Trichloroacetate ligands

I. Referring to an unstable and/or transient chemical species. 2. Referring to a substituent, atom, or group of a molecular entity that is easily removable e.g., the labile proton of the carboxyl group in trichloroacetic acid. 3. In reference to coordinator complexes, referring to ligands that can be readily replaced by other ligands. 4. On occasions, the term is also used with respect to stable, yet reactive, chemical species. 

Thus a detailed study on the effect of ligands that stabilize copper(I) on the rates and mechanisms of reduction of trichloroacetic acid, CI3CCO2 was carried out (149). 

The general reaction mechanism for the reaction of Cu(I) with trichloroacetic acid in the presence of stabilizing ligands is summarized in the following equations (149) ... 

NMR studies of the mixed carboxylates containing acetates and trichloroacetates have indicated that ligand scrambling reactions occur in solution although all of the species were isolated, and isomerization possibilities occur, no discrete isomers were identified.329 Gas... 

Mo(CO)6 was also used to catalyze Kharasch addition reactions of tetrachloro-methane or trichloroacetates to terminal olefins in acetonitrile (Fig. 38) [218]. A precomplexation like for Cr(CO)6 was not necessary. The ligand exchange... 

A recent study showed that 152 behaves mechanistically different from other catalysts in addition reactions of more activated halides 140, such as trichloroacetate to styrene [222]. After initial reduction to Ru(II), chlorine abstraction from substrates 140 is in contrast to all other ruthenium complexes not the rate limiting step (cf. Fig. 36). ESR spectroscopic investigations support this fact. The subsequent addition to styrene becomes rate limiting, while the final ligand transfer step is fast and concentration-independent. For less activated substrates 140, however, chlorine abstraction becomes rate-determining again. Moreover, the Ru(III) complex itself can enter an, albeit considerably slower Ru(III)-Ru(IV) Kharasch addition cycle, when the reaction was performed in the absence of magnesium. This cycle operates, however, for only the most easily reducible halides, such as trichloroacetate. 

Not only trichloroacetate or trichloroacetamide systems can be applied. Weinreb and coworkers reported a few copper-catalyzed 5-exo ATRC of 2,2-dichloro-3-oxo-6-heptenoates using 3.2 mol% CuCI and PPh3 as a ligand [304]. A 1.6 1 mixture of regioisomeric 5-exo and 6-endo products was obtained with low diastereoselectivity. 5-exo Annulations and 6-exo cyclizations gave the products with 1 and 2.7 mol% Cu catalyst in 82-99% and 91% yield, respectively. Ghelfi and colleagues found that dichloroacetaldehyde-derived mixed 0-allylic acetals served... 

Cu(l) and Fe(ll) complexes prepared in situ by reacting copper(l) or iron(ll) chloride with 1 equiv of ligand LI (tris(pyridin-2-ylmethyl)amine) or L2 are efficient catalysts for atom-transfer radical addition reactions. For instance, pent-4-enyl trichloroacetate was converted into 3,3,5-trichlorooxocan-2-one in 90% and 99% yield, respectively, when CuCl-Ll and CuCl-L2 were used as catalysts (Scheme 30) <2000J(P1)575>. 

The first step is diffusion controlled while the second represents the formation of an outer sphere complex in which the metal ion and the ligand are separated by at least one molecule to water. In the final step, this outer sphere complex ejects the water and forms an inner sphere complex in which the metal and ligand are directly associated. Some ligands cannot displace the water and complexation apparently terminates with the formation of the outer sphere complex. Plutonium cations form both inner and outer sphere complexes, depending on the ligand pK. For trivalent plutonium, we can assign a predominant outer sphere character to the halide, nitrate, sulfonate and trichloroacetate complexes and an inner sphere character to the fluoride, iodate, sulfate and acetate complexes (23). A study of Am , Th and complexation... 

The use of bipy or terp as the auxiliary ligand can also lead to the formation of the monomeric or dimeric structures. In [PrL3(bipy)2] (HE = trichloroacetic acid) [42], the three carboxylates chelate (ti ) to Pr(III), whereas the two bipy coordinate to the metal center with their two nitrogen atoms. [TbE3(terp)(H20)]2 (E = 4-aminobenzonic acid) is a dimer, where the... 

Wang, J.D.N., Wu, G., and Zheng, P. (1991) Studies on complexes of rare earths with bidentate heterocyclic amine ligands. III. Synthesis, properties and crystal structure of complexes of lanthanide trichloroacetate with two a, a, -bipyridines. Gaodeng Xuexiao Huaxue Xuebao, 12 (10), 1284-1288. 

When diphenyl tellurium bis[trichloroacetate] was refluxed in dichloromethane with 4-methylpyridine, tetramethylpiperidine, or dimethylacetamide, 1 1 adducts of diphenyl tellurium dichloride with these ligands were isolated". ... 

Fig. 5 Mixing di- and tripyridyl ligands (7-11) with Pd(en) produces a diverse dynamic combinatorial library of cyclic and cage coordination compounds. Exposure of this library to sodium trichloroacetate (12) results in the amplification of a new receptor. (Adapted from Ref. [17].)...

A novel type of diorganotin carboxylate, 158, has been obtained with trichloroacetic acid the compound ]Bu4Sn2(02CCCl3)3(jM-OH)] contains one Sn-OH-Sn bridge (Sn-O 2.031 and 2.113 A), one bridging carboxylato group (Sn-O 2.255 and 2.278 A) and two monodentate carboxylato ligands [499]. The phenyl derivative... 

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