EXTRACTION OF IRON(II) BY 2-(2'-THIAZOLYLAZO)-4,6-DIMETHYLPHENOL AND 2-(4',5'-DIMETHYL-2'-THIAZOLYLAZO)-4,6-DIMETHYLPHENOL

The extraction of Fe(II) from 0.1M NaClO₄. by 2-(2'-thiazolylazo)-4,6-dimethylphenol (TADMP) and 2-(4 ', 5'-dimethy1-2’-thiazolylazo)-4,6-dimethylphenol (DMTADMP) dissolved in chloroform has been studied by distribution methods. The experimental data, treated by both graphical and numerical methods, may be explained by assuming the formation of the species FeRClO₄. (logK₁₀₁₁ = 7.58±0.09 and 9.58±0.10) and FeR₂ logK₁₀₂₀. = 14.31±0.22 and 15.32±0.18) for Fe(II)-TADMP and Fefll)-DMTADMP systems, respectively.     

Synthesis,crystal structure of copper(II) complexes comprising 2-(biphenylazo)phenol and 1-(biphenylazo)naphthol ligands and their catalytic activity in nitroaldol reaction

New series of copper(II) complexes of the type [Cu(L)₂] (L = L₁–L₅) comprising bidentate 2-(biphenylazo)phenol (HL₁–HL₄) and 1-(biphenylazo)naphthol (HL₅) ligands have been synthesized. The composition of complexes and ligands (HL₁–HL₄) has been established by elemental analysis and spectral (FT–IR, UV–Vis, ¹H NMR and EPR) methods. Molecular structures of copper complexes [Cu(L₃)₂] (3) and [Cu(L₅)₂] (5) were established by X-ray crystallography. These Copper(II) biphenylazo complexes exhibit a very good catalytic activity towards nitroaldol reaction of various aldehydes with nitromethane.     

Synthesis of Pd(II) coordination complexes of (S)-4-isobutyl-2-methyl-2-oxazoline and (S)-2-(2,2-dimethylpropyl)-4-isopropyl-2-oxazoline

(S)-4-Isobutyl-2-methyl-2-oxazoline (1) was obtained from ethyl acetimidate hydrochloride and l-leucinol in 81% yield. (S)-2-(2,2-Dimethylpropyl)-4-isopropyl-2-oxazoline (2) was synthesized from 3,3-dimethylbutyryl chloride and l-valinol in two steps in a total yield of 44%. Reactions of oxazolines 1 and 2 with Pd(OAc)₂ in AcOH or MeCN at different temperatures followed by treatment with LiCl resulted in the formation of the corresponding coordination complexes PdCl₂(1)₂ and PdCl₂(2)₂ with no traces of cyclopalladated complexes.     

1-(Pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole and its copper(II) complex as a new fluorescent sensor for dopamine (4-(2-aminoethyl)benzene-1,2-diol)

A new ligand 1-(pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole (L) and its Cu(II) complex (1) have been synthesized and characterized spectroscopically and structurally. The Cu(II) ion is coordinated by two nitrogen atoms of benzimidazole groups, two oxygen atoms of the nitrate anions and one oxygen atom of a water molecule forming distorted trigonal bipyramidal geometry. The ligand and its complex have been utilized as a fluorescent sensor for 4-(2-aminoethyl)benzene-1,2-diol. A plot of F₀/F − F₀ vs 1/Conc (4-(2-aminoethyl)benzene-1,2-diol) at a selected wavelength of 306 nm with (L) that shows a straight line behavior, supports the validity of the assumption of 1:1 complex formation and the association constant of (L) with 4-(2-aminoethyl)benzene-1,2-diol is calculated to be 9868 M^− 1. Sensor (L) is found to be selective for 4-(2-aminoethyl)benzene-1,2-diol over aromatic amines, phenols, amino catechol (L-3,4-dihydroxyphenylalanine) and 4,6-ditertiarybutyl benzene-1,2-diol.     

Synthese von 1-(β-D-Arabinofuranosyl)-pyrimidinen

Syntheses of 1-(β-D-Arbinofuranosyl)-pyrimidines New synthetic methods of 1-(β-D-arabinofuranosyl)-pyrimidines are described. 1-(β-D-arabinofuranosyl)-uracil, 1-(β-D-arabinofuranosyl)-5-fluorouracil, 1-(β-D-arabinofuranosyl)-thymine, and 1-(β-D-arabinofuranosyl)-cytosine can be obtained in a high yield by the splitting of the anhydrobond in 2,2′-anhydropyrimidines in dipolar aprotic solvents, such as HMPT, DMF, and DMSO, respectively, in the presence of activated elemental copper. Unlike the formation of cyclopyrimidiens ribonucleosides are directly transformed to the corresponding arabinofuranosyl derivatives by the reaction with diphenylcarbonate and NaHCO₃ in the presence of copper. The reaction proceeds probably via an intermediate formation of the cycloproduct. Further aspects on the mechanism are described.     

Organic reagents for removing heavy metals from a 10-34-0 (N-P2O5-K2O) grade fertilizer solution and wet-process phosphoric acid

Fertilizer solutions and wet-process phosphoric acid (WPA) contain heavy metal impurities such as cadmium, zinc, lead, copper, manganese, and chromium. Trisodium trithiocyanuric acid (TMT-15), sodium trithiocarbonate (5% Na₂CS₃), and sodium polythiocarbonate (Thio-Red II) were evaluated as precipitating agents for heavy metals in a 10-34-0 (N-P₂O₅-K₂O) grade fertilizer solution and WPA. A water-insoluble starch xanthate was also evaluated as an adsorbent for the heavy metals in 10-34-0 (N-P₂O₅-K₂O) and WPA. Arsenic (24–99+%), cadmium (36–97+%), copper (98+%), mercury (96+%), lead (83–88+%), and zinc (8–83+%) precipitated from 10-34-0 (N-P₂O₅-K₂O) upon the addition of each organic reagent, while levels of manganese and chromium were unaffected. Mercury (97+%), lead (75+%), cadmium (11–38%), copper (99+%), and chromium (3–35%) precipitated from WPA upon the addition of 5% Na₂CS₃ and Thio-Red II, while precipitation of manganese and zinc was negligible. The water-insoluble starch xanthate adsorbed mercury (96+%), copper (38–98+%), and lead (24–75%) from 10-34-0 (N-P₂O₅-K₂O) and WPA while adsorption of arsenic, cadmium, manganese, chromium, and zinc was negligible.     

Regioselective oxidation and halogenation of 2-(arylsulfenylimino)- and 2-(arylsulfinylimino)-4-thiazolines

The synthesis of 4-thiazoline 2-iminium sulfinates ( 3 ) is described. From the salts 3 and NBS the 2-(arylsulfonylimino)-4-thiazolines ( 4 ) were formed, which have also been prepared by oxidation of 2-(arylsulfenylimino)-4-thiazolines ( 5 ) and by reaction of the arylsulfonyl chlorides ( 6 ) with 2-imino-4-thiazolines ( 2 ). The treatment of 5 with NBS (or NIS) in dry solvents results in 2-(arylsulfenylimino)-5-bromo (or iodo)-4-thiazolines ( 7 ); in the presence of NaHCO₃ 2-(arylsulfonylimino)-5-bromo-4-thiazolines ( 8 ) are formed. 2-(Arylsulfinylimino)-4-thiazolines ( 10 ) have also been halo- genated in the same manner with NBS or NIS to give the products ( 11 ).     

The first example of Cu(I) complex with 5-pyrazolyl-2-thioxotetrahydro-4H-imidazol-4-one: Synthesis and structural characterization

A new organic ligand 3-phenyl-5-((Z)-1,5-diphenyl-pyrazol-3-yl)methylene)-2-methylthio-4,5-dihydro-imidazol-4-one (L) has been synthesized by a two step reaction sequence starting from 3-phenyl-2-thiohydantoin and 3-formyl-pyrazoline. The complex of copper(I) with L₂СuClO₄ composition was obtained by the reactions of this ligand with Сu(ClO₄)₂·6H₂O; thus, the reduction of copper(II) took place during the complex formation. The crystal structure of synthesized complex has been determined by X-ray analysis. Copper atom has a distorted tetrahedral ligand environment and coordinated by four nitrogen atoms of two ligand moieties; perchlorate ion does not participate in the coordination of the metal ion. This complex undergo reversible electrochemical reduction at − 0.32 V.     

2-(2′-乙酰氧基-5′-溴甲基苯基)-2H-苯并三唑的合成

2-(2′-羟基-5′-甲基苯基)-2H-苯并三唑(UV-P)经过羟基乙酰化、N-溴代丁二酰亚胺(NBS)溴代,合成了具有高反应活性的2-(2′-乙酰氧基-5′-溴甲基苯基)-2H-苯并三唑。为提高目标产物产率和反应效率,分别对溶剂、引发剂、反应温度、反应时间、反应物投料比和反应底物浓度进行了研究。得出较优合成条件为:氮气保护下,四氯化碳为溶剂,偶氮二异丁腈(AIBN)引发,NBS与2-(2′-乙酰氧基-5′-甲基苯基)-2H-苯并三唑摩尔比1∶1,回流反应1h。在上述条件下,2-(2′-乙酰氧基-5′-溴甲基苯基)-2H-苯并三唑产率为60%。产物经过IR、1HNMR、MS分析证明结构正确。     

2-[1-(2,6-Dibenzhydryl-4-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridyliron(II) dichlorides: Synthesis,characterization and ethylene polymerization behavior

A series of 2-[1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine ligands (L1–L5) as well as the ligand 2,6-bis[1-(2,6-dibenzhydryl-4-chloro-phenylimino)ethyl]pyridine (L6) were synthesized and reacted with FeCl₂·4H₂O to afford the iron(II) dichloride complexes [LFeCl₂] (Fe1–Fe6). All new compounds were fully characterized by elemental and spectroscopic analysis, and the molecular structures of the complexes Fe1, Fe2 and Fe4 were determined by single-crystal X-ray diffraction, which revealed a pseudo-square-pyramidal geometry at iron. Upon activation with either MAO or MMAO, all iron pre-catalysts exhibited very high activity in ethylene polymerization with good thermal stability. To the best of our knowledge, the current system showed the highest activity amongst iron bis(imino)pyridine pre-catalysts reported to-date. The polymerization parameters were explored to determine the optimum conditions for catalytic activity, which were typically found to be 2500 eq. Al to Fe at 60 °C in the presence of MMAO, and 80 °C in the presence of MAO. The resultant polyethylene possessed a narrow molecular polydispersity index (PDI) consistent with the formation of single-site active species.     

Electrochemical and surface analytical studies of the self-assembled monolayer of 5-methoxy-2-(octadecylthio)benzimidazole in corrosion protection of copper

5-Methoxy-2-(octadecylthio)benzimidazole (MOTBI) monolayer was self-assembled on fresh copper surface obtained after etching with nitric acid at ambient temperature. The optimum conditions for formation of self-assembled monolayer (SAM) were established using impedance studies. The optimum conditions are methanol as solvent, 10 mM concentration of the organic molecule and an immersion period of 24 h. The MOTBI SAM on copper surface was characterized by contact angle measurements, X-ray photoelectron spectroscopy and reflection absorption FTIR spectroscopy and it is inferred that chemisorption of MOTBI on copper surface is through nitrogen. Corrosion protection ability of MOTBI SAM was evaluated in aqueous NaCl solution using impedance, electrochemical quartz crystal nanobalance, potentiodynamic polarization and weight-loss studies. While bare copper showed a charge-transfer resistance (R_ct) value of 1.89 kΩ cm² in 0.20 M NaCl aqueous environment, the R_ct value for SAM covered copper surface is 123.4 kΩ cm². The MOTBI SAM on copper afforded corrosion inhibition efficiency of 98-99% in NaCl solution in the concentration range and in the temperature range studied. The SAM functions as a cathodic inhibitor. Quantum chemical calculations showed that MOTBI has relatively small ΔE between HOMO and LUMO and large negative charge in its benzimidazole ring, which facilitate formation of a polymeric [Cu⁺-MOTBI] complex on copper surface.     

Copper(II) and cadmium(II) complexes with an imide tethered imidazole and a copper(II) coordination polymer through ring opening reaction

The reactions of 2-(3-(1H-imidazol-1-yl)propyl)isoindoline-1,3-dione (L) with copper (II) chloride or copper(II) nitrate resulted in mononuclear complexes [CuL₄Cl₂]·12H₂O (1) or [CuL₄(H₂O)NO₃]NO₃·2H₂O (2) respectively; whereas the copper(II) acetate reacted with L to give a three dimensional coordination polymer {[Cu(L′)₂]·4H₂O}n (3), (where L′ = 2-(3-(1H-imidazol-1-yl)propylcarbamoyl)benzoate). The reaction of cadmium(II) acetate with L led to the formation of a seven-coordinated complex [CdL₃(O₂CCH₃)₂]·2H₂O (4).     

Anodic oxidation of 3-amino-5-(pyrid-4-yl)-1, 2-dihydropyrid-2-one (amrinone)

The anodic behavior of the cardiotonic drug 3-amino-5-(pyrid-4-yl)-1,2-dihydropyrid-2-one 1 and of 6 compounds with similar structure was investigated at platinum and vitreous carbon electrodes in acetonitrile and in aqueous medium. Caused by the 3-amino group 1 is oxidized at a relatively small oxidation potential in an irreversible two-electron process. Depending on the addition of a strong base or a strong acid the oxidation potential vs. SCE in acetonitrile is −0.08 V (anion), +0.66 V (neutral compound), +0.93 V (monocation) or +1.15 V (dication). In H₂O a strong decrease of the oxidation potential with increasing pH was found as a reason for the sensitivity of 1 against oxygen in alkaline solution. The anodic oxidation of 3-dimethylamino-5-(pyrid-4-yl)-1, 2-dihydro-pyrid-2-one 3 in 0.1 m H₂SO₄ leads to 5-(pyrid-4-yl)-piperidine-2,3,6-trione 9a or 5-(pyrid-4-yl)-piperidine-2,3,4-trione 9b , which is also the oxidation product of 1 at small concentration. At high concentration of 1 coupling reactions at the 3-amino-group lead to dimeric products, which could not be identified.     

Furanderivate. VII. 2-[Furyl-(2)- und 5-Nitro-furyl-(2)]vinylphosphonsäure-O,O-diethylester

Furanderivatives. VII. O,O-Diethyl-2-[furyl-(2)- and 5-nitro-furyl-(2)] vinylphosphonates Syntheses and spectroscopic properties (i.r., u.v., ¹H-, and ¹³C-n.m.r.) of the title compounds existing as E-isomers with the general structure 1–8 (R⁵  H, NO₂; R  CN, COOEt, H, NMe₂) are represented. According to spectroscopic data the compound 8 (R⁵  NO₂; R  NMe₂) differs in its electronic structure.     

Coexistence of two distinct axial ligands and their thermo-induced substitution in trans-[FeL2(NCS)2][FeL2(CH3OH)2](NCS)2 (L = 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole)

A novel iron(II) complex, trans-[FeL₂(NCS)₂][FeL₂(CH₃OH)₂](NCS)₂ (1) with 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole (L) has been successfully synthesized and characterized. X-ray crystallography analysis shows that 1 is the first example in the mononuclear triazole-based complexes consisting of two distinct molecules: trans-[FeL₂(NCS)₂] and trans-[FeL₂(CH₃OH)₂](NCS)₂ with each octahedral iron(II) center coordinated axial by two NCS⁻ ions in Fe1 but two MeOH molecules in Fe2. Moreover, 1 can lose two MeOH molecules at 220 °C to form trans-[FeL₂(NCS)₂] (2) which can be transformed to 1 when recrystallizing 2 in methanol. Both 1 and 2 are high-spin species in the range of 1.8–300 K.     

Copper(II) complexes with acetone picolinoyl hydrazones: Crystallographic insight into metalloligand formation

Complexes with free donor atoms, termed metalloligands, are important building blocks in the stepwise approach towards mixed-metal organic frameworks. In this work, the possibility of a metalloligand formation from nicotinic or isonicotinic acid hydrazides and copper(II) centers, is assessed. Syntheses, X-ray crystal structures and spectroscopic properties of two new copper(II) compounds with acetone 3- and 4-picolinoyl hydrazones are reported. The structural studies reveal the formation of a mononuclear cationic metalloligand in [Cu(Hisn)₂](NO₃)₂ (1) with a zwitterionic acetone isonicotinoyl hydrazone (Hisn), as well as a neutral, layered (2D) coordination polymer, [Cu(μ-nic)₂]_n (2), with a deprotonated acetone nicotinoyl hydrazone (Hnic). Heteroatom position in the hydrazide precursor and copper salt acidity influence the formation of pure products.     

A selective and convenient synthesis of 2-(bis(2-hydroxyethyl)amino)ethyl alkanoate over mixed metal oxides

Esterification reactions carried out using various mineral acids are threat to environment hence process modification using commercially viable heterogeneous catalysts are in demand. In current work, the esterification of tri-ethanolamine (TEA, C₆H₁₅O₃N) with several fatty acids in liquid phase has been investigated on a series of heterogeneous mixed metal oxides catalyst prepared by co-precipitation method, crystallizing with spinel lattice such as, CuFe₂O₄, ZnFe₂O₄, CoFe₂O₄, NiFe₂O₄ and 10% (w/w) ZnFe₂O₄ supported on SiO₂ and ZrO₂. The best catalyst for the selective preparation of 2-(bis(2-hydroxyethyl)amino)ethyl alkanoate was 10% (w/w) ZnFe₂O₄ supported on ZrO₂. Detail comparison of a 10% (w/w) ZnFe₂O₄/ZrO₂ prepared by co-precipitation method was carried out with 10% (w/w) ZnFe₂O₄/ZrO₂ prepared by template route for the selective formation of 2-(bis(2-hydroxyethyl)amino)ethyl alkanoate. The effects of variety of parameters including effect of catalyst preparation were studied in a batch reactor.     

First zinc complex of an amino acid pyrazole conjugate: synthesis and crystal structure of {Zn[3-(Ac-Phe)-5-methyl-pyrazole]2}2(ClO4)4

The zinc(II) complex, of the dimeric {Zn[3-(Ac-Phe)-5-methyl-pyrazole]₂}₂(ClO₄)₄ (5) was obtained by the reaction of the amino acid–pyrazole conjugate, 3-(Ac-Phe)-5-methyl-pyrazole (4) and Zn(ClO₄)₂. An acetone solvate of this complex was analyzed by single crystal X-ray crystallography, which establishes the dimeric nature of the complex with a large Zn–Zn separation of 5.551(6) Å and exbihiting coordination to the distorted trigonal bipyramidal zinc centers through the amino acid CO and the pyrazole N.     

Synthesis, Spectroscopic Characterization and Structures of Tributyltin(IV) 4-[((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]benzoates. Toxicity Studies on the Second Larval Instar of the Anopheles stephensi Mosquito Larvae

A series of tributyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]benzoates have been investigated by ¹H, ¹³C, ¹¹⁹Sn NMR, IR and ¹¹⁹Sn M?ssbauer spectroscopic techniques in combination with elemental analyses. Single crystal X-ray crystallography of Bu₃Sn[O₂CC₆H₄{N=C(H)C₆H₃-2-OH(N=NC₆H₄CH₃-4)}-p] reveals a distorted tetrahedral structure which is further supported by ¹¹⁹Sn M?ssbauer data. Toxicity studies of the tributyltin(IV) complexes along with their ligands 4-[((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]benzoic acids on the second larval instar of the Anopheles stephensi mosquito larvae are also reported.     

Synthese und Reaktionen chiraler,von (R)-(−)-bzw. (S)-(+)-2-Methoxymethylpyrrolidin abgeleiteter Dithiocarbamate

Synthesis and Reactions of Chiral Dithiocarbamates Derived from (R)-(−)- or (S)-(+)-2- The synthesis, diastereoselective alkylation reactions, dithiocarboxylation, and aldol condensation of several substituted methyl (R¹ CH₂) (S)-2-(methoxymethyl)-pyrrolidine-1-dithiocarboxylates (S)- 2 and of the corresponding (R)-derivatives (R)- 2 are described. The new enantiomeric dithiocarbamates (S) -2a – e , and (R) -2a – d are obtained by reaction of (S)-(+)-[(S) -1 ] or (R)-(−)-2-(methoxymethyl)-pyrrolidine [(R) -1 ], respectively, with carbon disulfide in dry methanol/anhydrous sodium acetate and the appropriate alkylating agent. The cyclic ketene dithioacetals (S) -3 and (R) -3 are formed by dithiocarboxylation procedure of (S) -2a and (R) -2a whereas (S) -6 and (R) -6 are obtained by aldol reaction with isobutyraldehyde. (S)- 2c , d and (R) -2c , d react in a diastereoselective manner after deprotonation with n-BuLi or LiTMP/LiBr at −78°C in THF with alkyl halides to the enantiomeric compounds 4a /ent -4a, 4b /ent -4b and 5 /ent -5 , respectively.