Water adducts, metal

Metal-Water Adduct Frequencies and Frequency Shifts Av for the Bending Mode in the Metal-Water Adducts (cm )... 

Our studies have shown that almost all metal atoms will form an adduct with water and in many instances undergo further reaction. Theory and experiment (1 -7 ) support the concept of water acting as a Lewis base which donates electron density to the metal. Theory has also shown for Be and Mg that donation occurs extensively from the 3ai (a lone pair) orbital of water to the metal. This is of interest since this orbital is largely responsible for the nonlinearity of the water molecule. It is known, for instance, that ionization from this orbital causes water to become linear and results in a decrease in its bending frequency by approximately 700 cm . This is consistent with our finding that only the V2 bending mode of water decreases measurably upon adduct formation. The observed Av2 changes for metal-water adducts are compared and discussed below. 

Bending Mode in Main Group Metal -Water Adducts. ... 

It is also very Interesting to note the large differences in Av 2 for the metal atom and diatomic species. Chromium and iron atoms differ by a factor of two from the diatom but in opposite directions. Finally, Al, Sc, Ti and V reacted rather than form a stable metal-water adduct while Ni did not form an adduct or react. 

The structure of the metal-water adduct has been determined experimentally for Li(, 7) and theoretically for Li, Na( ), Be, Mg(3,4), Ca(5), and Al(2). In all cases water is acting as a Lewis base and donating electron density to the metal through the oxygen. For all metals but Be the minimum energy geometry is planar. For Be, the Be-0 bond is calculated to be symmetrical... 

In reality, the second possibility occurred (57), and the same was true for the adducts containing other olefins. Finally, we verified the presence of hydroxyl in structure (IV) through reaction with phenyl isocyanate. Thus, the convincing experiments of Hoffmann, Middleton, and R. Adams were confirmed by our decisive evidence, so that 7T-structures were condemned to fade from the scene for these compounds. However, to emphasize the behavioristic similarity with the 77-complcxes, I suggested the term quasicomplex for the compounds which are formed from metallic salts and olefins or acetylenes through addition to the 7T-bond. A number of such quasi-complex compounds were obtained and studied by us. In particular, we showed that butadiene or its homologs, contrary to the earlier opinion of Sand, also formed the quasi-complex adducts in water, e.g.,... 

This salt is a dark-red solid which forms stable 1 1 adducts with water, methanol, and diethyl ether. The solvent in these complexes is tightly held and is only removed by heating in a vacuum. These molecules (H2O, CH3OH) are utilized in a number of metal carbonyl catalyzed reactions, either as a source of hydrogen or to furnish hydroxide or methoxide radicals or ions. 

The in situ generation of the carbon dioxide adduct of an indole provides sufficient protection and activation of an indole for metalation at C-2 with r-butyl-lithium. The lithium reagent can be quenched with an electrophile, and quenching of the reaction with water releases the carbon dioxide. ... 

A corrosion inhibitor with excellent film-forming and film-persistency characteristics is produced by first reacting Cig unsaturated fatty acids with maleic anhydride or fumaiic acid to produce the fatty acid Diels-Alder adduct or the fatty acid-ene reaction product [31]. This reaction product is further reacted in a condensation or hydrolyzation reaction with a polyalcohol to form an acid-anhydride ester corrosion inhibitor. The ester may be reacted with amines, metal hydroxides, metal oxides, ammonia, and combinations thereof to neutralize the ester. Surfactants may be added to tailor the inhibitor formulation to meet the specific needs of the user, that is, the corrosion inhibitor may be formulated to produce an oil-soluble, highly water-dispersible corrosion inhibitor or an oil-dispersible, water-soluble corrosion inhibitor. Suitable carrier solvents may be used as needed to disperse the corrosion inhibitor formulation. 

The corrosion of metal surfaces and the precipitation of a metal sulfide by an aqueous acid solution can be prevented by an aldol-amine adduct. Aldol (from acetaldehyde) CH3CH(OH)CH2CHO has been utilized as a H2S scavenger that prevents the precipitation of metal sulfides from aqueous acid solutions. However, when the aldol or an aqueous solution of the aldol is stored, the solution separates quickly into two layers, with all of the aldol concentrated in the bottom layer. The bottom layer is not redispersible in the top layer or in water or acid. In addition, the aldol in the bottom layer has very little activity as a sulfide scavenger. Thus the use of aldol as a H2S scavenger in aqueous acid solutions can result in unsatisfactory results [245,247]. However, the aldol can be reacted with an amine, such as monoethanoleamine (=aminoethanol), to form an aldol-amine adduct to overcome these difficulties. The amine utilized to prepare the aldol-amine adduct must be a primary amine. The aldol-amine adduct preferentially reacts with sulfide ions when they are dissolved in the... 

With an electrophilic transition metal complex, it is believed that the hydration of an alkyne occurs through a trans-addition of water to an 72-alkyne metal complex (Scheme 15, path A),380 although the m-pathway via hydroxymetallation has also been proposed (path B).381,382 However, distinguishing between the two pathways is difficult due to the rapid keto-enol tautomerization that renders isolation of the initial water adduct challenging. 

Judging from these findings, the mechanism of Lewis acid catalysis in water (for example, aldol reactions of aldehydes with silyl enol ethers) can be assumed to be as follows. When metal compounds are added to water, the metals dissodate and hydration occurs immediatdy. At this stage, the intramolecular and intermolecular exchange reactions of water molecules frequently occur. If an aldehyde exists in the system, there is a chance that it will coordinate to the metal cations instead of the water molecules and the aldehyde is then activated. A silyl enol ether attacks this adivated aldehyde to produce the aldol adduct. According to this mechanism, it is expected that many Lewis acid-catalyzed reactions should be successful in aqueous solutions. Although the precise activity as Lewis acids in aqueous media cannot be predicted quantitatively... 

FIGURE 1.2. Formation of nanoparticles of metal oxide by reverse micelle method. A solution of inverse micelles is first formed by adding a long-chain alkylamine to a toluene solution. A small amount of water is trapped in the reverse micelle core. Mixing the reverse micelle solution with an aluminum alkoxy amine adduct results in hydrolysis of the aluminum alkoxide adduct and formation of nano-sized particles of aluminum oxyhydroxide after drying. These particles are shown in the SEM picture above. 

All metal ions in water are hydrated, and at higher pH most of them also hydrolyze. It can be difficult to distinguish between the hydrolyzed and the complexed species, as well as their self-adducts. For such systems, plots of against [A ] at various pH and total concentrations of [HA] show three types of curves (a) for the simple chelate MA , (b) for the self-adduct MA (HA), and... 

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