On the Development of Titanium κ1-Amidinate Complexes,Commercialized as Keltan ACE™ Technology,Enabling the Production of an Unprecedented Large Variety of EPDM Polymer Structures

ARLANXEO Elastomers has developed and commercialized Keltan ACE™ technology, a class of half-sandwich cyclopentadienyl κ¹-amidinate metal complexes, which are extremely active for the production of first-class ethylene/propylene/diene copolymers (EPDM). In this review, the development and some of the key features of the Keltan ACE™ catalyst system are presented. Many different ACE catalysts have been synthesized over the past years, including bridged and bimetallic catalysts. With Keltan ACE™, a complete range of EPDM products with similar polymer characteristics as their Ziegler–Natta (ZN) counterparts can be produced, including variations containing very high 5-ethylidene-2-norbornene (ENB) contents, controlled long chain branching, very high molecular weight, as well as oil-extended products. Moreover, other EPDM structures can be polymerized. The Keltan ACE™ catalyst technology also allows the production of EPDMs with very high amounts of dicyclopentadiene (DCPD) or 5-vinyl 2-norbornene (VNB) without excessive gelation and reactor fouling, that is, products that cannot or are extremely difficult to obtain via classical ZN catalysis. In a next step, high-VNB-EPDM can be postreactor modified, for example, via metathesis chemistry. In addition, EPDM polymers with a very broad or even bimodal molecular weight distribution can be obtained in a single reactor with certain ACE catalyst structures at particular activator/precatalyst ratios. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2877–2891     

Evidence of an equilibrium between selenides and osmium(VIII) reagents and selenoxides and osmium(VI) reagents

Driving the equilibrium between selenides and osmium(VIII) reagents with selenoxides and osmium(VI) by a subsequent reaction (rearrangement of allyl selenoxides to allyl alcohols or addition of osmium(VIII) species on C=C double bonds) to one side, allows the transformation of methyl geranyl selenides to linalool and of methyl citronellyl selenoxide to 6,7-dihydroxy citronellyl selenide.     

Polyferrocenylsilane microspheres: synthesis,mechanism of formation,size and charge tunability,electrostatic self-assembly,and pyrolysis to spherical magnetic ceramic particles

Pt(0)-catalyzed ring-opening precipitation copolymerization of [1]silaferrocenophanes fcSiMe(2) (3) and the spirocyclic cross-linker fcSi(CH(2))(3) (4) (fc = Fe(eta(5)-C(5)H(4))(2)) was used to prepare polyferrocenylsilane microspheres (PFSMSs) under mild conditions. By varying the reaction conditions, a wide variety of other morphologies was obtained. The effects of temperature, monomer ratio, solvent composition, catalyst concentration, and time on the observed morphology were investigated and interpreted in terms of a mechanism for microsphere formation. The most well-defined particles were formed using equimolar amounts of 3 and 4, in a 50:50 mixture of xylenes and decane at 60 degrees C with gentle agitation. Chemical oxidation of the polymeric microspheres led to positively charged particles (OPFSMSs) which underwent electrostatically driven self-assembly with negatively charged silica microspheres to form core-corona composite particles. Redox titration with controlled amounts of the one-electron oxidant [N(C(6)H(4)Br-p)(3)][PF(6)] in acetonitrile led to the oxidation of the outer 0.15 microm (ca. 32%) of the PFSMSs. The resulting OPFSMSs were reduced back to their neutral form by reaction with hydrazine in methanol. Pyrolysis of the PFSMSs led to spherical magnetic ceramic replicas with tunable magnetic properties that organize into ordered 2-D arrays at the air-water interface under the influence of a magnetic field.     

The isolation and X-ray structure of a complex between lithium picrate and dibenzo-36-crown-12

The crystal structure of 2Li picrate.dibenzo-36-crown-12.2H₂O was determined by X-ray diffraction methods. The 2:1 (metal:ligand) complex crystalli     

Molecular adjustment of the electronic properties of nanoporous electrodes in dye-sensitized solar cells

Molecular modification of dye-sensitized, mesoporous TiO2 electrodes changes their electronic properties. We show that the open-circuit voltage (V(oc)) of dye-sensitized solar cells varies linearly with the dipole moment of coadsorbed phosphonic, benzoic, and dicarboxylic acid derivatives. A similar dependence is observed for the short-circuit current density (I(sc)). Photovoltage spectroscopy measurements show a shift of the signal onset as a function of dipole moment. We explain the dipole dependence of the V(oc) in terms of a TiO2 conduction band shift with respect to the redox potential of the electrolyte, which is partially followed by the energy level of the dye. The I(sc) shift is explained by a dipole-dependent driving force for the electron current and a dipole-dependent recombination current.