Search

In a present paper methods of concentration of Ce(III) from aqueous solutions onto synthetic polymer adsorbent. The sorption-photometric determination of the microquantities of cerium ions by new polymeric chelating sorbent, modified with dithizone has been studied. Sorption process was carried out under static conditions. Optimal characteristics of the sorption process: influence of pH, time of contact, effect of the initial concentration of metal, influence of ionic strength were studied. pH for extracting Ce is 5; the residence time is 210 min. Optimal ionic strength was achieved at a value of μ =0.6. The sorption capacity of the sorbent and the percentage recovery were determined from the difference in the initial and final concentrations of cerium(III) in the solution. The sorbability of cerium(III) ions was 91.38%, sorption capacity of sorbent with respect to cerium ions is 682.85 mg∙g-1. At the final stage, a desorption process was carried out using different (organic and mineral) acids with the same concentrations (0.5, 1.0, 1.5, and 2.0 M). 1M HCl has the highest eluting ability with respect to cerium (III) ions. Sorbent modified with dithizone based on a styrene-maleic anhydride (SMA) copolymer is proposed as synthetic sorbent with the best analytical properties (high sorption capacity, residence time 3 h with respect to cerium ions). Multiple use of the regenerated sorbent for concentration is possible. The developed techniques can be used to determine Ce(III) in standard samples, soil and tap water.

Two known lanthanide complexes, [KLa(HL 1 ) 2 {(CH 3 ) 2 NCHO} 2 (H 2 O) 3 ] ( 1 ) and [Sm(H 2 O) 9 ]( E -H 2 L 2 ) 3 ·2H 2 O ( 2 ) were prepared by reaction of lanthanum(III) and samarium(III) nitrates with potassium 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonate (KH 2 L 1 ) and potassium ( E,Z )-5-chloro-3-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonate (KH 2 L 2 ), respectively. Catalytic activities of 1 and 2 were evaluated in the cyanosilylation of aldehydes with trimethylsilyl cyanide in different solvents such as tetrahydrofuran, dichloromethane or methanol. Complex 1 was found to be efficient catalyst for the cyanosilylation reaction in methanol medium at room temperature, producing cyanohydrin trimethylsilyl ethers with good yields (76–99%).

A series of known metal complexes, [LaL2(NO3)(H2O)2]·5H2O (1), [Zn(μ-L)(NO3)(H2O)]n (2), {[Cd2(μ-HL)(μ-L)(NO3)3(H2O)]·H2O}n (3) and [Hg(μ-L)(N3)]n·nH2O (4), were synthesized from the corresponding metal salts and 2-pyridinecarboxaldehyde isonicotinoylhydrazone (HL), and demonstrated high activity and selectivity in the cyanosilylation of aldehydes. Although all the complexes are derived from the same HL hydrazone ligand, the catalytic activity of 1–4 is different and relates to the metal center and coordination environment, whereas complex 1 being the most effective homogeneous Lewis acid-base catalyst towards the synthesis of cyanohydrin trimethylsilyl ethers from both aliphatic and aromatic aldehydes with yields up to 96.3 % in 6 h in methanol solution and at room temperature. According to the proposed mechanism, both coordination and noncovalent interactions (hydrogen and tetrel bonds) play a significant role and account for the higher catalytic activity of complex 1.

Two complexes [KLa(HL(1))2{(CH3)2NCHO}2(H2O)3] (1) and [Sm(H2O)9](E-H2L(2))3·2H2O (2) were synthesized by the reaction of lanthanum(III) and samarium(III) nitrates with potassium 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonate (KH2L(1)) and potassium (E,Z)-5-chloro-3-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonate (KH2L(2)), respectively. Both complexes were fully characterized by elemental analysis, IR, (1)H and (13)C NMR spectroscopy, ESI-MS and single-crystal X-ray diffraction. Cooperative E,Z→E isomerization of KH2L(2), induced by resonance assisted hydrogen bonding and ionic interactions, occurs upon the interaction with Sm(III). Catalytic activities of KH2L(1,2) and their lanthanide derivatives were evaluated in the Henry reaction of nitroethane with a variety of aromatic and aliphatic aldehydes. Good yields (up to 91%) and diastereoselectivities (syn/anti 3 : 1) were observed in the reactions catalyzed by 1 in water.