Monodentate ligands carboxylic acids

The complexes of aromatic hydroxy carboxylic acids (salicylic acid and its isomers) with [Bu2Sn(IV)] and [Ph3Sn(IV)] were obtained. The FT-IR and Raman spectra clearly demonstrated that the organotin(IV) moieties react with the O, O) atoms of the ligands. It was found that in most cases the -COO group chelated to the central atoms, but monodentate coordination was also observed. The complexes probably have polymeric structures. 

L-piperidine-2-carboxylic acid is a non-proteinogenic amino acid that is a metabolite of lysine. The zinc complexes of DL-piperidine-2-carboxylic acid, DL-piperidine-3-carboxylic acid, and piperidine-4-carboxylic acid have been studied. The X-ray crystal structures have been determined for the latter two. [ZnCl2(DL-piperidine 3-carboxylate)2] (42) is monomeric with a tetrahedral metal center and monodentate carboxylates. [Zn2Cl4(piperidine-4-carboxylate)2] (43) contains two bridging carboxylates in a dimeric structure. IR studies suggest that the DL-piperidine-2-carboxy-lato zinc has monodentate carboxylate ligands coordinating.392... 

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... 

Alkylphosphonate groups are monodentate donors of intermediate hardness that may replace carboxylate groups in chelating agents such as nitrilotriacetic acid (NTA), ethylenediaminetetra-acetic acid (EDTA), and diethylenetriaminepentaacetic acid (DTPA). The corresponding ligands nitrilotrimethylenephosphonic acid (NTP), 1, ethylenediaminetetramethylenephosphonic acid (EDTP),... 

The most numerous complexes of this stoichiometry are the bis(carboxylato) complexes. They can be obtained from the reaction between [Rh(N0)Cl(N02)(PPh3 ] and carboxylic acids in aerated solution (equation 31 1).127,1308 The IR spectra of the carboxylato ligands (Table 92) are consistent with their monodentate bonding shown in the structure (136).1328... 

Treatment of nF salts with acetic acid affords trans-[Ni(02CMe)2(H20)4] (79) incorporating monodentate acetate ligands. By altering the reaction conditions and the carboxylic acid, complexes of type trans andcri [Ni(02CR)2(L)2]... 

We see that only complexes with formation constants of the order of 106 M-1 or more will lead to titration curves with a sufficiently steep change in pL near the equivalence point (at CM VM / CL VL = 1) to be useful for volumetric analysis. None of the common monodentate ligands, such as the halide anions (Cl-, Br , I-) or the pseudohalides (CN , SCN-, N3 ), form such strong complexes, nor do the carboxylic acid anions (such as acetate) or ammonia (NH3). However, in section 5.2 we will encounter special ligands, the chelates, that do form sufficiently strong 1 1 complexes. 

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