An ab initio study of ionic liquid silver complexes as carriers in facilitated olefin transport membranes

Liquid phase isoprene/n-pentane mixtures can be separated through the use of facilitated transport membranes containing complexes of silver ions with an ionic liquid (IL). 1-Butyl-3-methyl imidazolium tetrafluoroborate and zwitterion-type imidazolium compounds containing covalently-bound sulfonate groups form complexes with AgX (X = BF₄, NO₃, and ClO₄). Facilitated isoprene transport has been observed with selectivities that depend on the counteranion of the silver salt. The facilitated transport phenomena of the olefin and IL/silver complexes were investigated theoretically by calculating their complexation energies (i.e., the energy of formation of the silver complexes with the olefin) with the density functional theory method. Among polymer/silver salt systems, the polymer/AgBF₄ system has been found to be generally more favorable for facilitated olefin transport than the polymer/AgNO₃ system because of the low lattice energy of AgBF₄. However, there is a different trend for IL/AgX systems. This difference may arise because the positively charged components of the IL can interact with the anions of the silver salt, which changes the olefin complexation activity. For IL/AgX systems, the selectivity varies inversely with the complexation energy, which implies that the diffusion of the carrier may be the significant factor affecting isoprene/n-pentane separation, once the appropriate complexation has occurred between olefin molecules and the ILsilver complexes.     

The (butadiene)zirconocene route to active homogeneous olefin polymerization catalysts

(Butadiene)zirconocene is observed to exist as an equilibrium mixture of (s-cis-) and (s-trans-η⁴-C₄H₆)ZrCl₂ isomers. The system adds a variety of unsaturated organic reagents to form metallacyclic (allyl)metallocene products. In some cases, a second equivalent of a reagent is taken up, which forms the basis of a variety of useful template coupling reactions of butadiene at the bent metallocene framework. The Lewis acid B(C₆F₅)₃ adds to (butadiene)zirconocene and to a great variety of butadiene complexes of ansa-metallocenes and related systems to give zwitterionic metallocene-butadiene-borate betaines. Most of these systems are active homogeneous Ziegler-Natta olefin polymerization catalysts, that do not require additional activation. Catalyst activities are often in a similar range to those observed for other catalyst activation procedures used in this chemistry. In the case of the (butadiene)metallocene/B(C₆F₅)₃ systems we can often observe the first olefin insertion step. This feature was utilized to carry out a variety of mechanistic studies of the essential carbon-carbon coupling steps that take place at such bent metallocene catalyst systems. Even reactions with the functionalized monomer methylmetacrylate could be followed in this way. Some chelate ligand late metal systems were also included in these studies. However, these systems mostly behaved differently, even in cases where some structural similarities were observed.     

A novel method for the synthesis of chiral epoxides from styrene derivatives using chiral acids in presence of Pseudomonas lipase G6 [PSL G6] and hydrogen peroxide

Chiral epoxidation of styrene and its derivatives was carried out using series of chiral acids and urea hydrogen peroxide (UHP) or aqueous hydrogen peroxide (50%) in two phases under the catalytic influence of immobilized Pseudomonas lipase G6 [PSL G6] at 25-55 °C. A moderate to good yield and enantioselectivities of chiral epoxides were obtained.     

High‐valent Molybdenum Imido Complexes with Tethered Olefins

Against the background of the (propene)Mo(=O)(=NH) and (allyl)Mo(=O)(=NH) surface species suggested as intermediates of the SOHIO process the potential of H₂N–C₆H₄–CH₂– CH=CH–CH₃, ( I ), for the introduction of chelating imido/olefin or imido/allyl ligands at highvalent Mo centres was tested. Reaction of I with Na₂[MoO₄] and trimethylchlorosilane yielded [Cl₂Mo(=N–C₆H₄–CH₂–CH=CH–CH₃)₂(dme)] ( 1 ), containing pendant olefinic arms. All attempts to introduce the olefin into the coordination sphere of the Mo centre failed. The same observation was made with [Cl₂Mo(=O)(=N–C₆H₄–CH₂–CH=CH–CH₃)(dme)] ( 2 ), synthesised via a commutation reaction from 1 and[(dme)Cl₂Mo(=O)₂]. Reaction of three equivalents of I with [CpMoCl_4′] yields [CpCl₂Mo(=N–C₆H₄–CH₂–CH=CH–CH₃)], ( 3 ), again with a pendant olefin arm; the products of experiments aiming at coordinating it to the Mo atom eluded isolation. I thus does not seem suitable for the synthesis of complexes with imido/olefin or imido/allyl ligands. However, products 1 – 3 , (two of which ( 1 , 3 ) were also characterised by single crystal X‐ray diffraction) are nevertheless interesting, e.g., with respect to the grafting of molybdenum complexes on the surfaces of solid supports to obtain heterogeneous oxidation catalysts.     

Coordination chemistry of the activation of [(triazacyclohexane)CrCl3] with [PhNMe2H][B(C6F5)4] and AlR3

Complexes of N-substituted 1,3,5-triazacyclohexanes with CrCl₃ form 1:1 adducts with [PhNMe₂H][B(C₆F₅)₄] with increased solubility in toluene. Addition of AlⁱBu₃ leads to free PhNMe₂ and a complex with [B(C₆F₅)₄]⁻ weakly coordinated to chromium via a meta-fluorine atom. This complex can polymerise and/or trimerise olefins similar to methyl aluminoxane activated complexes. Decomposition of the active complex involves transfer of the triazacyclohexane to aluminium leading to [(triazacyclohexane)AlⁱBu₂][B(C₆F₅)₄] and [(arene)₂Cr][B(C₆F₅)₄]. These chromium(I) complexes have been characterised by X-ray crystallography and prove that chromium is reduced to the oxidation state +I during the catalysis.     

Synthesis and properties of Zr-Co heterodinuclear complexes with a bridging bis(cyclopentadienyl) ligand

[(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(C₅H₅)] reacted with Co₂(CO)₈ to produce a heterodinuclear Zr(IV)-Co(I) complex [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)Co(CO)₂] (3). Complex 3 underwent oxidative addition of I₂ to give [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)CoI₂(CO)] (4) having Zr(IV) and Co(III) centers. The carbonyl ligand of 4 was easily replaced with P(OMe)₃ and PPh₃ to afford [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)CoI₂(L)] (5: L = P(OMe)₃, 6: L = PPh₃). Structures of 5 and 6 were determined by X-ray crystallography. These Zr-Co heterodinuclear complexes catalyzed polymerization of ethylene and propylene.     

In situ grafting of cyclopentadienyl-molybdenum complexes on mesoporous materials: The reaction of [η-CpMo(CO)3]Na with surface fixed iodo-benzyl siloxane

Na⁺[η⁵-CpMo(CO)₃]⁻ is grafted on aromatic silane (iodo-benzyl trimethoxy silane) modified surfaces of MCM-41 and MCM-48 molecular sieves. The XRD, N₂ adsorption-desorption, and TEM analysis provide strong evidence that the mesoporous structure of the supporting materials retains its long range ordering after the grafting process, despite significant reductions of the surface area, pore-volume and pore size. The appearance of strong IR bands around 2016 and 1956 cm⁻¹ as well as 3010 cm⁻¹ on the grafted samples showing the presence of carbonyl as well as aromatic functional groups, evidences the successful grafting of the η⁵-CpMo(CO)₃ complexes. Elemental analysis reveals 6.4 and 8.3 wt% Mo on the SM-41ASG and SM-48ASG samples, respectively. The appearance of new ²⁹Si CP MAS-NMR peaks around −61.4, and −69.6 ppm (T₂ and T₃) indicates the esterification of silanol groups by the methoxy group of the silane ligand. The samples prepared by this in situ method show high loading of Mo and also good catalytic activity and selectivity for olefin-epoxidation.     

Organometallic chemistry of 15-membered tri-olefinic macrocycles: catalysis by palladium(0) complexes in carbon-carbon bond-forming reactions

15-Membered macrocycles (E,E,E)-1,6,11-tris(arenesulfonyl)-1,6,11-triazacyclopentadeca-3,8,13-trienes (1) are prepared from arenesulfonamides and trans-1,4-dibromo-2-butene. Macrocycles 1 coordinate palladium(0), platinum(0), and silver(I). The palladium complexes are useful and reutilizable catalysts or precatalysts in Suzuki cross-couplings, butadiene telomerizations, hydroarylation of alkynes, and in the Heck reaction. Structurally related macrocycles are also available by similar synthetic procedures.     

新型二茂锆化合物(1,2-Ph2-4-PrCp)2ZrCl2的合成及催化烯烃聚合反应研究

3,4-二苯基环戊-2-烯-1-酮与丙基锂反应,经酸化脱水得新环戊二烯衍生物1,2-二苯基-4-丙基-1,3-环戊二烯(1).用丁基锂处理1得到相应的环戊二烯基锂,再与ZrCl₄在甲苯中反应,生成大立体阻碍二氯二茂锆化合物(1,2-Ph₂-4-PrCp)₂ZrCl₂(2).化合物1和2均经元素分析和核磁共振谱学表征.经甲基铝氧烷(MAO)活化,化合物2在较低Al/Zr比条件下既可有效地催化乙烯聚合,生成高分子量、高熔化温度聚乙烯.2/MAO体系对丙烯聚合表现出高活性,生成低分子量齐聚物,其分子量随聚合温度的降低而升高.