acid groups into asphaltic bitumens. 

Silica Polymei Metal Ion Interactions in Solution. The reaction of metal ions with polymeric sihcate species in solution may be viewed as an ion-exchange process. Consequently, it might be expected that sihcate species acting as ligands would exhibit a range of reactivities toward cations in solution (59). Sihca gel forms complexes with multivalent metal ions in a manner that indicates a correlation between the ligand properties of the surface Si-OH groups and metal ion hydrolysis (60,61). For Cu +, Fe +, Cd +, and Pb +,... 

The increased acidity of the larger polymers most likely leads to this reduction in metal ion activity through easier development of active bonding sites in siUcate polymers. Thus, it could be expected that interaction constants between metal ions and polymer sdanol sites vary as a function of time and the sihcate polymer size. The interaction of cations with a siUcate anion leads to a reduction in pH. This produces larger siUcate anions, which in turn increases the complexation of metal ions. Therefore, the metal ion distribution in an amorphous metal sihcate particle is expected to be nonhomogeneous. It is not known whether this occurs, but it is clear that metal ions and siUcates react in a complex process that is comparable to metal ion hydrolysis. The products of the reactions of soluble siUcates with metal salts in concentrated solutions at ambient temperature are considered to be complex mixtures of metal ions and/or metal hydroxides, coagulated coUoidal size siUca species, and siUca gels. 

Reaction of metal hydride complexes with N-nitrosoamides, e.g. Af-methyl-7V-nitrosourea ... 

H. Taube (Stanford) mechanisms of electron transfer reactions of metal complexes. 

Another type of tautomerization was observed in the complexation reaction of 5-oxo tautomers of pyrazolone with metal chlorides 362 (89ZNK 2966). 

In spite of their intrinsic synthetic potential, addition reactions of metal enolates of non-stabilized esters, amides, and ketones to epoxides are not widely used in the synthesis of complex molecules. Following the seminal work of Danishefsky [64], who introduced the use of Et2AlCl as an efficient catalyst for the reaction, Taylor obtained valuable spiro lactones through the addition reaction of the lithium eno-late of tert-butyl acetate to spiro-epoxides, upon treatment of the corresponding y-... 

Volume 6 Volume 7 Reactions of Non-metallic Inorganic Compounds Reactions of Metallic Salts and Complexes, and Organometallic Compounds Section 4. ORGANIC REACTIONS (6 volumes)... 

Reactions of Metallic Salts and Complexes, and Organometallic Compounds... 

Mechanisms of substitution reactions of metal complexes. F. Basolo and R. G. Pearson, Adv. Inorg. Chem. Radiochem., 1961, 3, 1-89 (132). 

The mechanistic assignment of terms in empirical rate laws for complexation and redox reactions of metal ions in aqueous solution acid dependences in perchlorate media. G. Davies, Coord. Chem. 

Application of molecular orbital theory to electron transfer reactions of metal complexes in solution. J. K. Burdett, Comments Inorg. Chem., 1981,1, 85-103 (7). 

Reagent and catalyst induced substitution reactions of metal carbonyl complexes. M. O. Albers and N. J. Coville, Coord. Chem. Rev., 1984, 53, 227-259 (153). 

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

One other point to note in regard to this study (141) is that any evidence of oxidative addition, particularly with the chloro-olefins, was absent. The similarity of the spectra, coupled with the nonobservation of any bands in the visible region, as well as the observation of vc-c in the region commonly associated with 7r-complexation of an olefin (141, 142), all argue in favor of normal ir-coordination, rather than oxidative insertion of the metal atom into, for example, a C-Cl bond. Oxidative, addition reactions of metal atoms will be discussed subsequently. 

Dihydro-l,2-azaborolyl sandwich complexes, available by metal-vapor synthesis ( 6.5.3.3), can be prepared in a greater variety by reaction of metal halides with azaborolyl anions, e.g. " ° ... 

Reactions of metal halides with polysulfide dianions are useful methods for the synthesis of polysulfido complexes of main group elements and transition metals. In most of these reactions, similarly to other methods, the chain lengths and coordination types of the polysulfide ligands depend on the other ligands coordinated to the metal, on the ratio between the metal and sulfur, on the reaction temperature, and other parameters. 

Scheme 30 Synthesis of metal polysulfido complexes by the reaction of metals with Sg...

As the reaction of metal-carboxamido complexes (e.g., [Pt(PPh3)2-(CNCH3)(C0NHCH3)] ) with proton donors proceed in the same way - [Pt(PPh3)2(CNCH3)(CO)] " 147) the product of this reaction is not unexpected. One notes that relatively severe conditions are employed in this reaction 11). 

A60. J. P. Candlin, K. A. Taylor, and D. T. Thompson, "Reactions of Transition-Metal Complexes. Elsevier, Amsterdam, 1968. A review of types of reactions of metal complexes (e.g., substitution, combination, redox) reactions with various reagents (e.g., hydrocarbons, halides, carbon monoxide, and isonitrile) and preparation of new stabilised organic systems (e.g., metallocenes, carbenes). Intended for research workers, consequently written at a fairly high level, with emphasis on organometallics. A61. H. J. Keller, NMR-Untersuchungen an Komplexverbindungen. Springer, Berlin, 1970. Expansion of review article 37.1. 

J. Lewis and R. S. Nyholm Structure and reactions of metal complexes of chelate olefin ligands, pp. 61-99 (37). 

Dirheniumheptoxide 2154 is converted by TCS 14, in the presence of 2,2 -dipyri-dine, into the dipyridine complex 2160 [77]. Free ReCls, NbCls, and WCI5 react with HMDSO 7 and 2,2 -bipyridine to form bipyridine oxochloride complexes 2161 and TCS 14, with reversal of the hitherto described reactions of metal oxides with TCS 14. The analogous Mo complex 2162 undergoes silylahon-amination by N-trimethylsilyl-tert-butylamine 2163 to give the bis-imine complex 2164 and HMDSO 7 [77] (Scheme 13.22). 

As regards intimate mechanism, electron transfer reactions of metal complexes are of two basic types. These have become known as outer-sphere and inner-sphere (see Chapter 4, Volume 2). In principle, an outer-sphere process occurs with substitution-inert reactants whose coordination shells remain intact in... 

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