Of coordinated amine

The XPS results for cobalt at pH 4, particularly the Co 2p splitting (15 eV) and the absence of shake-up satellite structure, are indicative of cobalt(III). However, the N(amine)/Co atomic ratio of 2.7 indicates that some ammonia ligands have been displaced. Since it is known (22) that hydrolysis rates for cobalt(III) complexes are very slow, the presence of cobalt with a low number of coordinated amines, suggests that hydrolysis is induced via an interaction with the birnessite surface. The cobalt to manganese ratios for bulk and surface measurements are equivalent within experimental error, a result which is consistent with a reaction process occurring primarily at the surface. It is... 

Oxidative dehydrogenation reactions of alcohols and amines are widespread in enzymatic biochemistry, and are of potential importance with regard to the operation of fuel cells based on simple alcohols such as methanol. The nature of products, and their rates of formation, may vary depending on the reaction conditions, and a role of metal ions has been recognized. The oxidation of amines may lead to a variety of products (nitriles, nitro species, etc.) although dehydrogenated diimine products are obtained quantitatively when the oxidation of the amine occurs via coordination to metal centers. A review is available on the mechanisms of oxidative dehydrogenations of coordinated amines and alcohols (93). 

The cobalt(III)-promoted synthesis of /3-carboxyaspartic acid has also been reported464 by the intramolecular addition of coordinated aminate ion to the alkenic centre in the (3,3-bis(ethoxycar-bonyl)-2-propenoato)pentaamminecobalt(III) ion [(H3N)5CoOOCCH= C(C02Et)2]2+. In aqueous solution, an intramolecular addition of the cis-aminate ion at the alkenic centre gives the N,0-chelated diester of /3-carboxyaspartic acid (Scheme 37). 

The formation of alkoxo intermediates may be occurring when monophosphines are used, but the stability of the amine complexes favors the deprotonation of coordinated amine. Instead, the alkoxo complexes may be important in catalytic systems involving chelating ligands [51]. Indeed, the DPPF complex [Pd(DPPF)(p-Bu C6H4)(0-f-Bu) reacted with diphenyl amine, aniline, or piperidine, as shown in Eq. (48), to give the product of amine arylation in high yields in each case [51]. Since, no alkali metal is present in this stoichiometric reaction, the palladium amide is formed by a mechanism that cannot involve external deprotonation by alkali metal base. 

Table VII. Ionization Constants for the Loss of Coordinated Amine Hydrogens from Cu(III)—Peptide Complexes0...

The interchange of the stereochemically significant sec-NH proton in (20) (21) (inversion) or (22) — (23) (isomerization) is a base-catalyzed process and takes place via a deprotonation-protonation mechanism. This interchange is one of the simplest types of reaction of a coordinated ligand , and proton exchange rates have been measured for quite a number of inert transition metal-amine complexes. With suitable central metals (Pt ) or ligands,the deprotonated intermediates can be isolated and characterized. Other reactions of coordinated amine ligands will be considered in Section 7. 

In general, Os complexes are highly effective for the oxidative dehydrogenation of coordinated amine and alcohol... 

Leeuwen and coworkers studied the kinetics for the amination of aryl triflates and bromides using different Xantphos catalyst systems. " For triflate amination, they found the rate to be first order in amine and ferf-butoxide, but zero order in aryl triflate. From this, they concluded that a mechanism similar to the upper pathway in Scheme 7 was operating, with the deprotonation of coordinated amine being the ratedetermining step. For aryl bromides, however, the rate was dependent on the concentration of iert-butoxide, but not amine or aryl bromide. Thus, under these conchtions, the lower pathway-with the replacement of halide by tert-butoxide as the rate-limiting step - was postulated to be the operating mechanism. 

Reductive nitrosylation, on the other hand, can refer to the addition of NO to a metal center Mox with formal reduction of the metal center to yield Mred(NO +), but in the context of ligand reactions reductive nitrosylation refers to the net reactions of NO with metal-bound NO and the ensuing events. Reductive nitrosation of coordinated amines to form nitrosamines occurs through the conjugate base of the amine, and this process has been reported for reactions of NO with [Ni(tacn)2]3 +, 198 with methyl-amine coordinated to a macrocyclic Ni(III) complex,199 with triglycyl complexes of Fe(III), Ni(III), and Cu(III),200 and with Cu(II) macrocyclic complexes.201 Reductive nitrosation of [Ru(NH3)6]3+ produces [Ru(NH3)5N2]2 + with base-catalyzed kinetics the coordinated N2 is produced by hydrolysis after the nitrosation step.170... 

This reaction of Pt(II) is general for a range of coordinated amines apart from ammonia, and appears to yield exclusively the trans geometric isomer (which is called, because of this exclusivity, a stereospecific reaction). Even chelated diamines can be substituted, as they are inevitably more volatile than any anions present thus chelated 1,2-ethanediamine can be replaced by two chloride ions in [Co(en)3]Cl3 to form m-[CoCl2(en)2]Cl, and by... 

Drug Binding to Methionine in Peptides and Proteins Release of Coordinated Amines... 

Ruthenium (III) Ruthenium(III) nitrile complexes [RuLfNHj) ] may be synthesized by reaction of L with [Ru(NH3)50H2], oxidation of [Ru(L)(NH3)j] with Ce or AgV by direct treatment of [RuCl(NH3)5] with L under reflux - or by aerial oxidation of coordinated amines. The IR spectrum of these complexes shows the C=N stretching vibration to occur at higher frequencies than in the free hgand, - indicating net n back-donation from n (L) - d/t (Ru ). This is also reflected in the reactivity of nitrile ligands coordinated to Ru . 

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