Lanthanide(III) nitrobenzenesulfonates and p-toluenesulfonate complexes of lanthanide(III), iron(III), and copper(II) as novel catalysts for the formation of calix[4]resorcinarene

Lanthanide(III) salts of p-toluenesulfonic acid [lanthanide(III) tosylates, Ln(TOS)₃] and nitrobenzenesulfonic acid [Ln(NBSA)₃], and p-toluenesulfonate complexes of iron(III) and copper(II) were prepared, characterized, and examined as catalysts for the synthesis of resorcinol-derived calix[4]resorcinarenes. The reaction of resorcinol with benzaldehyde yields two isomers, the all-cis isomer (rccc) and the cis-trans-trans isomer (rctt) with the relative isomer ratios depending on the reaction conditions. However, in the reaction of resorcinol with octanal only one isomer, the all-cis isomer, is formed in high yields with less than 0.1 mol % of Yb(TOS)₃. Examination of lanthanide(III) tosylates and lanthanide(III) nitrobenzenesulfonates revealed that ytterbium(III) 4-nitrobenzenesulfonate [ytterbium(III) nosylate, Yb(4-NBSA)₃] and ytterbium(III) 2,4-dinitrobenzenesulfonate [Yb(2,4-NBSA)₃] are the most active catalysts. The catalysts could be easily recovered and reused several times for resorcinarene formation without loss of efficiency. Surprisingly good results were also obtained with iron(III) and copper(II) p-toluenesulfonates. Besides optimizing the reaction conditions, new insights into the reaction mechanism were also obtained.     

Preparation, Characterization and Properties of Two New Lanthanide(III)-5-(2-pyridyl)tetrazolate Complexes

Two new mononuclear lanthanide(III) complexes Ln(pytz)3(H2O)3·(H2O)3.5[Ln=Tb(1); Eu(2); Hpytz= 5-(2-pyridyl)tetrazole] were synthesized by reacting Hpytz with the corresponding lanthanide(III) ions and characterized. The single crystal X-ray diffraction analysis reveals that complexes 1 and 2 are isostructural and the lanthanide(III) ions in both complexes 1 and 2 are nine-coordinated, with three oxygen atoms of three coordination water molecules and six nitrogen atoms of three pytz ligands, forming a monocapped square antiprism. Extensive hydrogen bonds exist, resulting in a three-dimensional supramolecular network structure by hydrogen-bonds in both complexes 1 and 2, respectively. Complex 1 exhibits typical green fluorescence of Tb(III) ion and complex 2 red fluorescence of Eu(III) ion, in solid state at room temperature.     

Synthesis and Structure of a Rare Unsolvated Bis(amidinato) Lanthanide Chloride, (Piso)2CeCl (Piso = [tBuC(NAr)2]–, Ar = C6H3iPr2–2,6)

Use of the very bulky amidinate ligand [tBuC(NAr)₂]^–(= Piso, Ar = C₆H₃iPr₂–2,6) allowed the synthesis and structural characterization of the chloro‐functional complex (Piso)₂CeCl ( 1 ). Complex 1 represents a rare example of an unsolvated bis(amidinato) lanthanide chloride. An X‐ray diffraction study confirmed the presence of a pentacoordinate cerium(III) complex.     

Solvent effect on intensities off-ftransitions in lanthanide(III) complexes

A general theory of the solvent effect on the intensities of f-f; transitions of lanthanide complexes based on static and dynamic coupling between metal ion and ligands and solvent molecules is presented. New expressions are found correlating the intensity parameters with physical characteristics of the solvent. It is shown that the solvent effect influences only in the parameter ₂.     

Oxidation of 4-arylphenol trimethylsilyl ethers to p-arylquinols using hypervalent iodine(III) reagents

An efficient synthesis of p-arylquinols by the oxidation of 4-arylphenol trimethylsilyl ethers with phenyliodine(III) diacetate (PIDA) is reported. This protocol greatly improved the yield of p-quinol by minimizing oligomer side products compared to the oxidation of free phenol with hypervalent iodine(III) reagents. The innocuity of phenyliodine(III) diacetate associated with the mild conditions make the method highly competitive over metal-mediated oxidation reactions. The proposed reaction mechanism is discussed and compared to the generally accepted mechanism of 4-substituted phenols to explain the yield improvement.     

Lanthanum(III) nitrate hexahydrate or p-toluenesulfonic acid catalyzed one-pot synthesis of 4(3H)-quinazolinones under solvent-free conditions

The one-pot synthesis of quinazolinone derivatives from the reaction of anthranilic acid, trialkyl orthoformate and amines in the presence of lanthanum(III) nitrate hexahydrate or p-toluenesulfonic acid has been carried out. The reaction occurred in a few minutes under solvent-free conditions and in excellent yields.     

Self‐Assembly of Organic Chromosphere Cations with Inorganic Lanthanide(III) Complex Counterions

Hybrid complexes based on a D‐π‐A type dye p‐aminostyryl‐pyridinum cation and a lanthanide(III) complex anion were synthesized by ionic exchange reaction. Different alkyl‐substituted amino groups were used as electron donors in organic dye cations. The synthesized complexes were characterized by elemental analysis. In addition, the structural features of them were studied by single‐crystal X‐ray diffraction analysis. Their optical properties were systematically investigated by absorption and fluorescence spectroscopy.     

Zeolite-Y enslaved manganese(III) complexes as heterogeneous catalysts

Traditional catalytic procedures for oxidation of phenol produce environmentally undesirable wastes. As a consequence, there is a clear demand for development of an environmentally benign catalytic route for the selective oxidation of phenol. A series of zeolite-Y enslaved Mn(III) complexes with Schiff bases derived from vanillin furoic-2-carboxylic acid hydrazone (VFCH), vanillin thiophene-2-carboxylic acid hydrazone (VTCH), ethylvanillin thiophene-2-carboxylic acid hydrazone (EVTCH), and/or ethylvanillin furoic-2-carboxylic acid hydrazone have been synthesized and characterized by physico-chemical techniques. Catalytic oxidations of phenol using 30% H₂O₂ as an oxidant over [Mn(VTCH)₂·2H₂O]⁺-Y, [Mn(VFCH)₂·2H₂O]⁺-Y, and [Mn(EVTCH)₂·2H₂O]⁺-Y under mild conditions were studied. These zeolite-Y enslaved Mn(III) complexes are stable and recyclable under current reaction conditions.     

Bis(pyrazolyl)pyridine vanadium(III) complexes as highly active ethylene polymerization catalysts

The synthesis, characterization and catalytic activity in ethylene polymerization of novel mononuclear vanadium complexes bearing N^∧N^∧N-tridentate (pyrazolyl-pyridine) ligands are described. With AlEtCl₂ as co-catalyst, complexes 1 and 2 produce single-site catalysts that polymerized ethylene affording high density polyethylene with fairly narrow molecular weight distribution.     

Lanthanide(III) Complexes with Pyridine Head Macrocyclic Ligands

The ability of lanthanide(III) ions to form stable complexeswith three different macrocyclic ligands, L¹ , L² and L³ , has been investigated.The Schiff base macrocycle L¹ and its corresponding reduced ligand L² arederived from 2,6-bis(2-formylphenoxymethyl)pyridine and diethylentriamine;the reduced ligand L³ is derived from 2,6-diformylpyridine and N,N-bis(3-aminopropyl)methylamine. Lanthanide nitrate complexes of L¹ and L² have beenprepared by direct reaction between each ligand and the appropriate hydrated lanthanidenitrate; attempts to obtain the corresponding perchlorate complexes have been unsuccessful.All nitrate complexes of L¹ give the expected [1:1, Ln:L¹ ] stoichiometry; however, complexes obtained with L² show a [2:1, Ln:L² ] stoichiometry. Finally, complexation reactions with L³ have been carried out in order to investigatethe coordination capability of this small and flexible ligand towards the Ln(III) ions.     

Effective chemoselective deprotection of 3,4-dimethoxybenzyl (DMB) ethers in the presence of benzyl and p-methoxybenzyl (PMB) ethers by phenyliodine(III) bis(trifluoroacetate) (PIFA)

In this Letter, a selective deprotection of the alcohol protecting 3,4-dimethoxybenzyl (^3,4DMB) group is described. The hypervalent iodine(III) reagent phenyliodine bis(trifluoroacetate) (PIFA) is found to be an efficient reagent for the chemoselective deprotection of ^3,4DMB ethers in the presence of benzyl, p-methoxybenzyl, methoxymethyl, tert-butyldimethylsilyl, and tert-butyldiphenylsilyl ethers under mild conditions. This is the first example of the selective deprotection of the ^3,4DMB group from a hydroxy group with PIFA.     

Functionalized cyclopentanes via Sc(III)-catalyzed intramolecular enolate alkylation

We report herein the intramolecular α-tert-alkylation of unsaturated β-ketoesters which gives rise to highly functionalized cyclopentanes. This transformation is characterized by its operational simplicity, mild reaction conditions and the use of scandium (III) triflate as a Lewis acid catalyst. Of interest, cyclopentanes bearing heterocycles, sites for post reaction functionalization and spirocyclic architectures are accessible with this strategy.     

Catalytic activity of Mn(III) and Fe(III) complexes of meso-tetra(n-propyl)porphyrin in oxidation of olefins: Meso-alkyl substituent in comparison with the alkenyl and aryl ones

Catalytic activity of Mn(III) and Fe(III) complexes of meso-tetra(n-propyl)porphyrin, MnT(n-Pr)P(X) and FeT(n-Pr)P(X) (X = Cl, SCN, OAc) in oxidation of olefins with tetra-n-butylammonium periodate at room temperature has been studied. The influence of different parameters including the molar ratio of catalyst to imidazole, type of counter ion (X) and oxidative stability of metalloporphyrins on the efficiency of the catalysts was investigated. The results of competitive oxidation of cis- and trans-stilbene suggest the presence of a high-valent Mn-oxo as the predominant oxidant species in equilibrium with a six coordinate complex, MnT(n-Pr)P(ImH)(IO₄) in the case of MnT(n-Pr)P(OAc). An unusual preference for trans-stilbene over cis-stilbene was observed in the reaction catalyzed by FeT(n-Pr)P(OAc). Control reaction indicated a significant cis- to trans-isomerization (81%) in oxidation of cis-stilbene catalyzed by FeT(n-Pr)P(OAc) which may explain the observed unusual cis to trans-stilbene oxide ratio. While oxidation of cyclooctene and styrene led to the exclusive formation of the corresponding epoxides, oxidation of cyclohexene gave 2-cyclohexe-1-ol and cyclohexene oxide as the products. However, the results of this study clearly demonstrate the key role played by the group substituted at the meso positions of metalloporphyrins on their catalytic activity, apart from the electron-donating or electron-withdrawing properties of the substituents.     

Ru(III), Cr(III), Fe(III) complexes of Schiff base ligands bearing phenoxy Groups: Application as catalysts in the synthesis of vitamin K3

Two polydentade Schiff base ligands and their Ru(III), Cr(III) and Fe(III) complexes were synthesized and characterized by elemental analysis (C, H, N), UV/Vis, FT IR, ¹H and ¹³C NMR, LC–MS/MS, molar conductivity and magnetic susceptibility techniques. The absorption bands in the electronic spectra and magnetic moment measurements verified an octahedral environment around the metal ions in the complexes. The thermal stabilities were investigated using TGA. The synthesized complexes were used in the catalytic oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1,4-naphthoquinone; vitamin K₃, menadione, 2MNQ; using hydrogen peroxide, acetic acid and sulfuric acid. L₁-Fe(III) complex showed very efficient catalytic activity with 58.54% selectivity in the conversions of 79.11%.     

Anionic chiral cobalt(III) complexes as catalysts of asymmetric synthesis of cyanohydrins

Chiral coordinatively saturated cobalt(III) complexes with Schiff bases of enantio-pure amino acids are formed as Λ and Δ-isomers, which are not transformed into each other under normal conditions. These complexes catalyze the formation of enantiomerically enriched cyanohydrins from aldehydes and Me₃SiCN under homo-and heterogeneous catalysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 793–799, May, 2006.     

三氯化铈促进的反应及其在有机合成中的应用

综述了近年来三氯化铈促进的多种有机反应及其在有机合成中的应用, 其中重点讨论了三氯化铈促进下的碳—碳原子键、碳—杂原子键的形成反应以及多种保护基团的选择性脱保护反应等.     

Chemically modified silica gel with p-dimethylaminobenzaldehyde for selective solid-phase extraction and preconcentration of Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) by ICP-OES

Silica gel-bound amines phase modified with p-dimethylaminobenzaldehyde (p-DMABD) was prepared based on chemical immobilization technique. The product (SG-p-DMABD) was used as an adsorbent for the solid-phase extraction (SPE) Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The uptake behaviors of SG-p-DMABD for extracting these metal ions were studied using batch and column procedures. For the batch method, the optimum pH range for Cr(III) and Ni(II) extraction was ≥ 3, for Cu(II), Pb(II) and Zn(II) extraction it was ≥ 4. For simultaneous enrichment and determination of all the metals on the newly designed adsorbent, the pH value if 4.0 was selected. All the metal ions can be desorbed with 2.0 mL of 0.5 mol L^− 1 of HCl. The results indicate that SG-p-DMABD has rapid adsorption kinetics using the batch method. The adsorption capacity for these metal ions is in the range of 0.40-1.15 mmol g^− 1, with a high enrichment factor of 125. The presence of commonly coexisting ions does not affect the sorption capacities. The detection limits of the method were found to be 1.10, 0.69, 0.99, 1.10 and 6.50 μg L^− 1 for Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II), respectively. The relative standard deviation (RSD) of the method under optimum conditions was 5.0% (n = 8) for all metal ions. The method was applied to the preconcentration of Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) from the certified reference material (GBW 08301, river sediment) and water samples with satisfactory results.     

Synthesis and characterization of some lanthanide(III) chelates of some schaffer acid azo dyes

Summary A series of trivalent lanthanide chelates of the type [Ln(PHNSA) (H₂O) _n ] (2 Cl) (whereLn ³⁺=Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb or Lu;PHNSA=2-(X)-phenylazo-2-hydroxynaphthalene-6-sulphonic acid;X=H, Cl, OCH₃, CH₃ and SO₃H) have been synthesized and characterized by elemental and thermal analysis, molar conductance, IR,¹H NMR (for diamagnetic complexes), electronic spectra and magnetic susceptibility measurements. IR data along with those of the¹H NMR unequivocally proved that the coordination of the ligands to the metal ions took place in a bidentate fashion through the oxygen of the hydroxyl group and the nitrogen of the azo group. The magnetic moment values showed little deviation from Van Vleck values.

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Synthese und Charakterisierung einiger Lanthaniden(III)-Chelate von Schaffersäure-Azofarbstoffen

Zusammenfassung Es wurde eine Reihe von dreiwertigen Lanthanidenchelaten des Types [Ln(PHNSA) (H₂O) _n ] (2 Cl) (mitLn ³⁺=Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb oder Lu undPHNSA=2-(X)-Phenylazo-2-hydroxynaphthalin-6-sulphonsäure,X=H, Cl, OCH₃, CH₃ und SO₃H) synthetisiert und mittels Elementar- und thermischer Analyse, molarer Leitfähgigkeit, IR,¹H-NMR (für diamagnetische Komplexe), Elektronenspektren und Messungen der magnetischen Suszeptibilität charakterisiert. Die IR-Daten zusammen mit¹H-NMR-Befunden zeigten eindeutig, daß die Koordinierung der Liganden zum Metallion zweizähnig durch den Sauerstoff der Hydroxylgruppe und den Stickstoff der Azo-Gruppe erfolgt. Die magnetischen Momente zeigten nur eine geringe Abweichung von den Van Vleck-Werten.