Syntheses and Structures of Nitridorhenium(V) and Nitridotechnetium(V) Complexes with N,N‐[(Dialkylamino)(thiocarbonyl)]‐N′‐(2‐hydroxyphenyl)benzamidines

[MNCl₂(PPh₃)₂] complexes (M = Re, Tc) react with N‐[(dialkylamino)(thiocarbonyl)]‐N′‐(2‐hydroxyphenyl)benzamidines (H₂L¹) with formation of neutral, five‐coordinate nitrido complexes of the composition [MN(L¹)(PPh₃)]. The products have distorted square‐pyramidal coordination spheres with each a tridentate, double‐deprotonated benzamidine and a PPh₃ ligand in their basal planes.     

Polymeric dopant effects of bent‐core covalent‐bonded and hydrogen‐bonded structures on banana‐shaped liquid crystalline complexes

Two series of banana‐shaped liquid crystalline (LC) H‐bonded complexes HP_m / CB_n (i.e., bent‐core H‐bonded side‐chain homopolymer HP mixed with bent‐core covalent‐bonded small molecule CB ) and CP_m / HB_n (i.e., bent‐core covalent‐bonded side‐chain homopolymer CP mixed with bent‐core H‐bonded small molecular complex HB ) with various m/n molar ratios were developed. The bent‐core covalent‐ and H‐bonded structural moieties were homopolymerized in the banana‐shaped LC H‐bonded complexes HP_m / CB_n and CP_m / HB_n , respectively. The influences of m/n molar ratios (polymeric moieties vs. small molecular moieties) on the mesomorphic and electro‐optical properties of both banana‐shaped LC H‐bonded complexes HP_m / CB_n and CP_m / HB_n were investigated. The polar smectic phases could be achieved and stabilized by smaller contents of polymeric dopants in banana‐shaped LC H‐bonded complexes, such as HP1/CB10 , HP1/CB15 , CP1/HB10 , and CP1/HB15 , which possessed tunable spontaneous polarization (Ps) values according to the molar ratios of m/n , that is, lower Ps values obtained in H‐bonded complexes HP_m /CB_n and CP_m / HB_n with higher ratios of H‐bonded moieties (larger m/n molar ratios), respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 764–774, 2010     

Determination of L‐Cystine by a New Sensitive Cucurbit[7]uril/palmatine Probe

In the presence of cucurbit[7]uril (CB[7]), the CB[7] could react with palmatine, which served as a sensitive fluorescence probe, to form host‐guest stable complexes and the fluorescence intensity of the complexes was greatly enhanced. The fluorescence intensity decreased linearly with an increasing number of L‐cystine in the inclusion system. The experimental results show that there exists a competition between L‐cystine and palmatine for the CB[7] hydrophobic cavity and L‐cystine occupies the space of CB[7] cavity, leading palmatine molecules to be forced to reside in the aqueous environment. Based on the fluorescence quenching of the CB[7]/palmatine complexes resulting from complex formation between CB[7] and L‐cystine, a spectrofluorimetric method for the determination of L‐cystine in aqueous solution in the presence of CB[7] was developed. The linear relationship between the corresponding values of the fluorescence quenching ΔF and L‐cystine concentration was obtained in the range of 6.0 to 1.5×10³ ng·mL^?1, with a correlation coefficient (r) of 0.9996. The detection limit was 2.0 ng·mL^?1. The application of the present method to the determination of L‐cystine in tablets gave satisfactory results. This paper also discussed the mechanism of the fluorescence indicator probe.     

2D l‐Di‐toluoyl‐tartaric acid Lanthanide Coordination Polymers: Toward Single‐component White‐Light and NIR Luminescent Materials

A series of five l ‐di‐p‐toluoyl‐tartaric acid (l ‐DTTA) lanthanide coordination polymers, namely {[Ln₄K⁴ L₆(H₂O)_x]?yH₂O}_n, [Ln=Dy ( 1 ), x=24, y=12; Ln=Ho ( 2 ), x=23, y=12; Ln=Er ( 3 ), x=24, y=12; Ln=Yb ( 4 ), x=24, y=11; Ln=Lu ( 5 ), x=24, y=12] have been isolated by simple reactions of H₂L (H₂L= L ‐DTTA) with LnCl₃?6 H₂O at ambient temperature. X‐ray crystallographic analysis reveals that complexes 1 – 5 feature two‐dimensional (2D) network structures in which the Ln³⁺ ions are bridged by carboxylate groups of ligands in two unique coordinated modes. Luminescent spectra demonstrate that complex 1 realizes single‐component white‐light emission, while complexes 2 – 4 exhibit a characteristic near‐infrared (NIR) luminescence in the solid state at room temperature.     

Synthesis, Spectroscopic and Electrochemical Investigations of Two vic-Dioximes and Their Mononuclear Ni（Ⅱ）, Cu（Ⅱ） and Co（Ⅱ） Metal Complexes Containing Morpholine Group

Two vic-dioxime ligands （LxH2） containing morpholine group have been synthesized from 4-[2-（dimethylaminoethyl）] morpholine with anti-phenylchloroglyoxime or anti-monochloroglyoxime in absolute THF at -15 ℃. Reaction of two vic-dioxime ligands with MCl2·nH2O （M： Ni, Cu or Co and n=2 or 6） salts in 1 ： 2 molar ratio afforded metal complexes of type [M（LxH）2] or [M（LxH）2·2H2O]. All of metal complexes are non-electrolytes as shown by their molar conductivities （Am） in DMF （dimethyl formamide） at 10^-3 mol·L^-1. Structures of the ligands and metal complexes have been solved by elemental analyses, FT-IR, UV-Vis, ^1H NMR and ^13C NMR, magnetic susceptibility measurements, molar conductivity measurements. Furthermore, redox properties of the metal complexes were investigated by cyclic voltammetry.     

Pyrazole Based Mono‐ and Di‐Substituted Half Sandwich d6 Platinum Group Metal Complexes: Synthesis and Spectral Characterization

Reactions of pyrazole based ligand and halide bridged arene d⁶ metal precursors resulted a series of mono and di‐substituted pyrazole based half sandwich d⁶ metal complexes. In general, they are formulated as [(arene)MLCl₂] [M = Ru, arene = benzene ( 1 ), p‐cymene ( 2 ), arene = Cp*, M = Rh ( 3 ) and Ir ( 4 )] and [(arene)ML₂Cl] [M = Ru, arene = benzene ( 5 ), p‐cymene ( 6 ), arene = Cp*, M = Rh ( 7 ) and Ir ( 8 )]. All these complexes were characterized by various spectroscopic techniques (IR, ¹H NMR, ESI‐MS, and UV/Vis). The molecular structures were confirmed by single‐crystal X‐ray diffraction technique. Spectroscopic studies revealed that complexation i.e., mono‐ and di‐substitution occurred by the ratio‐based reaction between pyrazole ligand and metal precursor through the neutral nitrogen rather than protic nitrogen. In these complexes deprotonation of the protic nitrogen does not occur unlike the other complexes containing pyrazole derivatives, in which the pyrazole ligand is anionic.     

Alkane Oxidation by an Immobilized Nickel Complex Catalyst: Structural and Reactivity Differences Induced by Surface‐Ligand Density on Mesoporous Silica

Immobilized nickel catalysts SBA*‐ L ‐x/Ni ( L =bis(2‐pyridylmethyl)(1H‐1,2,3‐triazol‐4‐ylmethyl)amine) with various ligand densities ( L content (x)=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl‐functionalized mesoporous silicas SBA‐N₃‐x. Related homogeneous ligand LtBu and its Ni^II complexes, [Ni( LtBu )(OAc)₂(H₂O)] ( LtBu /Ni) and [Ni( LtBu )₂]BF₄ (2 LtBu /Ni), have been synthesized. The L /Ni ratio (0.9–1.7:1) in SBA*‐ L ‐x/Ni suggests the formation of an inert [Ni L ₂] site on the surface at higher ligand loadings. SBA*‐ L ‐x/Ni has been applied to the catalytic oxidation of cyclohexane with m‐chloroperbenzoic acid (mCPBA). The catalyst with the lowest loading shows high activity in its initial use as the homogeneous LtBu /Ni catalyst, with some metal leaching. As the ligand loading increases, the activity and Ni leaching are suppressed. The importance of site‐density control for the development of immobilized catalysts has been demonstrated.     

Spectroscopic and electrochemical study for evaluating DNA interaction activity of 4‐(3‐halophenyl)‐6‐(pyridin‐2‐yl)pyrimidin‐2‐amine based piano stool Cp* Rh (III) and Ir (III) complexes

Six novel organometallic half sandwich complexes [(η5‐C₅Me₅)M(L^1–3)Cl]Cl.2H₂O were synthesized using [{(η⁵‐C₅Me₅)M(μ‐Cl)Cl₂], where M = Ir (III)/Rh (III) and L^1–3 = three pyridyl pyrimidine based ligands; and characterized by NMR, Infra‐red spectroscopy, conductance, elemental and thermal analysis. The complex‐DNA binding mode and/or strength evaluated using absorption titration, electrochemical studies and hydrodynamic measurement proposed intercalative binding mode, which was also confirmed by molecular docking study. Differential pulse voltammetry and cyclic voltammetry studies indicated an alteration in oxidation and reduction potentials of complexes (M⁺⁴/M⁺³) in presence of CT‐DNA. The metal complexes can cleave plasmid DNA as proposed in gel electrophoretic analysis. The LC₅₀ values of complexes evaluated on brine shrimp suggested their potent cytotoxic nature.     

Diblock copolymer–azobenzene complexes through hydrogen bonding: Self‐assembly and stable photoinduced optical anisotropy

We have demonstrated the preparation of a series of photoaddressable supramolecular block copolymers by mixing a carboxy‐terminated azobenzene derivative, 6‐[4‐(4′‐cyanophenylazo)phenyloxy]hexanoic acid (AZO), and two polystyrene‐b‐poly(4‐vinylpiridine) (PS‐b‐P4VP) block copolymers. AZO can be selectively attached to the P4VP block of PS‐b‐P4VP through hydrogen bonding interactions. The assembly of AZO with vinylpyridine group‐containing polymers was initially investigated on a model system composed of P4VP homopolymer and AZO. Homogeneous liquid crystalline materials were obtained for ratios of AZO to vinylpyridine repeating unit, x, lower or equal to 0.50. Mixtures with higher x resulted in heterogeneous materials showing clear macrophase separation. Accordingly, a series of hydrogen‐bonded complexes of PS‐b‐P4VP and AZO, PS‐b‐P4VP(AZO)_x, with x = 0.25 and x = 0.50 were prepared. Lamellar and spherical morphologies were observed for the complexes based on PS24‐b‐P4VP9.5 (M_n,PS = 24,000, M_n,P4VP = 9500) and PS24‐b‐P4VP1.9 (M_n,PS = 24,000, M_n,P4VP = 1900), respectively. Photoinduced orientation of the azobenzene units was obtained in films of P4VP(AZO)_x and PS‐b‐P4VP(AZO)_x with x = 0.25 and 0.50 by using 488 nm linearly polarized light and characterized through birefringence and dichroism measurements. This investigation shows a versatile and less laborious approach to azobenzene‐containing polymer materials with low chromophore content, of interest in optical application. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Isoprene polymerization with indolide‐imine supported rare‐earth metal alkyl and amidinate complexes

Reaction of 7‐{(N‐2,6‐R)iminomethyl)}indole ( HL¹ , R = dimethylphenyl; HL² , R = diisopropylphenyl) and rare‐earth metal tris(alkyl)s, Ln(CH₂SiMe₃)₃(THF)₂, generated new rare‐earth metal bis(alkyl) complexes LLn(CH₂SiMe₃)₂(THF) [L = L¹: Ln = Lu ( 1a ), Sc ( 1b ); L = L²: Ln = Lu ( 3a ), Sc ( 3b )] and mono(alkyl) complexes L²₂Lu(CH₂SiMe₃) ( 4a ). Treatment of alkyl complexes 1a and 4a with N,N′‐diisopropylcarbodiimide afforded the corresponding amidinates L¹Lu{iPr₂NC(CH₂SiMe₃)NiPr₂}₂ ( 2a ) and L²₂Lu{iPr₂NC(CH₂SiMe₃)NiPr₂} ( 5a ), respectively. These new rare‐earth metal alkyls and amidinates except 4a in combination with aluminum alkyls and borate generated efficient homogeneous catalysts for the polymerization of isoprene, providing high cis‐1,4 selectivity and high molar mass polyisoprene with narrow molar mass distribution (M_n = 2.65 × 10⁵, M_w/M_n = 1.07, cis‐1,4 98.2%, −60 °C). The environmental hindrance around central metals arising from the bulkiness of the ligands, the Lewis‐acidity of rare‐earth metal ions, the types of aluminum tris(alkyl)s and borate, and polymerization temperature influenced significantly on both the catalytic activity and the regioselectivity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5251–5262, 2008     

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.     

Chelation versus Binucleation: Metal Complex Formation with the Hexadentate all‐cis‐N1,N2‐Bis(2,4,6‐trihydroxy‐3,5‐diaminocyclohexyl)ethane‐1,2‐diamine

The hexadentate ligand all‐cis‐N¹,N²‐bis(2,4,6‐trihydroxy‐3,5‐diaminocyclohexyl)ethane‐1,2‐diamine (L^e) was synthesized in five steps with an overall yield of 39 % by using [Ni(taci)₂]SO₄?4 H₂O as starting material (taci=1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol). Crystal structures of [Na_0.5(H₆L^e)](BiCl₆)₂Cl_0.5?4 H₂O ( 1 ), [Ni(L^e)]‐ Cl₂?5 H₂O ( 2 ), [Cu(L^e)](ClO₄)₂?H₂O ( 3 ), [Zn(L^e)]CO₃?7 H₂O ( 4 ), [Co(L^e)](ClO₄)₃ ( 5 c ), and [Ga(H_?2L^e)]‐ NO₃?2 H₂O ( 6 ) are reported. The Na complex 1 exhibited a chain structure with the Na⁺ cations bonded to three hydroxy groups of one taci subunit of the fully protonated H₆(L^e)⁶⁺ ligand. In 2 , 3 , 4 , and 5 c , a mononuclear hexaamine coordination was found. In the Ga complex 6 , a mononuclear hexadentate coordination was also observed, but the metal binding occurred through four amino groups and two alkoxo groups of the doubly deprotonated H_?2(L^e)^2?. The steric strain within the molecular framework of various M(L^e) isomers was analyzed by means of molecular mechanics calculations. The formation of complexes of L^e with Mn^II, Cu^II, Zn^II, and Cd^II was investigated in aqueous solution by using potentiometric and spectrophotometric titration experiments. Extended equilibrium systems comprising a large number of species were observed, such as [M(L^e)]²⁺, protonated complexes [MH_z(L^e)]^2+z and oligonuclear aggregates. The pK_a values of H₆(L^e)⁶⁺ (25 °C, μ=0.10 m ) were found to be 2.99, 5.63, 6.72, 7.38, 8.37, and 9.07, and the determined formation constants (log β) of [M(L^e)]²⁺ were 6.13(3) (Mn^II), 20.11(2) (Cu^II), 13.60(2) (Zn^II), and 10.43(2) (Cd^II). The redox potentials (vs. NHE) of the [M(L^e)]^3+/2+ couples were elucidated for Co (?0.38 V) and Ni (+0.90 V) by cyclic voltammetry.     

2‐{[Bis(2‐pyridylmethyl)amino]­methyl}‐6‐[(2‐hydroxy­anilino)­methyl]‐4‐methyl­phenol: a novel binucleating asymmetric ligand as a precursor to synthetic models for metalloenzymes

The title compound (H₂L), C₂₇H₂₈N₄O₂, is an asymmetric binucleating ligand with well defined soft (N₃O‐donor) and hard (NO₂‐donor) sides. H₂L was designed as a ligand for the preparation of heterodinuclear mixed‐valence M^III/M′^II complexes which are models for heterobimetallic active sites of enzymes, principally calcineurin. The mol­ecular structure of H₂L shows a spatial pre‐organization of the donor groups for coordination. This conformation is stabilized by bifurcated intra‐ and inter­molecular O—H⋯N hydrogen bonds involving both phenol groups. The inter­molecular hydrogen bonds link mol­ecules of H₂L into chains running parallel to the crystallographic c axis.     

Synthesis and UCST‐type phase behaviors of OEGylated random copolypeptides in alcoholic solvents

A series of OEGylated random copolypeptides with similar main‐chain lengths and different oligo(ethylene glycol) (OEG) molar content and chain lengths were prepared from triethylamine initiated ring‐opening polymerization (ROP) of OEGylated γ‐benzyl‐_L‐glutamic acid based N‐carboxyanhydride (OEG_mBLG–NCA, m = 2, 3) and γ‐benzyl‐_L‐glutamic acid based N‐carboxyanhydride (BLG–NCA). ¹H NMR analysis verified copolypeptides structures and determined the OEG molar content (x). FTIR analysis further confirmed the molecular structures, indicated α‐helical conformations of copolypeptides in the solid‐state, and revealed H‐bonding interactions between OEG pendants and alcoholic solvents. The copolypeptides exhibited a reversible upper critical solution temperature (UCST)‐type phase behavior in various alcoholic solvents (i.e., methanol, ethanol, 1‐propanol, 1‐butanol, and 1‐pentanol) depending on the x values and OEG side‐chain lengths (m). Variable‐temperature UV–vis analysis revealed that the UCST‐type transition temperatures (T_pts) of the copolypeptides in alcohols decreased as x or m value increased or as polymer concentration decreased. T_pts of copolypeptides with high x values (x ≥ 0.50) increased as the number of methylene of the alcoholic solvent increased from 3 (i.e., 1‐propanol) to 5 (i.e., 1‐pentanol). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3444–3453     

Voltammetric Determination of Phenoxybenzyl‐Type Insecticides at Chemically Modified Conducting Polymer‐Carbon Nanotubes Coated Electrodes

The electrochemical reduction of three common insecticides such as cypermethrin (CYP), deltamethrin (DEL) and fenvalerate (FEN) was investigated at glassy carbon electrode (GCE), multiwalled carbon nanotubes modified GCE (MWCNT‐GCE), polyaniline (herein called as modifier M₁) and polypyrrole (herein called as modifier M₂) deposited MWCNT/GCE using cyclic voltammetry. Influences of pH, scan rate, and concentration were studied. The surface morphology of the modified film was characterized by scanning electron microscopy (SEM) and X‐ray diffraction analysis (XRD). A systematic study of the experimental parameters that affect differential pulse stripping voltammetry (DPSV) was carried out and the optimized experimental conditions were arrived at. The calibration plots were linear over the insecticide's concentration range 0.1–100 mg L^?1 and 0.05–100 mg L^?1 for all the three insecticides at MWCNT‐GCE and MWCNT(M₁)‐GCE respectively. The MWCNT(M₂)‐GCE performed well among the three electrode systems and the determination range obtained was 0.01–100 mg L^?1 for CYP, DEL and FEN. The limit of detection (LOD) was 0.35 μg L^?1, 0.9 μg L^?1 and 0.1 μg L^?1 for CYP, DEL and FEN respectively on MWCNT(M₂)‐GCE modified system. Suitability of this method for the trace determination of insecticide in spiked soil sample was also determined.     

Nitridorhenium(V) Complexes with 1,3‐Dialkyl‐4,5‐dimethylimidazole‐2‐ylidenes

The nitridorhenium(V) complexes [ReNCl₂(PR₂Ph)₃] (R = Me, Et) react with the N‐heterocyclic carbenes (NHC) 1,3‐diethyl‐4,5‐dimethylimidazole‐5‐ylidene (L^Et) or 1,3,4,5‐tetramethylimidazole‐2‐ylidene (L^Me) in absolutely dry THF under complete replacement of the equatorial coordination sphere. The resulting [ReNCl(L^R)₄]⁺ complexes (L^R = L^Me, L^Et) are moderately stable as solids and in solution, but decompose in hot methanol under formation of [ReO₂(L^R)₄]⁺ complexes. With 1,3‐diisopropyl‐4,5‐dimethylimidazole‐5‐ylidene (L^i‐Pr), the loss of the nitrido ligand and the formation of a dioxo species is more rapid and no nitridorhenium intermediate could be isolated. The Re‐C bond lengths in [ReNCl(L^Et)₄]Cl of approximately 2.195Å are relatively long and indicate mainly σ‐bonding in the electron‐deficient d² system under study. The hydrolysis of the nitrido complexes proceeds via the formation of [ReO₃N]^2? anions as could be verified by the isolation and structural characterization of the intermediates [{ReN(PMe₂Ph)₃}{ReO₃N}]₂ and [{ReN(OH₂)(L^Et)₂}₂O][ReO₃N].     

Metal‐directed supramolecular architectures based on the bifunctional ligand 2,5‐bis(1H‐1,2,4‐triazol‐1‐yl)terephthalic acid

By the solvothermal reactions of 2,5‐bis(1H‐1,2,4‐triazol‐1‐yl)terephthalic acid (H₂L) with transition‐metal ions, two novel polymeric complexes, namely, poly[diaqua[μ₄‐2,5‐bis(1H‐1,2,4‐triazol‐1‐yl)terephthalato]cobalt(II)], [Co(C₁₂H₆N₆O₄)(H₂O)₂]_n, ( 1 ), and poly[[diaqua[μ₄‐2,5‐bis(1H‐1,2,4‐triazol‐1‐yl)terephthalato]nickel(II)] dihydrate], {[Ni(C₁₂H₆N₆O₄)(H₂O)₂]·2H₂O}_n, ( 2 ), were isolated. Both polymers have been characterized by FT–IR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction analysis. The complexes have similar two‐dimensional layered structures and coordination modes. Furthermore, the two‐dimensional layered structures bear distinct intermolecular hydrogen‐bonding interactions and π–π stacking interactions to form two different three‐dimensional supramolecular networks based on 4⁴‐subnets. The structural variation depends on the nature of the metal cations. The results of variable‐temperature magnetization measurements (χ_MT?T and χ_M^?1?T) show that complexes ( 1 ) and ( 2 ) display antiferromagnetic behaviour.     

Kohlenwasserstoffverbrückte Metallkomplexe. L Dicarbonyl‐cyclopentadienyl‐pyridoyl‐eisen‐Komplexe als Liganden

Hydrocarbon‐bridged Metal Complexes. L Dicarbonyl Cyclopentadienyl Pyridoyl Iron Complexes as Ligands Dicarbonyl‐cyclopentadienyl‐2‐ and 3‐pyridoyl‐iron (L¹, L²) and 2,6‐dicarbonyl‐pyridine‐bis(dicarbonyl‐cyclopentadienyl‐iron) (L³) function as ligands in metal complexes and the N,O‐chelates [(OC)₄M(L¹)] (M = Mo, W, 8 a, b ) and [(Ph₃P)₂Cu(L¹)]⁺BF₄^– ( 9 ) were prepared. Monodentate coordination of L¹ and L² through the pyridine N‐atom occurs in the palladium(II) complexes [Cl₂Pd(PnBu₃)(L¹)] ( 10 ), [Cl₂Pd(PnBu₃)(L²)] ( 11 ) and [Cl₂Pd(L²)₂] ( 12 ). Ligand L³ forms the O,N,O‐bis(chelate) [Cl₂Zn(L³)] ( 13 ). The crystal and molecular structures of L¹, 8 b (M = W), 9–11 and 13 were determined by X‐ray diffraction.     

Amidophosphine‐stabilized palladium complexes catalyse Suzuki–Miyaura cross‐couplings in aqueous media

We report a simple and efficient procedure for Suzuki–Miyaura reactions in aqueous media catalysed by amidophosphine‐stabilized palladium complexes trans‐{L³PPh₂}₂PdCl₂ ( 3 ), trans‐{L³PPhtBu}₂PdCl₂ ( 4 ), [Pd(η³‐C₃H₅)(L³PPh₂)Cl] ( 5 ) and {Pd[2‐(Me₂NCH₂)C₆H₄](L³PPh₂)Cl} ( 6 ). The acidity of the NH proton in complexes 3 , 4 , 5 , 6 plays an important role in their catalytic activity. In addition, the palladium complexes cis‐{L¹PPh₂}PdCl₂ ( 1 ) and trans‐{L²PPh₂}₂PdCl₂ ( 2 ) stabilized by phosphines containing Y,C,Y‐chelating ligands L^1,2 have also been found to be useful catalysts for Suzuki–Miyaura reactions in aqueous media. The method can be effectively applied to both activated and deactivated aryl bromides yielding high or moderate conversions. The catalytic activity of couplings performed in pure water increases when utilizing a Pd complex with more acidic NH protons. A decrease of palladium concentration from 1.0 to 0.5 mol% does not lead to a substantial loss of conversion. In addition, Pd complex 1 can be efficiently recovered using two‐phase system extraction. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of star‐shaped polystyrenes via nitroxide‐mediated stable free‐radical polymerization

High molecular weight star‐shaped polystyrenes were prepared via the coupling of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) terminated polystyrene oligomers with divinylbenzene (DVB) in m‐xylene at 138 °C. The optimum ratio of the coupling solvent (m‐xylene) to divinylbenzene was determined to be 9 to 1 based on volume. Linear polystyrene oligomers (M_n = 19,300 g/mol, M_w/M_n = 1.10) were prepared in bulk styrene using benzoyl peroxide in the presence of TEMPO at approximately 130 °C under an inert atmosphere. Coupling of the TEMPO‐terminated oligomers under optimum conditions resulted in a product with a number average molecular weight exceeding 300,000 g/mol (M_w/M_n = 3.03) after 24 h, suggesting the formation of relatively well‐defined star‐shaped polymers. Additionally, the intrinsic viscosities of the star‐shaped products were lower than calculated values for linear analogs of equivalent molecular weight, which further supported the formation of a star‐shaped architecture. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 216–223, 2001