Hydroxy—metal complexation reaction

In the triple layer model one of the o-plane metal surface complexes is represented as bidentate, Eq. (6.9), while one of the P-plane metal surface complexes is represented as a hydroxy-metal surface species, Eq. (6.30). Davis and Leckie (1978) considered the hydroxy-metal complexation reaction to be more consistent with their experimental data. Often, an additional metal surface complex containing the background electrolyte anion is postulated to form in the P-plane ... 

Pinacolone, o-(diphenylphosphino)benzoyl-coordination chemistry, 2, 401 Ping-pong reactions copper(II) complexes, 5, 717 Piperidine, /V-hydroxy-metal complexes, 2, 797 P a values azole ligands, 2, 77 Plant roots amino acids, 2, 962 carboxylic adds, 2,962 Plants... 

Mass action equations. The first step in any calculation is to collate the mass action expressions that define the formation of the species. The way in which the formation constants can be used can be illustrated by considering a metal such as aluminium in an aqueous medium. Aluminium ions can undergo a number of hyrolysis reactions in water to form several hydroxy-metal complexes. The reactions can be written as the overall hydrolysis reactions and their associated equilibrium formation constants are shown below. 

This term is, unfortunately, used to describe several quite different chemical reactions. Hydrolysis as described here should not be confused with the reactions of metal cations with water to form hydroxy-metal complexes. 

Several metal carbonyl dusters (e.g. [Ru3(CO)i2] and [Ir4(CO),2]) have been investigated in solution as possible catalysts for the water gas shift reaction. [120] A plausible common mechanism has been proposed Nudeophilic attack by H2O or OH on an electrophilic metal center of the duster to form an unstable carbo-hydroxy metal complex, which is then decarboxylated to give a metal hydride from which H2 is eliminated. Hiis reaction is one of the relatively few for which there is good evidence for catalysis by dusters themselves, rather than fragments or metal aggregates formed from them. 

The concentration of aluminum in serum can be determined by adding 2-hydroxy-1-naphthaldehyde p-methoxybenzoyl-hydrazone and measuring the initial rate of the resulting complexation reaction under pseudo-first-order conditions.The rate of reaction is monitored by the fluorescence of the metal-ligand complex. Initial rates, with units of emission intensity per second, were measured for a set of standard solutions, yielding the following results... 

The discussion of the activation of bonds containing a group 15 element is continued in chapter five. D.K. Wicht and D.S. Glueck discuss the addition of phosphines, R2P-H, phosphites, (R0)2P(=0)H, and phosphine oxides R2P(=0)H to unsaturated substrates. Although the addition of P-H bonds can be sometimes achieved directly, the transition metal-catalyzed reaction is usually faster and may proceed with a different stereochemistry. As in hydrosilylations, palladium and platinum complexes are frequently employed as catalyst precursors for P-H additions to unsaturated hydrocarbons, but (chiral) lanthanide complexes were used with great success for the (enantioselective) addition to heteropolar double bond systems, such as aldehydes and imines whereby pharmaceutically valuable a-hydroxy or a-amino phosphonates were obtained efficiently. 

The reactions are those of functionalized 1-alkynes, the first of which were described for alkynes bearing substituted hydroxymethyl groups, such as substituted propargyl alcohols, HC=CCRR (OH), and often proceed further to form metal allenylidene complexes, by spontaneous dehydration of a (usually unobserved) hydroxy-vinylidene complex (Equation 1.22) ... 

The metal ion-water exchange process must be important in areas other than those of simple metal complex formation. For example, the discharge of nickel ion at a mercury cathode is probably controlled, not by diffusion, but by rearrangement of the water coordination shell. The estimated rates and heat of activation for this agree with the idea that this, in turn, is related to the water exchange process (66). Then too, the dimerization rate of metal hydroxy species may be controlled by water exchange. The reaction... 

In 1977, an article from the authors laboratories [9] reported an TiCV mediated coupling reaction of 1-alkoxy-l-siloxy-cyclopropane with aldehydes (Scheme 1), in which the intermediate formation of a titanium homoenolate (path b) was postulated instead of a then-more-likely Friedel-Crafts-like mechanism (path a). This finding some years later led to the isolation of the first stable metal homoenolate [10] that exhibits considerable nucleophilic reactivity toward (external) electrophiles. Although the metal-carbon bond in this titanium complex is essentially covalent, such titanium species underwent ready nucleophilic addition onto carbonyl compounds to give 4-hydroxy esters in good yield. Since then a number of characterizable metal homoenolates have been prepared from siloxycyclopropanes [11], The repertoire of metal homoenolate reactions now covers most of the standard reaction types ranging from simple... 

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... 

Transition metal complexes have been widely investigated as catalysts for the synthesis of alkoxysilanes via alcoholysis of hydrosilanes. The system provides a convenient method for the protection of hydroxy groups in organic synthesis and the synthesis of silyl ethers. The general reaction is shown in Eq. (59). 

Oxidation of Tetramethylethylene. Tetramethylethylene, TME, was an excellent model olefin since it was rapidly and selectively oxidized in the presence of many transition metal complexes (12). Oxidation of TME in the presence of the group VIII metal complexes [MCI(CO)-(Ph3P)2] (M = Rh, Ir) at 50°C gave two major products 2,3-dimethyl-2,3-epoxybutane, I, and 2,3-dimethyl-3-hydroxy-l-butene, II (Reaction 5). Reaction mixtures were homogeneous with no observable deposits of insoluble materials. Little oxidation occurred under these conditions in the absence of the metal complexes, but low yields of I and II were obtained in the presence of a radical initiator (Table I). Reactions were severely inhibited by hydroquinone. The ruthenium (II) complex, [RuCl2(Ph3P)3]2, also promoted efficient oxidation of TME yielding I... 

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