Monodentate ligands acids

The use of molybdenum catalysts in combination with hydrogen peroxide is not so common. Nevertheless, there are a number of systems in which molybdates have been employed for the activation of hydrogen peroxide. A catalytic amount of sodium molybdate in combination with monodentate ligands (e.g., hexaalkyl phosphorus triamides or pyridine-N-oxides), and sulfuric acid allowed the epoxidation of simple linear or cyclic olefins [46]. The selectivity obtained by this method was quite low, and significant amounts of diol were formed, even though highly concentrated hydrogen peroxide (>70%) was employed. 

Potentiometric and H-NMR methods were combined in the studies of the interaction of [Pd(en)(H20)2]2+ and [Pd(pic)(H20)2]2+ (pic = 2-picolylamine) with monodentate ligands containing nitrogen or sulfur donor atoms. The ligands represent the side chain residues of nucleic acids and proteins.178... 

Without added acid or nucleophile the lability of the starting compound is very low (<1 x 10"8 s"1) most probably because of the efficient ring-closing process [18]. The second step depends linearly on the pH with a rate constant of 1.61 x 10"4 M 1 s 1. In the presence of added Cl-, the final product of the hydrolysis is m-DDP although the relevance of similar process in vivo was questioned [18]. It has been reported that carboplatin bound to DNA retains the dicarboxylate group, probably as a monodentate ligand [19]. 

Published equilibrium constants for monocarboxylato complexes are summarized in Table VII. All that can be deduced with certainty from these data is that the anions derived from monocarboxylic acids form rather weak complexes with beryllium. In all probability they act as monodentate ligands. The possibility of bidentate chelation using both carboxylate oxygen atoms can be ruled out on the grounds... 

The a-arylation of carbonyl compounds (sometimes in enantioselective version) such as ketones,107-115 amides,114 115 lactones,116 azlactones,117 malonates,118 piperidinones,119,120 cyanoesters,121,122 nitriles,125,124 sul-fones, trimethylsilyl enolates, nitroalkanes, esters, amino acids, or acids has been reported using palladium catalysis. The asymmetric vinylation of ketone enolates has been developed with palladium complexes bearing electron-rich chiral monodentate ligands.155... 

It transpires that most classes of monodentate ligands include members that are able to induce high enantioselectivity in the hydrogenation of the two benchmark substrates 52 a and 53 a. It is not clear whether their corresponding acids 52b and 53 b have been studied or, alternatively, if the authors decided not to include (disappointing) ee-values. For phosphoramidite MonoPhos (29 a), however, the ee-values are invariably excellent. Overall, the TOFs range from 50 to 170 IT1, but have not been optimized in most cases. Unfortunately, with one exception [87], the hydrogenation of dehydroamino esters in which R1 is a (functionalized) alkyl substituent has not been studied, probably because of their difficult accessibility. 

The divalent carbon(O) atom in L C L has two lone electron pairs which makes CL2 a particular class of ligands which may bind as a bidentate Lewis base to one and to two monodentate Lewis acids. The nature of the ligand L determines whether a divalent carbon atom behaves as a carbone or as a carbene. The newly gained insight into the electronic structure of carbones opens a large field for theoretical and experimental research. 

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