Coordinated ligands Acidity

There are a few documented examples of studies of ligand effects on hydrolysis reactions. Angelici et al." investigated the effect of a number of multidentate ligands on the copper(II) ion-catalysed hydrolysis of coordinated amino acid esters. The equilibrium constant for binding of the ester and the rate constant for the hydrolysis of the resulting complex both decrease in the presence of ligands. Similar conclusions have been reached by Hay and Morris, who studied the effect of ethylenediamine... 

Effects of L- -amino acid ligands - Stepping on the tail of enantioselectivity The naturally occurring -amino acids form a class of readily available strongly coordinating ligands, which exhibit broad stmctural variation. Moreover, their availability in enantiomerically pure form offers opportunities for enantioselective catalysis. Some derivatives of these compounds have been... 

Scheme VIII has the form of Scheme II, so the relaxation time is given by Eq. (4-15)—appjirently. However, there is a difference between these two schemes in that L in Scheme VIII is also a participant in an acid-base equilibrium. The proton transfer is much more rapid than is the complex formation, so the acid-base system is considered to be at equilibrium throughout the complex formation. The experiment can be carried out by setting the total ligand concentration comparable to the total metal ion concentration, so that the solution is not buffered. As the base form L of the ligand undergoes coordination, the acid-base equilibrium shifts, thus changing the pH. This pH shift is detected by incorporating an acid-base indicator in the solution.

If deuterio acids are used then ij -HD complexes are formed these are particularly useful in establishing the retention of substantive H-H bonding in the coordinated ligand by observation of a 1 1 1 triplet in the proton nmr spectrum (the proton signal being split by coupling to deuterium with nuclear spin 7 = 1). 

Lewis Acid Catalysis and the Reactions of Coordinated Ligands... 

Likewise, triphenyltin hydride reacts with ethylzinc chloride, or triphenyltin chloride with metallic zinc, to give the compound PhaSnZnCl, which is stable in the presence of a strongly coordinating ligand, but, in its absence, apparently undergoes an intermetallic shift of the organic group, so that protic acids react to liberate benzene (272). 

Some recent interest in the technetium chemistry has been focused on complexes possessing a Tc=N3+ core. Tetrachloronitridotechnetate(VI) complexes can easily be synthesized by the reaction of pertechnetate with sodium azide in concentrated hydrochloric acid [34], Although its square-pyramidal structure resembles that of tetrachlorooxotechnetate(V) complexes, stable character of the nitrido complexes in aqueous solution shows a remarkable contrast to the oxo complexes. However, when a strong acid and a coordinating ligand are absent, the interconversion of di(p-oxo)nitridotechnetium(VI) complexes to the monomeric form occurs in the following complicated manner [35]... 

A series of neutral hexacoordinate phosphorus(v) compounds have been synthesized making use of an acidic phosphorus atom and a coordinating ligand. Compound 39 represents a bicyclic bridgehead phosphorus compound produced <1996IC325>. 

---