Proton exchange amine ligands

Proton electrochemical gradient. 6,714 Proton exchange amine ligands, 2, 24 Proton loss catalysis... 

Propionohydroxamic acid metal complexes, 506 Propylenediamine metal complexes, 34 Protactinium complexes cupferron, 510 Proteins electron transfer active sites, 525 metal complexes, 759-774 binding sites, 769,771 naturally occurring, 974 occurrence, 962 Proton exchange amine ligands, 24 Protonolysis metal alkoxides, 352 Prussian blue, 7, 8 Pseudocubanes structure... 

The mechanism provides (in equation 1) a pathway for proton exchange in amine complexes. (In fact, it was the observation that proton exchange in [Co(NH3)6]3+313 and the base hydrolysis of (Co(NH3)5Br]2+298 had the same kinetic form that led Garrick to propose this mechanism in 1937.314) The pathway for base catalyzed solvolysis is made up of (1) + (2) + (3) and the pathway for base catalyzed substitution is (1) + (2) + (4). It was the observation of base catalyzed ligand substitution that provided the first strong evidence for the dissociative nature of the process.315... 

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. 

Much of the reactivity of amido ligands involves proton exchange processes that eliminate amine. The exchange is believed to occur by an associative mechanism consequently, the rate of reaction decreases for sterically congested metal complexes. For example, treatment of V[N(CH3)2]j with terf-butanol at room temperature forms V(O-f-Bu) in good yield, while at this temperature the more encumbered complex W[N(CH3)2] reacts only slowly with methanol and ethanol, and not at all with tert-butanoV° The use of bulky N-alkyl substituents allows for the isolation of low-coordinate complexes, such as Cr[N( -Pr)2]3- Amido complexes derived from primary amines can also serve as precursors to imido complexes. In many cases, amido halide complexes form imido complexes by loss of hydrogen chloride in the presence of a base (Equation 4.17). ... 

Polymeric amines can be proton acceptors, acyl transfer agents, or ligands for metal ions. The 2- and 4-isomers of poly(vinylpyridine) (11) and (12) and the weakly basic ion exchange resins, p-dimethylaminomethylated PS (2) and poly(2-dimethylaminoethyl acrylate), are commercial. The ion exchange resins are catalysts for aldol condensations, Knoevenagel condensations, Perkin reactions, cyanohydrin formation and redistributions of chlorosilanes. " The poly(vinylpyridine)s have been used in stoichiometric amounts for preparation of esters from acid chlorides and alcohols, and for preparation of trimethylsilyl ethers and trimethylsilylamines from chlorotrimethylsilane and alcohols or amines. Polymer-suppored DBU (l,8-diazabicyclo[5.4.0]undec-7-ene) (52) in stoichiometric amounts promotes dehydrohalogenation of alkyl bromides and esterification of carboxylic acids with alkyl halides. The protonated tertiary amine resins are converted to free base form by treatment with aqueous sodium hydroxide. 

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