1-Naphthyl- and mesityltellurium(IV, II) derivatives of small bite chelating organic ligands: Effect of steric bulk and intramolecular secondary bonding interaction on molecular geometry and supramolecular association

The synthesis and characterization of unsymmetric diorganotellurium compounds containing a sterically demanding 1-naphthyl or mesityl ligand and a small bite chelating organic ligand capable of 1,4-Te?N(O) intramolecular interaction is described. The reaction of ArTeCl₃ (Ar = 1-C₁₀H₇, Np; 2,4,6-Me₃C₆H₂, Mes) with (SB)HgCl [SB = the Schiff base, 2-(4,4′-NO₂C₆H₄CHNC₆H₃-Me)] or a methyl ketone (RCOCH₃) afforded the corresponding dichlorides (SB)ArTeCl₂ (Ar = Np, 1Aa; Mes, 1Ba) or (RCOCH₂)ArTeCl₂ (Ar = Np; R = Ph (2Aa), Me (3Aa), Np (4Aa); Ar = Mes, R = Ph (2Ba)). Reduction of 1Aa and 1Ba by Na₂S₂O₅ readily gave the tellurides (SB)ArTe (Ar = Np (1A), Mes, (1B)) but that of dichlorides derived from methylketones was complicated due to partial decomposition to tellurium powder and diarylditelluride (Ar₂Te₂), resulting in poor yields of the corresponding tellurides 2A, 2B and 3A. Oxidation of the isolated tellurides with SO₂Cl₂, Br₂ and I₂ yielded the corresponding dihalides. All the synthesized compounds have been characterized with the help of IR, ¹H, ¹³C, and ¹²⁵Te NMR and in the case of 2Aa, and 2Ba by X-ray crystallography. Appearance of only one ¹²⁵Te signal indicated that the unsymmetric derivatives were stable to disproportionation to symmetric species. Intramolecular 1,4-Te?O secondary bonding interactions (SBIs) are exhibited in the crystal structures of both the tellurium(IV) dichlorides, 2Aa, and 2Ba. Steric repulsion of the mesityl group in the latter dominates over lone pair-bond pair repulsion, resulting in significant widening of the equatorial C-Te-C angle. This appears to be responsible for the lack of Te?Cl involved supramolecular associations in the crystal structure of 2Ba.     

1—硫代—1磷杂—2，6，7—三氧杂双环[2,2,2]亲烷—4—甲撑烷氧基硫代磷酰胺的合成

以三氯硫磷、高位阻醇A等为材料，通过三步反应合成了化合物1－硫代－1磷杂－2，6，7－三氧杂双环[2,2,2]亲烷－4－甲撑烷氧基硫代磷酰胺。研究了化合物的^31P NMR和MSo产物的结构经元素分析和核磁共振等证实。     

Some Zirconium(IV) Complexes of Sterically Constrained Sulfur-Containing Schiff Bases of Heterocyclic β -Diketones: Synthetic Strategy and Structural Investigation Based Upon Spectroscopic Studies

Zirconium(IV) Schiff base chelates having the general formula ZrL(OPr ⁱ )₂ [where LH ₂ = R CH ₃ , R = –C ₆ H ₅ , –C ₆ H ₄ Cl(p)] were synthesized by the reaction of Zr(OPr ⁱ )₄.Pr ⁱ OH with sterically constrained sulfur-containing Schiff bases of heterocyclic β -diketones in a 1:1 molar ratio in dry refluxing benzene. The complexes ZrL(OPr ⁱ ) ₂ were used as important precursors for the synthesis of the complexes of the type Zr(L) ₂ . The complexes, Zr(L) ₂ , were prepared by the interaction of precursor ZrL(OPr ⁱ ) ₂ with sterically constrained sulfur-containing Schiff bases of heterocyclic β -diketones in a 1:1 molar ratio in dry benzene. The structures of these zirconium(IV) chelates have been discerned with the help of elemental analyses, physicochemical studies, and spectral [IR and NMR ( ¹ H and ¹³ C)] data. A distorted trigonal bipyramidal and a distorted octahedral geometry may be assigned to zirconium(IV) chelates of the types ZrL(OPr ⁱ ) ₂ and Zr(L) ₂ , respectively.     

Catalytic Activity of Polymer Anchored Cu-tren Complex in the Oxidation of 2,6-Di-t-butyl Phenol

Poly(styrene-co-dimethylaminoethyl methacrylate) and poly(methyl methacrylate-co- dimethylaminoethyl methacrylate) were prepared by solution polymerization. These polymers were quaternized by methyl iodide and n-hexyl bromide. The produced polymers were used as support in the aqueous oxidation of 2,6-di-tert-butylphenol (DBP) using hydrogen peroxide catalyzed by tris(2-aminoethyl)amine copper(II) complex “Cu(II)-tren complex” anchored on the prepared polymers. The products obtained from the reactions were 3,3′-5,5′-tetra-tert-butyldiphenoquinine (DPQ) and 2,6-di-tert-butyl-p-benzoquinone (BQ). No reaction products were obtained when the reaction was carried out in the absence of polymeric catalyst. The polymer composition and reaction medium greatly affect product distribution of the reaction. Polar organic solvent like DMF and methanol favor the formation of DPQ, while nonploar organic solvent like benzene and methylene chloride favor the formation of BQ. Hydrophobic branches of polymers 6 (PS-HexBr-Cu-TREN) and 8 (PMMA-HexBr-Cu-TREN) favor BQ formation as the weight of support increased. On the other hand, DPQ is favored in the presence of hydrophilic branches as observed for both polymeric catalysts 5 (PS-MeI-Cu-TREN) and 7 (PMMA-MeI-Cu-TREN).     

Design and Synthesis of Olefin Copolymers with Tunable Amounts of Comonomers Bearing Stabilizing Functionalities

The aim of this work is to search for innovative solutions to avoid physical migration of the stabilizers from plastic films. New families of macromolecular additives bearing tuned amounts of a selected functionality were explored, in particular, novel random copolymers of ethylene with 1‐olefin co‐units bearing an efficient antioxidant and/or anti‐UV moiety covalently bonded to a mono‐ or disubstituted olefinic bond. Polyolefin blends containing the novel macromolecular additives showed higher degradation temperatures with respect to the neat matrix and its blends with 2,6‐t‐butyl‐4‐methoxyphenol (BHA). Aging tests showed that the novel antioxidants also constitute a protection against photo‐oxidation.

     

CO2 Absorption Mechanism by the Nonaqueous Solvent Consisting of Hindered Amine 2-[(1,1-dimethylethyl)amino]ethanol and Ethylene Glycol

In this work, we studied the CO₂ absorption mechanism by nonaqueous solvent comprising hindered amine 2-[(1,1-dimethylethyl)amino]ethanol (TBAE) and ethylene glycol (EG). The NMR and FTIR results indicated that CO₂ reacted with an -OH group of EG rather than the -OH of TBAE by producing hydroxyethyl carbonate species. A possible reaction pathway was suggested, which involves two steps. In the first step, the acid–base reaction between TBAE and EG generated the anion HO-CH₂-CH₂-O-; in the second step, the O⁻ of HO-CH₂-CH₂-O⁻ attacked the C atom of CO₂, forming carbonate species.     

Thermal Decomposition of Spatially Hindered Phenols Using Chromatomass-spectrometric System

The present paper deals with thermal decomposition of some spatially hindered phenols, which are in the industry as stabilizers in synthetic materials used. The investigated stabilizers are separated to two groups in respect to mechanism of decomposition (group I and II). This assumption was confirmed by chromatomass-spectrometric investigations. It allows a stabilizer for forming a plastic with variety properties to choose. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reversible addition fragmentation chain transfer polymerization of sterically hindered monomers: Toward well‐defined rod/coil architectures

The sterically hindered monomers dibutyl itaconate (DBI) and dicyclohexyl itaconate (DCHI) were polymerized via reversible addition fragmentation chain transfer (RAFT) free‐radical polymerization. S,S′‐Bis(α,α′‐dimethyl‐α″‐acetic acid) trithiocarbonate, cumyl dithiobenzoate, and cumyl phenyldithioacetate have been used as RAFT agents to mediate a series of polymerizations at 65 °C yielding rod polymers ranging in number average molecular weight from 9000 to 92,000 g mol^?1. The progress of the polymerization was followed via online Fourier transform–near infrared spectroscopy. The polydispersity indices of the obtained rod polymers were relatively high at 1.4–1.7. The RAFT polymerizations of the hindered monomers used in the present study displayed both ideal living and hybrid behavior between conventional and living polymerization, depending on the RAFT agent used. DCHI rod polymers generated via the RAFT process were subsequently reinitiated in the presence of styrene to produce a range of BAAB and A‐B rod‐coil block copolymers of molecular weights up to 164,000 g mol^?1. The chain extension yields molecular weight distributions that progressively shift to higher molecular weights and are unimodal. Thermogravimetric analysis of the pDCHI‐block‐pStyrene copolymers indicates thermal degradation in two separate steps for the pDCHI and pStyrene blocks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2432–2443, 2004     

Proton Nuclear Magnetic Resonance Spectroscopy: Significant Barriers to Rotation About N-N Bonds in 3-Acylaminoquinazolin-4(3H)-One Derivatives

Abstract

The proton NMR spectra of several 3-acylaminoquinazolin-4(3H)-one derivatives have been studied as a function of temperature. The changes, which were found to occur in the spectra at high temperatures, are discussed in terms of hindered rotation about the nitrogen-nitrogen bond. The free energies of activation for the rate-determining stereochemical process were calculated to be as high as (14.7～20.6 Kcal mol^?1) for hydrazine derivatives.