Hydrogen coordinated amine

Intramolecular Hydrogen Bonding from Coordinated Amine to Uncoordinated Phosphate Group... 

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

Note Deprotonation of the palladium coordinated amine is difficult and dependant upon the choice of base. Sodium hydride is a strong base and upon abstraction of a proton produces molecular hydrogen, which evolves from the reaction without reacting with the palladium centre. 

He also pointed out 12 possible N—H- -F—C hydrogen bonds [2]. The hydrogen bond donors (N—H) among these could roughly be classified into four N—H of amides (6) (Scheme 4.5), Lewis acid coordinated amine (8), aniline (10), and ammonium (9). Howard et al. showed another hydrazine proton donor (7) [23]. All these have acidic amino protons and thus could protonate negatively charged organic fluorine atoms. 

The immediate product from the reaction of the hydride complex with ketone has been a subject of debate. Some have proposed that an alkoxide complex is formed and that proton transfer between the coordinated amine and the alkoxide then forms the alcohol that is ultimately released. Others have supported a direct transfer to form free alcohol (or amine) and then coordination of this species to the open To accommodate the isotope effect data and the absence of an open coordination site for coordination of the ketone, the formation of the alkoxide from the hydride has been proposed to occur by hydride transfer assisted by hydrogen bonding of the amine in the case of the reactions with [Ru(BINAP)(diamine)(H)j], or by ring slip to allow coordination of the ketone (or imine) in the case of the reactions with the Shvo catalyst. ... 

Detailed studies of the stereochemistry of the cyclization process indicate that a second amine is likely coordinated to the metal center during the insertion process and primary KIE values for N-H and N-D suggest that protonolysis occurs in concert with insertion. A possible mechanism that was proposed to account for this role of a second amine is showm in Equation 16.94. Hydrogen bonding between this coordinated amine and the amido complex is proposed to accelerate the insertion step. 

It is well known from classical organometallic chemistry that non-coordinating amine bases affect the behavior of H2 complexes [44]. The azadithiolate motif has been exploited in the design of new catalysts for hydrogen oxidation, as described in the next section on [NiFe] hydrogenases [45]. 

Incorporation of this coordinative amine ligand within the cycle structure is an alternative approach for generating stable macrocycles. In this regard, alkyl bridged bis(2-hydroxyphenylmethyl) amines have been reacted with 4,4 -biphenyldiboronic acid (Fig. 19a). Esterification proceeds with concomitant coordination of the amine to the resulting ester. The paraquat dication is complexed by this assembly in a 1 1 manner (Fig. 19b) through ionic interactions (anionic boronate with pyridyl cation), attractive n-n interactions (between biphenyl components) and C —H —O hydrogen bonds (paraquat... 

Some examples of the use of a temporary additional site of coordination have been published. Burk and Feaster have transformed a series of ketones into hydrazones capable of chelating to a rhodium catalyst (Scheme 4.7). Upon coordination, enanti os elective hydrogenation of the hydrazone is feasible, yielding N-aroylhydrazines in up to 97% ee. Finally, the hydrazines were transformed into amines by treatment with Sml2. 

The assumed transition state of this reaction is shown in Scheme 5.3. Yb(OTf)3, (J )-(-h)-BINOL, and DBU form a complex with two hydrogen bonds, and the axial chirality of (J )-(-h)-BINOL is transferred via the hydrogen bonds to the amine parts. The additive would interact with the phenolic hydrogen of the imine, which is fixed by bidentate coordination to Yb(III). Because the top face of the imine is shielded by the amine, the dienophiles approach from the bottom face to achieve high levels of selectivity. 

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