Stabilization of a Chiral Dirhodium Carbene by Encapsulation and a Discussion of the Stereochemical Implications

For the first time, the stereochemical course of an asymmetric cyclopropanation can be discussed on the basis of experimental structural information on a pertinent chiral dirhodium carbene intermediate. Key to success was the formation of racemic single crystals of a heterochiral [Rh₂{(S*)‐PTTL}₄{=C(Ar)COOMe}][Rh₂{(R*)‐PTTL}₄] (Ar=MeOC₆H₄; PTTL=N‐phthaloyl‐tert‐leucinate) capsule, which has been characterized by X‐ray diffraction. NMR spectroscopic data confirm that the obtained structural portrait is also relevant in solution and provide additional information about the dynamics of this species. The chiral binding pocket is primarily defined by the conformational preferences of the N‐phthaloyl‐protected amino acid ligands and reinforced by a network of weak interligand interactions that get stronger when chlorinated phthalimide residues are used.     

Strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate

Comparison of the structures of strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine, C₂₁H₂₃N₂O₂⁺·C₁₁H₈NO₄⁻·C₁₁H₉NO₄, and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate, C₂₃H₂₇N₂O₄⁺·C₁₁H₈NO₄⁻·5.67H₂O, reveals that, unlike strychninium cations, brucinium cations display a tendency to produce stacking inter­actions with cocrystallizing guests.     

C,N‐chelated organotin(IV) compounds as catalysts for transesterification and derivatization of dialkyl carbonates

The potential catalytic activity of selected C,N‐chelated organotin(IV) compounds (e.g. halides and trifluoroacetates) for derivatization of both dimethyl carbonate (DMC) and diethyl carbonate (DEC) was investigated. Some tri‐, di‐ and monoorganotin(IV) species (L^CN(n‐Bu)₂SnCl (1), L^CN(n‐Bu)₂SnCl.HCl (1a), L^CN(n‐Bu)₂SnI (2), L^CNPh₂SnCl (3), L^CNPh₂SnI (4), L^CN(n‐Bu)SnCl₂ (5), L^CNSnBr₃ (6) and [L^CNSn(OC(O)CF₃)]₂(μ‐O)(μ‐OC(O)CF₃)₂ (7)) bearing the L^CN moiety (L^CN = 2‐(N,N‐dimethylaminomethyl)phenyl‐) were assessed as catalysts for reactions of both DMC and DEC with various substituted anilines. The catalytic activities of 4 and 7 for derivatization of DMC with p‐substituted phenols were studied for comparison with the standard base K₂CO₃/Silcarbon K835 catalyst (catalyst 8). The composition of resulting reaction mixtures was monitored by multinuclear NMR spectroscopy, GC and GC‐MS techniques. In general, catalysts 1, 3 and 7 exhibited the highest catalytic activity for all reactions studied, while some of them yielded selectively carbonates, carbamates, lactam or substituted urea. Copyright © 2012 John Wiley & Sons, Ltd.     

Syntheses and crystal structures of diorganotin(IV) bis(2‐pyridinethiolato‐N‐oxide) complexes

The complexes di‐n‐butyldi(2‐pyridinethiolato‐N‐oxide)tin(IV) (1), diphenyldi(2‐pyridinethiolato‐N‐oxide)tin(IV) ( 2 ) and dibenzyldi(2‐pyridinethiolato‐N‐oxide)tin(IV) ( 3 ) are synthesized and characterized by elemental analyses, IR, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopy, and their structures are determined by X‐ray crystallography. In complex 1 the coordination geometry at tin is a skew‐trapezoidal bipyramid, with cis‐S,S and cis‐O,O atoms occupying the trapezoidal plane and two n‐butyl groups occupying the apical positions, which also exhibits strong π–π stacking interactions. In complexes 2 and 3 the geometry at tin is distorted cis‐octahedral, with cis‐O,O and cis‐C,C atoms occupying the equatorial plane and trans‐S,S atoms occupying the apical positions. Their in vitro cytotoxicity against two human tumour cell lines, MCF‐7 and WiDr is reported. The ID₅₀ values found are comparable to those found for cis‐platin, but lower than for many other diorganotin compounds. Copyright © 2003 John Wiley & Sons, Ltd.     

New Bis‐o‐Benzoquinoid Ligands with Ethylene Bridge and Their Metal Complexes

The treatment of di‐o‐quinone 4,4′‐(ethane‐1,2‐diyl)‐bis(3,6‐di‐tert‐butyl‐o‐benzoquinone) (Q–CH₂–CH₂–Q, 1 ) leads to its rearrangement to form di‐p‐quinomethide 4,4′‐(ethane‐1,2‐diylidene)bis(2‐hydroxy‐3,6‐di‐tert‐butyl‐cyclohexa‐2,5‐dienone) ( 2 ). The subsequent oxidation of 2 by an alkaline solution of K₃[Fe(CN)₆] yielded the new di‐o‐quinone 4,4′‐(ethene‐1,2‐diyl)bis(3,6‐di‐tert‐butyl‐o‐benzoquinone) (Q–CH=CH–Q, 3 ), which contains an ethylene bridge. The formation of mono‐ and poly‐reduced derivatives of 2 and 3 with potassium, thallium was studied by EPR technique. The dinuclear thallium derivative of 3 , Tl(SQ–CH=CH–SQ)Tl, was found to exist in the diamagnetic quinomethide form. The most stable derivatives of 2 and 3 are triphenyltin(IV) bis‐p‐quinomethide‐phenolate ( 4 ) and triphenylantimony(V) bis‐catecholate ( 5 ), which have been synthesized and isolated. The molecular structures of 2 , 3 , and 5 were characterized by single‐crystal X‐ray diffraction.     

Copper(II) Complexes of ω‐Hydroxy‐Functionalized N‐Salicylidenehydrazides show pH‐Controlled Switching between Dicationic Dimers and Neutral One‐Dimensional Coordination Polymers

New copper(II) complexes of the hydrazone ligands H₂salhyhb, H₂salhyhp, and H₂salhyhh, derived from salicylaldehyde and ω‐hydroxy carbonic acid hydrazides, have been synthesized and physically characterized. Two fundamental structures were found in solid state depending on the pH‐value of the reaction solution. Acidic conditions lead to the formation of the di‐μ‐phenoxo‐bridged dicationic complex dimers [{Cu(Hsalhyhb)}₂]²⁺ ( 1a ), [{Cu(Hsalhyhp)}₂]²⁺ ( 2a ), and [{Cu(Hsalhyhh)}₂]²⁺ ( 3a ), isolated as perchlorate salts. The dimeric complexes show strong antiferromagnetic coupling with J = ?399 ( 1a ), ?410 ( 2a ), and ?311 cm^?1 ( 3a ). Higher pH‐values resulted in the aggregation of neutral copper ligand fragments to the one‐dimensional coordination polymers [{Cu(salhyhb)}_n] ( 1b ), [{Cu(salhyhp)}_n] ( 2b ), and [{Cu(salhyhh)}_n] ( 3b ). 3b has been examined by means of X‐ray crystallography and represents the first example of a structurally characterized neutral copper(II) N‐salicylidenehydrazide complex without additional ligands. The magnetic interactions in the polymers are also antiferromagnetic with J = ?125 ( 1b ), ?136 ( 2b ), and ?148 cm^?1 ( 3b ), but strongly reduced compared to the corresponding dimeric complexes. The two basic structure types can be reversibly interconverted simply by pH‐control.     

Organophosphine/phosphite‐stabilized silver(I) complexes bearing N‐hydroxysuccinimide ligand: synthesis,solid state structure and their potential use as MOCVD precursors

Six organophosphine/phosphite‐stabilized silver(I) N‐hydroxysuccinimide complexes of type [C₄H₄NO₃Ag?L_n] (L = PPh₃; n = 1, 2a; n = 2, 2b; L = P(OEt)₃; n = 1, 2c; n = 2, 2 d; L = P(OMe)₃; n = 1, 2e; n = 2, 2f) were prepared. These complexes were obtained in high yields and characterized by elemental analysis, ¹H NMR, ¹³ C{¹H} NMR and IR spectroscopy, respectively. The molecular structure of 2b has been determined by X‐ray single‐crystal analysis in which the silver atom is in a distorted tetrahedral geometry. An interstitial methanol solvent molecule is hydrogen bonded to the oxygen atom of N‐hydroxysuccinimide molecule. Complex 2f was used to deposit silver films by metal‐organic chemical vapor deposition (MOCVD) for the first time. The silver film obtained at 480 °C is dense and homogeneous, which is composed of many well‐isolated, granular particulates spreading all over the substrate surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Zinc (II), palladium (II) and cadmium (II) complexes containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline derivatives: Synthesis,characterization and methyl methacrylate polymerization

A series of Zn (II), Pd (II) and Cd (II) complexes, [(L) _n MX ₂ ] _m (L = L‐a–L‐c; M = Zn, Pd; X = Cl; M = Cd; X = Br; n, m = 1 or 2), containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline ( L‐a ), 4‐methoxy‐N‐(pyridin‐2‐ylmethyl) aniline ( L‐b ) and 4‐methoxy‐N‐methyl‐N‐(pyridin‐2‐ylmethyl) aniline ( L‐c ) have been synthesized and characterized. The X‐ray crystal structures of Pd (II) complexes [L ₁ PdCl ₂ ] (L = L‐b and L‐c) revealed distorted square planar geometries obtained via coordinative interaction of the nitrogen atoms of pyridine and amine moieties and two chloro ligands. The geometry around Zn (II) center in [(L‐a)ZnCl ₂ ] and [(L‐c)ZnCl ₂ ] can be best described as distorted tetrahedral, whereas [(L‐b) ₂ ZnCl ₂ ] and [(L‐b) ₂ CdBr ₂ ] achieved 6‐coordinated octahedral geometries around Zn and Cd centers through 2‐equivalent ligands, respectively. In addition, a dimeric [(L‐c)Cd(μ ‐ Br)Br] ₂ complex exhibited typical 5‐coordinated trigonal bipyramidal geometry around Cd center. The polymerization of methyl methacrylate in the presence of modified methylaluminoxane was evaluated by all the synthesized complexes at 60°C. Among these complexes, [(L‐b)PdCl ₂ ] showed the highest catalytic activity [3.80 × 10⁴ g poly (methyl methacrylate) (PMMA)/mol Pd hr^?1], yielding high molecular weight (9.12 × 10⁵ g mol^?1) PMMA. Syndio‐enriched PMMA (characterized using ¹H‐NMR spectroscopy) of about 0.68 was obtained with T_g in the range 120–128°C. Unlike imine and amine moieties, the introduction of N‐methyl moiety has an adverse effect on the catalytic activity, but the syndiotacticity remained unaffected.     

Determination of N‐nitrosamines by automated dispersive liquid–liquid microextraction integrated with gas chromatography and mass spectrometry

An automated dispersive liquid–liquid microextraction integrated with gas chromatography and mass spectrometric procedure was developed for the determination of three N‐nitrosamines (N‐nitroso‐di‐n‐propylamine, N‐nitrosopiperidine, and N‐nitroso di‐n‐butylamine) in water samples. Response surface methodology was employed to optimize relevant extraction parameters including extraction time, dispersive solvent volume, water sample pH, sodium chloride concentration, and agitation (stirring) speed. The optimal dispersive liquid–liquid microextraction conditions were 28 min of extraction time, 33 μL of methanol as dispersive solvent, 722 rotations per minute of agitation speed, 23% w/v sodium chloride concentration, and pH of 10.5. Under these conditions, good linearity for the analytes in the range from 0.1 to 100 μg/L with coefficients of determination (r²) from 0.988 to 0.998 were obtained. The limits of detection based on a signal‐to‐noise ratio of 3 were between 5.7 and 124 ng/L with corresponding relative standard deviations from 3.4 to 5.9% (n = 4). The relative recoveries of N‐nitroso‐di‐n‐propylamine, N‐nitrosopiperidine, and N‐nitroso di‐n‐butylamine from spiked groundwater and tap water samples at concentrations of 2 μg/L of each analyte (mean ± standard deviation, n = 3) were (93.9 ± 8.7), (90.6 ± 10.7), and (103.7 ± 8.0)%, respectively. The method was applied to determine the N‐nitrosamines in water samples of different complexities, such as tap water, and groundwater, before and after treatment, in a local water treatment plant.     

稀土与N-对甲苯磺酰甘氨酸配合物的合成、晶体结构与性质

Complexes { [Ln（H20）2（TsGlyH）a]m·nH2O}∞ （Ln=La （1）, m=2, n=6; Nd （2）, m=2, n=7; Eu （3）, m=2, n= 0; Gd （4）, m=2, n=2; Er （5）, m=3, n=5 and Yb （6）, m=3, n=0, TsGlyH=N-p-tosylglycine monoanion）, have been prepared and characterized by IR spectra, elemental analysis, and TG-DTG 4 and 5 were structurally determined by X-ray diffraction analysis, showing that both of them are comprised of a one dimensional chain structure established via the coordination of μ-carboxylate groups from N-p-tosylglycinate to the corresponding lanthanide（Ⅲ） ions. The one dimensional chains were found inclined to form two-dimensional network via hydrogen bonding and then three dimensional network structure via non-classical hydrogen bonding. The fluorescence spectra of them revealed that the fluorescence of the ligand was quenched by Ln（Ⅲ） ions. In the tested biological activity experiments, they behaved inhibiting effects against the growth of bacteria, indicating that it is a potential medicament worthy of further investigation.     

The Features of Interaction of Bis(4, 6‐di‐tert‐butyl‐N‐(2, 6‐diisopropylphenyl)‐o‐amidophenolato)tin(IV) with Bromine and Iodine

The oxidation of tin(IV) bis‐amidophenolate (APiPr)₂Sn · THF ( I ) by bromine and iodine leads to the formation of monoradical mixed‐ligand complexes (APiPr)(ISQiPr)SnBr · THF ( II ) and (APiPr)(ISQiPr)SnI · THF ( III ) or diradical complexes (ISQiPr)₂SnBr₂ ( IV ) and (ISQiPr)₂SnI₂ ( V ), respectively [APiPr = dianion 4, 6‐di‐tert‐butyl‐N‐(2, 6‐diisopropylphenyl)‐o‐amidophenolate; ISQiPr = radical‐anion 4, 6‐di‐tert‐butyl‐N‐(2, 6‐diisopropylphenyl)‐o‐iminobenzosemiquinone], depending on the molar ratio of reagents (2:1 or 1:1). According to EPR data for compounds II and III , the unpaired electron is delocalized between both organic ligands. The EPR spectrum of IV in toluene matrix at 130 K is typical for diradical species with S = 1 with parameters D = 530 G, E = 105 G. The mixed‐ligand complexes II and III are unstable and undergo to symmetrization leading to formation of IV or V . The molecular structures of IV and V are determined by X‐ray analysis.     

Organophosphine/phosphite‐stabilized silver(I) complexes bearing N‐acetylbenzamide ligand: synthesis,characterization and potential application in metal organic chemical vapor deposition

New N‐silver(I) acetylbenzamide complexes of type L_n?AgNC₉H₈O₂ (L = PPh₃; n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)₃; n = 1, 2d; n = 2, 2e; n = 3, 2f) were prepared. These complexes were obtained in high yields and characterized by elemental analysis, ¹H NMR, ¹³C{H} NMR, ³¹P{H} NMR and IR spectroscopy, respectively. The molecular structure of 2b has been determined by X‐ray single‐crystal analysis in which the silver atom is in a distorted tetrahedral geometry and crystallizes as cis–trans. New N‐silver(I) acetylbenzamide complexes have a four‐membered ring, which could influence their chemical and physical properties and modulate volatility. Metal organic chemical vapor deposition experiments were carried out successfully at 400°C and 450°C using 2e as precursor for the deposition of silver films, respectively. The high‐purity silver film obtained at 400°C is dense and homogeneous. Copyright © 2012 John Wiley & Sons, Ltd.     

Donor property of cobalt(II) Schiff base complexes toward triphenyltin(IV)‐chloride: A kinetic study

In this study, some cobalt(II)tetraaza Schiff base complexes were used as donors in coordinating to triphenyltin(IV)chloride as acceptors; the kinetics and mechanism of the adduct formation were studied spectrophotometrically. Co(II)tetraaza Schiff base complexes used were [Co(amaen)][N,N′‐ethylene‐bis‐(o‐amino‐α‐methylbenzylideneiminato)cobalt(II)] ( 1 ), [Co(appn)] [N,N′‐1,2‐propylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 2 ), [Co(ampen)] [N,N′‐ethylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt‐(II)] ( 3 ), [Co(cappn)][N,N′‐1,2‐proylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 4 ), and [Co(campen)] [N,N′‐ethylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylid‐eneiminato)cobalt(II)] ( 5 ). The reactivity trend of the complexes in interaction with triphenyltin(IV)chloride was Co(amaen) > Co(appn) > Co(ampen) > Co(cappn) > Co(campen). The linear plots of k_obs versus the molar concentration of the triphenyltin(IV)chloride, a high span of the second‐order rate constant k₂ values, and large negative values of ΔS^≠ and low ΔH^≠ values suggest an associative (A) mechanism for the acceptor–donor adduct formation. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 635–640, 2012     

Antioxidative vs cytotoxic activities of organotin complexes bearing 2,6‐di‐tert‐butylphenol moieties

Two series of organotin(IV) complexes with Sn–S bonds on the base of 2,6‐di‐tert‐butyl‐4‐mercaptophenol ( L ¹ SH ) of formulae Me₂Sn(L¹S)₂ ( 1 ); Et₂Sn(L¹S)₂ ( 2 ); Bu₂Sn(L¹S)₂ ( 3 ); Ph ₂ Sn(L¹S)₂ ( 4 ); (L¹)₂Sn(L¹S)₂ ( 5 ); Me₃Sn(L¹S) ( 6 ); Ph₃Sn(L¹S) ( 7 ) (L¹ = 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl), together with the new ones [Me₃SnCl(L²)] ( 8 ), [Me₂SnCl₂(L²)₂] ( 9 ) ( L ²  = 2‐(N‐3′,5′‐di‐tert‐butyl‐4′‐hydroxyphenyl)‐iminomethylphenol) were used to study their antioxidant and cytotoxic activity. Novel complexes 8 , 9 of Me_nSnCl_4 ? n (n = 3, 2) with Schiff base were synthesized and characterized by ¹H, ¹³C NMR, IR and elemental analysis. The crystal structures of compounds 8 and 9 were determined by X‐ray diffraction analysis. The distorted tetrahedral geometry around the Sn center in the monocrystals of 8 was revealed, the Schiff base is coordinated to the tin(IV) atom by electrostatic interaction and formation of short contact Sn–O 2.805 Å. In the case of complex 9 the distorted octahedron coordination of Sn atom is formed. The antioxidant activity of compounds as radical scavengers and reducing agents was proved spectrophotometrically in tests with stable radical DPPH, reduction of Cu²⁺ (CUPRAC method) and interaction with superoxide radical‐anion. Moreover, compounds have been screened for in vitro cytotoxicity on eight human cancer cell lines. A high activity against all cell lines with IC₅₀ values 60–160 nM was determined for the triphenyltin complex 7 , while the introduction of Schiff base decreased the cytotoxicity of the complexes. The influence on mitochondrial potential and mitochondrial permeability for the compounds 8 and 9 has been studied. It is shown that studied complexes depolarize the mitochondria but don't influence the calcium‐induced mitochondrial permeability transition.     

Polymerization of n‐phenyl maleimide by lanthanide complexes

N‐Phenyl maleimide (N‐PMI) was successfully polymerized by divalent rare‐earth complexes (ArO)₂Sm(THF)₄ (ArO = 2,6‐di‐tert‐butyl‐4‐methyl phenoxo‐; THF = tetrahydrofuran) and (Ar′O)₂Ln(THF)₃ (Ar′O = 2,6‐di‐tert‐butyl phenoxo‐; Ln = Sm, Yb, or Eu). The central metals greatly affected the reactivity, and the reactivity order was Sm(II) > Yb(II) > Eu(II). The activity of (Ar′O)₂Sm(THF)₃ was higher than that of (ArO)₂Sm(THF)₄. The polymerization yields were higher in THF than in other solvents, and the maximum yields were obtained around 25 °C. A proposed mechanism is discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3966–3972, 2005     

Coordination behaviour of the 2‐(N,N‐dimethylaminomethyl)phenyl ligand towards the di‐t‐butylchlorotin(IV) moiety

{2‐(N,N‐Dimethylaminomethyl)phenyl}(di‐t‐butyl)tin(IV)chloride, {2‐[(CH₃)₂NCH₂]C₆H₄}Sn(t‐Bu)₂ Cl, has been prepared and characterized using NMR and crystallography. This is the first example of a triorganotin(IV) halide containing the 2‐[(CH₃)₂NCH₂]C₆H₄—group as a C,N‐chelating ligand with a weak intramolecular Sn—N interaction because of the steric hindrance of t‐butyl groups. The interatomic Sn—N distance is elongated to 2.904(14) Å and the central tin atom is distorted trigonal bipyramidal. Copyright © 2004 John Wiley & Sons, Ltd.     

N‐Methylimidazolkomplexe des Berylliums: [Be(Me‐Im)4]I2 und [Be3(μ‐OH)3(Me‐Im)6]Cl3

Tetra(N‐methylimidazole)‐beryllium‐di‐iodide, [Be(Me‐Im)₄]I₂ ( 1 ), was prepared from beryllium powder and iodine in N‐methylimidazole suspension to give yellow single crystal plates, which were characterized by X‐ray diffraction and IR spectroscopy. Compound 1 crystallizes tetragonally in the space group I 2d with four formula units per unit cell. Lattice dimensions at 100(2) K: a = b = 1784.9(1), c = 696.2(1) pm, R₁ = 0.0238. The structure consists of homoleptic dications [Be(Me‐Im)₄]²⁺ with short Be–N distances of 170.3(3) pm and iodide ions with weak interionic C–H ··· I contacts. Experiments to yield crystalline products from reactions of N‐methylimidazole with BeCl₂ and (Ph₄P)₂[Be₂Cl₆], respectively, in dichloromethane solutions were unsuccessful. However, single crystals of [Be₃(μ‐OH)₃(Me‐Im)₆]Cl₃ ( 2 ) were obtained from these solutions in the presence of moisture air. According to X‐ray diffraction studies, two different crystal individuals ( 2a and 2b ) result, depending on the starting materials BeCl₂ and (Ph₄P)₂[Be₂Cl₆], respectively [ 2a : Space group P2₁/n, Z = 4; 2b : Space group P , Z = 2]. As a side‐product from the reaction of N‐methylimidazole with (Ph₄P)₂[Be₂Cl₆] single crystals of (Ph₄P)Cl·CH₂Cl₂ ( 3 ) were identified crystallographically (P2₁/n, Z = 4) which are isotypical with the corresponding known bromide (Ph₄P)Br·CH₂Cl₂.     

Potassium enolates of N,N‐dialkylamides as initiators of anionic polymerization

Stable potassium enolates of N,N‐diethylacetamide [α‐potassio‐N,N‐diethylacetamide ( 1 )], N,N‐diethylpropionamide [α‐potassio‐N,N‐diethylpropionamide ( 2 )], and N,N‐diethylisobutyramide [α‐potassio‐N,N‐diethylisobutyramide ( 3 )] were prepared by the proton abstraction of the corresponding N,N‐diethylamides with diphenylmethylpotassium (Ph₂CHK) or potassium naphthalenide in THF. The relative nucleophilicity of 1 – 3 was estimated to be in the order of 1 < 3 < 2 from the results of the alkylation reaction with methyl iodide. N,N‐diethylacetamide transferred its α‐proton to 2 quantitatively in THF at 0 °C, whereas no reaction occurred between N,N‐diethylisobutyramide and 2 ; this indicated the relative basicity to be 1 < 2 ～ 3 . Anionic polymerizations of N,N‐diethylacrylamide (DEA) and methyl methacrylate were quantitatively initiated with 2 in THF at ?78 °C, whereas the initiation efficiencies of 2 for styrene and 2‐vinylpyridine were about 2 and 67%, respectively. The initiation of DEA with 1 – 3 at ?78 or 0 °C in THF gave poly (DEA)s having broad molecular weight distributions (MWDs; M_w/M_n = 2) and ill‐controlled molecular weights. In contrast, poly(DEA)s of narrow MWDs (M_w/M_n < 1.2) and predicted M_n's were obtained with 2 in the presence of diethylzinc (Et₂Zn) at ?78 °C, whereas the initiations with 1 /Et₂Zn and 3 /Et₂Zn at ?78 °C resulted in poor control of the molecular weights. At the higher temperature of 0 °C, all the binary initiator systems ( 1 – 3 /Et₂Zn) induced controlled polymerizations of DEA in terms of the conversion, molecular weight, and MWD. The poly(DEA)s produced with 1 – 3 /Et₂Zn at 0 °C showed mr‐rich configurations (mr = 76–89%), as observed for the poly(DEA) generated with Ph₂CHK/Et₂Zn. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1260–1271, 2007     

Bismuth(III) Complexes with N,N‐Di(2‐hydroxylethyl)aminodithiocarboxylate: Synthesis and Crystal Structure of {Bi[S2CN(C2H4OH)2]2[1, 10‐Phen]2(NO3)}·3H2O and (Bi[S2CN(C2H4OH)2]3}2

Two novel one‐ and two‐dimensional network structure bismuth(III) complexes with N, N‐di(2‐hydroxylethyl)‐aminodithiocarboxylate, {Bi[S₂CN(C₂H₄OH)₂]₂[1, 10‐Phen]₂(NO₃)}·3H₂O (1) and (Bi[S₂CN(C₂H₄OH)₂]₃)₂ (2) were synthesized. Their crystal and molecular structures were determined by X‐ray single crystal diffraction analysis. The crystal 1 belongs to monoclinic system with space group C2/c, a=1.6431(7) nm, b=2.4323(10) nm, c= 1.2646(5) nm, β=126. 237(5), Z=4, V=4.076(3) nm³, D_c=1.757 Mg/m^3, μ=4.598 mm^?1, F(000)=2156, R= 0.0211, wR=0.0369. The structure shows a distorted square antiprism configuration with eight‐coordination for the central Bi atom. The one‐dimensional chain structure was formed by H‐bonding interaction between hydroxyl group of N, N‐di(2‐hydroxylethyl)aminodithiocarboxylate ligands and crystal water. The crystal 2 belongs to monoclinic system with space group p2(1)/c, a= 1.1149(4) nm, b=2.1274(8) nrn, c=2.2107(8) nm, β=98.325(8)°, 2=4, V=5. 188(3) nm³, Dc=1.920 Mg/m³, μ=7.315 mm^?1, F(000)=2944, R=0.0565, wR=0.0772. The structure shows a distorted square antiprism configuration with eight‐coordination for the central Bi atoms. The two‐dimensional network structure was formed by H‐bonding interaction between adjacent molecules.     

How the Substitution Faraway from NHCs Affects the Structural Features and Catalytic Activity of Dicarbene Dipalladium Complexes

A series of [PdPyCl₂]₂(di‐NHC) complexes were prepared (di‐NHC are two 1‐(2,6‐dimethylphenyl)imidazolidene molecules bridged by an aliphatic –(CH₂)_n– linker (n = 3, 4, 5, 6, and 10)). All complexes were fully characterized by NMR spectroscopy and elemental analyses. The crystal structures of four complexes (n = 3, 4, 5 and 6) were determined by X‐ray diffraction. The influence of the distant methyl group on the structural features and catalytic activity with increasing of length of linker was investigated by comparing the results of these 2,6‐dimethylphenyl palladium complexes with those of their known mesityl analogues. X‐ray studies show the distant methyl substitution has big impact on the structure feature of the complexes with the shorter linker between two NHC (ethylene and propylene), but has a little or no effect on that of the complexes with longer linker (butylene and hexylene). Catalytic results of the arylation of styrene show that the remote substitute has big effect on the regioselectivity of the product in all complexes with shorter and longer linkers, but has a limited effect on the yield.