Organotellurium ligands — designing and complexation reactions

The possibility of using N-allylcarbothioamide derivatives as well as products of their iodine- and proton-initiated electrophilic heterocyclizations as chelating agents in complexation reactions with Zn(II) and Ag(I) ions is shown. Processing of the obtained experimental data showed that N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids H2L1 – H2L3 and their proton- and iodo-cyclization products HL4, HL5 containing four nucleophilic reaction centers (two oxygen atoms of the carbonyl and hydroxyl groups and N-, S-carbothioamide groups or N-atoms of the dihydrothiazole moiety) are polydentate ligands capable of coordinating with metal ions to form stable six-membered chelate metallocycles. A series of new chelating mono-, bi- and polynuclear complexes Zn(II) and Ag (I) of the composition [Zn2L1,32]n, [Zn2(HL1-3)2(CH3COO)2], [Ag2(HL1,3)2]n, [Zn(HL1-3)2], [Ag(H2L3)2NO3], [Zn(HL4,5)2], K[Ag(HL4,5)2] were synthesized and isolated in solid state. Their molecular structure was established by methods of elemental chemical analysis, NMR 1H, IR and UV-Vis spectroscopy. At a ratio of M:L 1:2, complexes were isolated in which two ligand molecules H2L1 − H2L3 are coordinated to the metal ion by the sulfur atoms of the carbothioamide group and the oxygen of the mono-deprotonated hydroxyl group. It was established that the products of the proton-/iodocyclization HL4, HL5 in the complex formation pass into the thione tautomeric form with coordination through the oxygen atoms of the deprotonated hydroxyl group and nitrogen atoms of the dihydrothiazole heterocycle. At M:L 1:1, binuclear or polynuclear coordination compounds are formed. It was shown that polymerisation in complexes [Zn2L1,32]n and [Ag2(HL1,3)2]n is due to the formation of Zn−(O2SN)−Zn and Ag−O−Ag polymer chains. Investigation of the solubility of the resulting complexes showed that the polymer complexes are weakly soluble or insoluble in DMSO, DMF, while the mononuclear are soluble in methanol, as well as in water.

Download Full-text

Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

10.26434/chemrxiv.6448253.v3 ◽

2018 ◽

Author(s):

Laura Abad Galán ◽

Alexandre N. Sobolev ◽

Eli Zysman-Colman ◽

Mark Ogden ◽

Massimiliano Massi

Keyword(s):

Chelating Ligands ◽

X Ray Diffraction ◽

Reaction Conditions ◽

Claisen Condensation ◽

X Ray ◽

Condensation Products ◽

Complexation Reactions ◽

The Impact ◽

Low Solubility

β-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four β-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by in situretro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensationreaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest that using solvents of lower polarity will mimimise the impact of the retro-Claisen condensation in these complexes.

Download Full-text

The Aqueous Thermodynamics and Complexation Reactions of Anionic Silica and Uranium Species to High Concentration

10.2172/835470 ◽

2003 ◽

Author(s):

Gregory R Choppin

Keyword(s):

High Concentration ◽

Complexation Reactions ◽

Uranium Species

Download Full-text