Reactivity of AlMe3 with titanium(IV) Schiff base complexes: X-ray structure of [Ti{(μ-Br)(AlMe2)}{(μ-Br)(AlMe2X)}(salen)] · C7H8 (X=Me or Br) and reactivity studies of mono-alkylated [Ti(Me)X(L)] complexes

[TiCl₂(salen)] (1) reacts with AlMe₃ (1:2) to give the heterometallic Ti(III) and Ti(IV) complexes [Ti{(μ-Cl)(AlMe₂)}{(μ-Cl)(AlMe₂X)}(salen)] (X=Me or Cl) (2) and [TiMe{(μ-Cl)(AlCl₂Me)}(salen)] (3). Addition of diethyl ether to 3 affords [Ti(Me)Cl(salen)] (4). The analogous reaction of [TiBr₂(salen)] (5) gives the crystallographically characterised [Ti{(μ-Br)(AlMe₂)}{(μ-Br)(AlMe₂X)}(salen)] (X=Me or Br) (6) and [Ti(Me)Br(salen)] (7) in a single step, whilst the comparable reaction of [TiCl₂{(3-MeO)₂salen}] (8) with AlMe₃ yields [Ti(Me)Cl{(3-MeO)₂salen}] (9) with no evidence of titanium(III) species. Reactivity of both halide and methyl groups of 4 has been probed using magnesium reduction, SbCl₅ and AgBF₄ halide abstraction and SO₂ insertion reactions. Hydrolysis of [Ti(Me)X(L)] complexes affords μ-oxo species [TiX(L)]₂(μ-O) [X=Cl, L=salen (13); X=Br, L=salen (14); X=Cl, L=(3-MeO)₂salen (15)].     

A DFT Quantum‐Chemical Study of the Structure of Precursors and Active Sites of Catalyst Based on 2,6‐Bis(imino)pyridyl Fe(II) Complexes

Summary: A DFT method has been applied for quantum‐chemical calculations of the molecular structure of charge‐neutral complex LFeMe(μMe)₂AlMe₂ which is formed in system LFeMe₂ + AlMe₃ (L = 2,6‐bis(imino)pyridyl). Calculations suggested the formation of highly polarized complex LFeMe(μMe)₂AlMe₂ ( II ) in system LFeMe₂ + AlMe₃, characterized by r(Fe μMe) = 3.70 Å and r(Al μMe) = 2.08 Å and deficient electron density on fragment [LFeMe]^Q (Q = +0.80 e). Polarization of the complex progresses with the bounding of two AlMe₃ molecules (complex LFeMe(μMe)₂AlMe₂ · 2AlMe₃ ( III )) and with replacement of AlMe₃ by MeAlCl₂ (complex LFeMe(μMe)₂AlCl₂ ( IV )). The activation energy of ethylene insertion into the Fe Me bond of these complexes has been calculated. It was found that the heat of π‐complex formation increases with increasing of polarization extent in the order II < III < IV . Activation energy of the insertion of coordinated ethylene into Fe Me bond decreases in the same order: II > III > IV .

Calculated model complex (NH₃)₃FeMe₂; tridentate bis(imino)pyridyl ligand was substituted by three coplanar NH₃ groups.     

Synthesis and characterization of aluminum complexes based on amino‐benzotriazole phenoxide ligand: luminescent properties and catalysis for ring‐opening polymerization

Aluminum complexes coordinated by a ^C1DEABTP ligand (^C1DEABTP‐H = 2‐(2H‐benzotriazol‐2‐yl)‐6‐((diethylamino)methyl)‐4‐methylphenol) were synthesized and structurally characterized. The formation of Al complexes is dependent on the stoichiometry of AlMe₃ to ^C1DEABTP ligand ratio. The reaction of ^C1DEABTP‐H with AlMe₃ (1.0 molar equiv.) in hexane produced mono‐adduct aluminum complex [(^C1DEABTP)AlMe₂] (1), but treatment of ^C1DEABTP‐H with 2.0 molar equiv. of AlMe₃ afforded mixtures of [(^C1DEABTP)Al₂Me₅] (2) and [(^C1DEABTP)Al₃Me₈] (3). The penta‐coordinated bis‐adduct aluminum complex [(^C1DEABTP)₂AlMe] (4) was synthesized through the reaction of AlMe₃ with ^C1DEABTP‐H (2.0 molar equiv.) in hexane. Tri‐adduct Al complex [(^C1DEABTP)₃Al] (5) resulted from treatment of AlMe₃ with ^C1DEABTP‐H (3.0 equiv.); the Al center is hexa‐coordinated with three N,O‐bidentate ^C1DEABTP ligands. X‐ray diffraction of single crystals indicates that the bonding modes of the ^C1DEABTP ligands in complexes 2–3 are greatly affected when excess AlMe₃ is coordinated. The optical properties and catalysis for lactone polymerizations of ^C1DEABTP coordinated to Al complexes were tested. Tri‐adduct Al complex 5 produced an intense green fluorescence in both solution and the solid state. Complex 4 is an active catalyst for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and L‐lactide (L‐LA) in the presence of 9‐anthracenemethanol (9‐AnOH). In ε‐CL polymerization, Al complex 4 catalyzes efficiently in both a 'controlled' and 'immortal' manner, giving polymers with the expected molecular weights and narrow polydispersity indexes. Copyright © 2012 John Wiley & Sons, Ltd.     

Structure characterisation of the organoaluminium intermediate resulting from the alkylation of a chelated carbonyl group. Molecular structure of the trinuclear [MeAl][C12H20O4][AlMe2]2 compound

The interaction of Me₃Al with Me₂Al(acac) results in the carbonyl alkylation of the chelating acetylacetonate ligand and formation of trinuclear complex [MeAl][C₁₂H₂₀O₄][AlMe₂]₂ (1). The title compound has been characterised by ¹H-and ²⁷Al-NMR spectroscopy. The ¹H-NMR spectra are consistent with the presence of two distinct isomers in an equimolar ratio: cis-1 and trans-1. Both isomers contain two methylated acac units bridged by three organoaluminium moieties: central five-coordinated methyl aluminium species and two terminal four-coordinated dimethylaluminium species. The structure of cis-1 has been confirmed by X-ray crystallography which revealed that the five-coordinated aluminium atom rises in almost ideal square pyramidal geometry. The role of the molar ratio of reactants is discussed.     

Effect of trimethylaluminum on the formation of active sites of the catalytic system bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride—MAO and catalytic isomerization of hex-1-ene

The transformations of bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]-titanium(iv) dichloride (L₂TiCl₂) occurring in toluene under the action of methylalumoxane (MAO) were studied by ¹H NMR spectroscopy. The commercially available MAO containing trimethylaluminum (AlMe₃) and MAO free of AlMe₃ (the so called “dry” MAO) were used. The catalytic transformations of hex-1-ene involving the systems L₂TiCl₂-MAO were studied. We proposed the structures of the cationic titanium complexes formed in the absence and in the presence of hex-1-ene under the action of MAO. In the absence of olefin, neutral and cationic titanium complexes are decomposed under the action of AlMe₃ according to the exchange reaction of the complex ligand with the methyl groups of AlMe₃ to form LAlMe₂. The neutral complexes react considerably faster than the cationic ones. In the presence of olefin, decomposition of complexes under the action of AlMe₃ is suppressed. The titanium complex activated by “dry” MAO isomerizes hex-1-ene to hex-2-ene. In the presence of large amounts of TMA (commercial MAO), this reaction does not take place.     

Preparation of Aluminum Alkoxides and Crystal Structures of [Al{(S)-(-)-μ-OC(H)(CH3)C(Ph)2OH}Cl2]2·2Et2O and [(μ-O(CH2)2OPh)AlMe2]2

The reaction of (S)-(-)-1, l-diphenyl-propane-1,2-diol with AlCl₃ in diethyl ether furnishes the product [Al((S)-(-)-μ₂-OC(H)(Me)C(Ph)₂OH)Cl₂]₂ 1, which decomposes slowly above 25 °C. Complex 1·2Et₂O Crystallizes in the non-centrosymmetric monoclinic space group P2₁ with a=10.591(1) Å, b=16.718(1) Å, c = 12.156(2) Å, β=99.30(2)°, V = 2124.1(3) Å₃, z = 4, R = 4.67%, Rw=4.84%, GoF=1.14. The structure of 1 shows a dimer feature, which is hydrogen bonded to two diethyl ether molecules. In the reaction of 2-phenoxyethanol with AlMe₃, the dimeric [(μ-O(CH₂)₂OPh)AlMe₂]₂ is obtained in high yield. 2 crystallizes in the monoclinic space group P2₁/c with a = 7.398(2) Å, b = 7.376(2) Å, c = 20.710(2) Å, β = 90.56(2)°, v = 1129.9(4) ų, z=4, R=5.70%, Rw=7.15%, GoF=1.59.     

β‐Diketiminate Stabilized Magnesium Hydroxide,Heterobimetallic, and Halide Complexes: Synthesis and X‐ray Structural Studies

The controlled hydrolysis of heteroleptic magnesium amide, LMgN(SiMe₃)₂ (L = CH[C(Me)N(2,6‐iPr₂C₆H₃)]₂) with water afforded the corresponding hydroxide [LMg(OH)·THF]₂ as air and moisture sensitive compound. The presence of a sterically bulky β‐diketiminate ligand prevents the self‐condensation reaction of this hydroxide complex. Single crystal X‐ray analysis shows that the hydroxide is dimeric in the solid state. Reaction of the magnesium amide or LMg(Me)·OEt₂ with LAlMe(OH) generates the heterobimetallic species containing the Mg–O–Al moiety. Additionally, the reaction of methylmagnesiumchloride with the free ligand leads to complex L′MgCl (L′ = CH[Et₂NCH₂CH₂N(CMe)]₂). As revealed by the crystal structure, L′MgCl is a solvent free monomeric magnesium chloride complex that is analogues to the Grignard reagent.     

Reversible Addition of Carbon Dioxide to Main Group Metal Complexes at Temperatures about 0 °C

The reaction of dialane [LAl-AlL] ( 1 ; L=dianion of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene, dpp-bian) with carbon dioxide results in two different products depending on solvent. In toluene at temperatures of about 0 °C, the reaction gives cycloadduct [L(CO₂)Al-Al(O₂C)L] ( 2 ), whereas in diethyl ether, the reaction affords oxo-bridged carbamato derivative [L(CO₂)(Et₂O)Al(μ-O)AlL] ( 3 ). The DFT and QTAIM calculations provide reasonable explanations for the reversible formation of complex 2 in the course of two subsequent (2+4) cycloaddition reactions. Consecutive transition states with low activation barriers were revealed. Also, the DFT study demonstrated a crucial effect of diethyl ether coordination to aluminium on the reaction of dialane 1 with CO₂. The optimized structures of key intermediates were obtained for the reactions in the presence of Et₂O; calculated thermodynamic parameters unambiguously testify the irreversible formation of the product 3 .     

Luminescent Study on Nd3+ Complexes Containing Carboxylate‐Dithiolene and Alkoxide‐Dithiolene Ligands

Reaction of ligand L H₂ (4,5‐bis[carboxymethylthio]‐1,3‐dithiol‐2‐thione) with neodymium silyl‐amide (Nd[N(TMS)₂]₃; TMS= ‐SiMe₃), in a ratio 2:1, yields a neodymium‐dithiolene‐carboxylato complex ( 1 ) (Nd( L H) L ). Similarly, reaction of 2 equivalents of L′ H₂ (4,5‐bis[2′‐hydroxyethyl)thio]‐1,3‐dithiol‐2‐thione) and one equivalent of neodymium silyl‐amide (Nd[N(TMS)₂]₃) allowed the isolation of complex 2 , with a ligand:metal ratio of 3:2. ATR‐IR spectrum of 1 displays a broad band characteristic of an OH group showing that one carboxylate group remains protonated. Emission spectrum of complex 1 under excitation in the visible region (at 360 nm i.e. on the ligand) displayed typical emission bands of the Nd³⁺, showing that energy transfer from the ligand to the lanthanide was achieved (i.e. “antenna effect”). No significant quenching from the remaining –OH group was detected. In the case of complex 2 , the main emission bands characteristic of the Nd³⁺ ion have been observed, by excitation at 495 nm.     

Synthesis and structural characterisation of aluminium imino-amide and pyridyl-amide complexes: bulky monoanionic N,N chelate ligands via methyl group transfer

Treatment of the imines [ArN=CH-CH=NAr] and [ArN=CH-2-py] (Ar=2,6-Pr₂ⁱC₆H₃) with AlMe₃ in toluene affords the highly crystalline complexes [AlMe₂{ArN-CH₂-C(Me)=NAr}] (1) and [AlMe₂{ArN-CH(Me)-2-py}] (2); the molecular structures of 1 and 2 show that the aluminiums are bonded to imino-amide and pyridyl-amide ligands respectively arising from methyl group transfer from the aluminium centre to the backbone carbon of the imine ligand.     

To Coordinate or not to Coordinate: The Special Role of Chalcogen Ether Functionalities in the Design of Twofold Functionalized Cyclopentadienyl Ligands [Cp,O,Ch (Ch = S,Se)]

The solvent‐ and catalyst free synthesis of two β‐thio ketones L1a and L1b is reported. L1a , L1b , and a β‐seleno ketone L1c were successfully employed as ligand precursors in the synthesis of a novel series of cationic titanium complexes 4a – 4c via a well‐established reaction sequence: insertion of the carbonyl functional group into the polarized Ti–C_q,exo bond of the monopentafulvene complex Cp*Ti(Cl)(π‐η⁵:σ–η¹‐C₅H₄=CR₂) ( 1 ) (CR₂ = adamantylidene), subsequent methylation, and final activation with B(C₆F₅)₃. The cationic titanium complexes 4a – 4c bear twofold functionalized cyclopentadienyl [Cp,O,Ch (Ch = S, Se)] ligand frameworks built directly in the coordination sphere of the metal, in which the chalcogen ether functionalities do not coordinate to the central metal atoms as demonstrated by NMR experiments. Consequently, Cp,O σ,π chelating ligand systems are formed with free coordination sites at the central titanium atoms and pendant chalcogen ether moieties.     

[(CH3)Al(CH2)]12: Methylaluminomethylene (MAM-12)

The molecular structure of enigmatic “poly(aluminium-methyl-methylene)” (first reported in 1968) has been unraveled in a transmetalation reaction with gallium methylene [Ga₈(CH₂)₁₂] and AlMe₃. The existence of cage-like methylaluminomethylene moieties was initially suggested by the reaction of rare-earth-metallocene complex [Cp*₂Lu{(μ-Me)₂AlMe₂}] with excess AlMe₃ affording the deca-aluminium cluster [Cp*₄Lu₂(μ₃-CH₂)₁₂Al₁₀(CH₃)₈] in low yield (Cp*=C₅Me₅). Treatment of [Ga₈(CH₂)₁₂] with excess AlMe₃ reproducibly gave the crystalline dodeca-aluminium complex [(CH₃)₁₂Al₁₂(μ₃-CH₂)₁₂] (MAM-12). Revisiting a previous approach to “poly(aluminium-methyl-methylene” by using a (C₅H₅)₂TiCl₂/AlMe₃ (1 : 100) mixture led to amorphous solids displaying solubility behavior and spectroscopic features similar to those of crystalline MAM-12. The gallium methylene-derived MAM-12 was used as an efficient methylene transfer reagent for ketones.     

A Quantum Chemical Study of the Molecular Structure of Active Centers and Growth in Ethylene Polymerization in the Catalytic System LFeCl2/AlMe3 (L = 2,6-Bis-Iminopyridyl)

Density functional theory with hybrid exchange-correlation functional B3P86 is used to calculate the molecular structures of neutral Fe(II) complexes formed in the LFeCl₂/AlMe₃ system (L = tridentate bis(imine)pyridyl ligand). A simplified model of the LFeCl₂ complex is used in calculations, where L is replaced by three NH₃ ligands. Parameters of geometric and electronic structures of the complexes (NH₃)₃FeMe(-Me)AlMe₃ (I) and (NH₃)₃FeMe(-Me)₂AlMe₂ (IIA and IIB), which are the structures where the Fe-Me and Fe--Me groups are in one or two perpendicular planes, respectively, were determined. Complexes II, which were earlier identified using ¹H NMR spectroscopy, are more stable than complex I. Complex IIB is strongly polarized (the distances r(Fe--Me) and r(Al--Me) are 3.70 and 2.08 Å, respectively) and coordinatively unsaturated due to the transfer of the methyl group from (NH₃)₃FeMe₂ onto AlMe₃. It has significant electron density deficit in the coordination sphere of the transition metal [(NH₃)₃FeMe] ^Q (Q = +0.80e). The energetic profile of the reaction of ethylene addition to the Fe-Me bond for the complexes (NH₃)₃FeMe₂, IIA and IIB, was calculated. It was shown that, compared to (NH₃)₃FeMe₂, a drastic decrease in the activation energy of ethylene addition is observed in the case of IIB (from 135 to 66 kJ/mol). The reason for the more efficient activation of the complexes LFeMe₂ by a weak Lewis acid (AlMe₃) and for the increased reactivity of the metal-alkyl bond in complex IIB compared to the zirconocene complex Cp₂ZrMe₂ is discussed.     

Di‐nuclear zinc complexes containing tridentate imino‐benzotriazole phenolate derivatives as efficient catalysts for ring‐opening polymerization of cyclic esters and copolymerization of phthalic anhydride with cyclohexene oxide

Zinc catalysts incorporated by imino‐benzotriazole phenolate ( IBTP ) ligands were synthesized and characterized by single‐crystal X‐ray structure determinations. The reaction of the ligand precursor ( ^C1DMeIBTP ‐H or ^C1DIPIBTP ‐H) with diethyl zinc (ZnEt₂) in a stoichiometric proportion in toluene furnished the di‐nuclear ethyl zinc complexes [(μ‐ ^C1DMeIBTP )ZnEt]₂ ( 1 ) and [(μ‐ ^C1DIPIBTP )ZnEt]₂ ( 2 ). The tetra‐coordinated monomeric zinc complex [( ^C1PhIBTP )₂Zn] ( 3 ) or [( ^C1BnIBTP )₂Zn] ( 4 ) resulted from treatment of ^C1PhIBTP ‐H or ^C1BnIBTP ‐H as the pro‐ligand under the similar synthetic method with ligand to metal precursor ratio of 2:1. Single‐crystal X‐ray diffraction of bimetallic complexes 1 and 2 indicates that the ^C1DMeIBTP or ^C1DIPIBTP fragment behaves a NON‐tridentate ligand to coordinate two metal atoms. Catalysis for ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL), β‐butyrolactone (β‐BL), and lactide (LA) of complexes 1 and 2 was systematic studied. In combination with 9‐anthracenemethanol (9‐AnOH), Zn complex 1 was found to polymerize ε‐CL, β‐BL, and L‐LA with efficient catalytic activities in a controlled character. This study also compared the reactivity of these ROP monomers with different ring strains by Zn catalyst 1 in the presence of 9‐AnOH. Additionally, Zn complex 1 combining with benzoic acid was demonstrated to be an active catalytic system to copolymerize phthalic anhydride and cyclohexene oxide. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 714–725     

Ring opening polymerization of lactide promoted by alcoholyzed heteroscorpionate aluminum complexes

The alcoholysis of the heteroscorpionate methyl aluminum complex (bpzmp)AlMe₂ ( 1 ) (bpzmp = 2,4‐di‐tert‐butyl‐6‐(bis‐(3,5‐dimethylpyrazol‐1‐yl)methyl)phenoxo), promoted both by phenol and isopropanol, has been investigated. The reaction of 1 with phenol afforded the dimeric mono(phenoxo) derivative 2 , whereas the alcoholysis of 1 with the less acidic isopropanol involved the coordinated heteroscorpionate ligand and led to the tetrahedral complex 3 in which the aluminum atom is surrounded by one κ²‐N,O^? coordinated bpzmp ligand and one η¹‐O^? coordinated ppzmp ligand (ppzmp = 2,4‐di‐tert‐butyl‐6‐(i‐propoxy‐(3,5‐dimethylpyrazol‐1‐yl)methyl)phenoxo). Complexes 1 – 3 have been tested in the ring opening polymerization (ROP) of L ‐lactide. The dimeric mono(phenoxo) derivative 2 was inactive in the ROP of L ‐lactide. Quite surprisingly, complex 3 was found to be active in ROP of L ‐ and rac‐lactide, showing a good molar‐mass control. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3632–3639, 2010     

3-乙基-2-乙酰吡嗪缩4-苯基氨基脲Ag(I)配合物的合成、结构和DNA结合性质

合成并通过单晶衍射、元素分析及红外光谱表征了配合物[Ag₂（HL）（NO₃）₂]_n（1）的结构（HL为3-乙基-2-乙酰吡嗪缩4-苯基氨基脲）。单晶衍射结果表明,配合物1中,HL作为中性四齿配体连接2个Ag（I）中心,其中一个Ag（I）中心与HL配体中的ON₂供体（羰基O,亚胺N和吡嗪N1原子）和2个单齿硝酸根配位,构成扭曲的四方锥配位构型;而另一个Ag（I）离子与1个单齿硝酸根,1个双齿硝酸根和HL配体中的吡嗪N4原子配位,形成扭曲平面正方形配位构型。另外,相邻的Ag（I）离子通过桥联的硝酸根离子相互连接形成二维层状结构;此外,配合物1与DNA的相互作用强于配体。     

Rare‐Earth‐Metal Alkylaluminates Supported by N‐Donor‐Functionalized Cyclopentadienyl Ligands: C?H Bond Activation and Performance in Isoprene Polymerization

Homoleptic tetramethylaluminate complexes [Ln(AlMe₄)₃] (Ln=La, Nd, Y) reacted with HCp^NMe2 (Cp^NMe2=1‐[2‐(N,N‐dimethylamino)‐ethyl]‐2,3,4,5‐tetramethyl‐cyclopentadienyl) in pentane at ?35 °C to yield half‐sandwich rare‐earth‐metal complexes, [{C₅Me₄CH₂CH₂NMe₂(AlMe₃)}Ln(AlMe₄)₂]. Removal of the N‐donor‐coordinated trimethylaluminum group through donor displacement by using an equimolar amount of Et₂O at ambient temperature only generated the methylene‐bridged complexes [{C₅Me₄CH₂CH₂NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] with the larger rare‐earth‐metal ions lanthanum and neodymium. X‐ray diffraction analysis revealed the formation of isostructural complexes and the C? H bond activation of one aminomethyl group. The formation of Ln(μ‐CH₂)Al moieties was further corroborated by ¹³C and ¹H‐¹³C HSQC NMR spectroscopy. In the case of the largest metal center, lanthanum, this C? H bond activation could be suppressed at ?35 °C, thereby leading to the isolation of [(Cp^NMe2)La(AlMe₄)₂], which contains an intramolecularly coordinated amino group. The protonolysis reaction of [Ln(AlMe₄)₃] (Ln=La, Nd) with the anilinyl‐substituted cyclopentadiene HCp^AMe2 (Cp^AMe2=1‐[1‐(N,N‐dimethylanilinyl)]‐2,3,4,5‐tetramethylcyclopentadienyl) at ?35 °C generated the half‐sandwich complexes [(Cp^AMe2)Ln(AlMe₄)₂]. Heating these complexes at 75 °C resulted in the C? H bond activation of one of the anilinium methyl groups and the formation of [{C₅Me₄C₆H₄NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] through the elimination of methane. In contrast, the smaller yttrium metal center already gave the aminomethyl‐activated complex at ?35 °C, which is isostructural to those of lanthanum and neodymium. The performance of complexes [{C₅Me₄CH₂CH₂NMe(μ‐CH₂)AlMe₃}‐ Ln(AlMe₄)], [(Cp^AMe2)Ln(AlMe₄)₂], and [{C₅Me₄C₆H₄NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] in the polymerization of isoprene was investigated upon activation with [Ph₃C][B(C₆F₅)₄], [PhNMe₂H][B(C₆F₅)₄], and B(C₆F₅)₃. The highest stereoselectivities were observed with the lanthanum‐based pre‐catalysts, thereby producing polyisoprene with trans‐1,4 contents of up to 95.6 %. Narrow molecular‐weight distributions (M_w/M_n<1.1) and complete consumption of the monomer suggested a living‐polymerization mechanism.     

Isolation of the complex between acrylonitrile and trimethylaluminum

The complex of acrylonitrile (AN) with trimethylaluminum (AlMe₃) was successfully isolated as a white needlelike crystal with a melting point of 42.5°C. In this article the preparation of the complex is described in detail. Cryoscopic and spectral investigations indicated that the complex is formed by an equimolar ratio of AN and AlMe₃. From the measurement of the x-ray diffraction photograph of the crystal the repeat period was determined to be 9.47 ± 0.05 Å.     

Synthesis, crystal structures and antibacterial activities of schiff base ligand and its cobalt(II) complex

The Schiff base ligand, HL · 0.5C₂H₅OH (HL = methyl N-[(4-chlorophenyl)(3-methyl-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-4-ylindene)methyl]valine), was derived from condensation of 1-phenyl-3-methyl-4-(p-chlorbenzyl)-5-pyrazolone with L-valine methyl ester in a 1: 1 molar ratio in methanol, ether and isopropanol solution. Reaction of ligand with Co(ClO₄)₂ · 6H₂O (in a 2: 1 molar ratio) in methanol solution afforded a mononuclear cobalt(II) complex, [Co(L)₂] (I). Molecular structures of HL · 0.5C₂H₅OH and complex I were characterized by elemental analysis, IR and single crystal X-ray diffraction analysis. The enamine-keto form of the ligand has turned to imine form in complex I. Each Co(II) center in complex I is in a octahedral N₂O₄ coordination sphere. Both the Schiff base ligand and its Co(II) complex have been tested in vitro with agar dilution method to evaluate their antibacterial activity against bacteria Escherichia coli and Staphylococcus aureus. It has been found that they have higher activity against Escherichia coli than Staphylococcus aureus, and complex I has higher activity than HL · 0.5C₂H₅OH against the same bacteria.     

Platinum(IV) complexes with α,ω-bis(pyrazol-1-yl) alkanediyl and diethyl ether/thioether ligands. Crystal structures of dibromodimethyl[1,2-bis(pyrazol-1-yl)ethane]platinum(IV) and trimethyl-bis[2-(pyrazol-1-yl)ethyl]etherplatinum(IV) tetrafluoroborate

Reactions of the flexible α,ω-bis(pyrazol-1-yl) compounds 1,2-bis(pyrazol-1-yl)ethane (L1), 1,8-bis(pyrazol-1-yl)-n-octane (L2), bis[2-(pyrazol-1-yl)ethyl]ether (L3) and bis[2-(pyrazol-1-yl)ethyl]thioether (L4) with precursor organometallic platinum complexes ([(PtBr₂Me₂)_n], [(PtIMe₃)₄] and [(PtMe₂(cod)]/I₂) are described herein. The spectroscopic characterization of the platinum(IV) products of these reactions [PtBr₂Me₂{pz(CH₂)_mpz}], m = 2 (1) or 8 (2), [PtI₂Me₂{pz(CH₂)₂pz}] (3), [PtMe₃(pzCH₂CH₂OCH₂CH₂pz)][BF₄] (4) and [PtMe₃(pzCH₂CH₂SCH₂CH₂pz)][CF₃SO₃] (5), where ‘pz’ is pyrazol-1-yl, is discussed. Furthermore, solid state structures of 1, a complex with a seven-membered chelate ring, and 4, a complex bearing the neutral κ²N,N′,κO ligand bis[2-(pyrazol-1-yl)ethyl]ether (L3) are reported.