Oxidative activation of light alkanes on dense ionic oxygen conducting membranes

The oxidative dehydrogenation of ethane to ethylene (ODHE) has been studied in a catalytic membrane reactor (CMR) using a dense mixed ionic oxygen and electronic conducting perovskite membrane Ba0.5Sr0.5Co0.8Fe0.2O3-&. At 1080K, an ethylene yield of 66% was obtained with the bare membrane. After Pd cluster deposition, the ethylene yield reached 76% at 1050K. Ni cluster deposition led to a decrease of ethane conversion compared to the bare membrane without changing ethylene selectivity.

Temperature sensitivity of soil respiration is affected by prevailing climatic conditions and soil organic carbon content: A trans-China based case study

National Natural Science Foundation of China [30590381]; Knowledge Innovation Program of the Chinese Academy of Sciences [KZCX2YW-432]; International Partnership Project

Thiophene-NPN Ligand Supported Rare-Earth Metal Bis(alkyl) Complexes. Synthesis and Catalysis toward Highly trans-1,4 Selective Polymerization of Butadiene

A series of new rare-earth metal bis(alkyl) complexes [L(1-3)Ln(CH2SiMe3)(2)(THF)(n)] (L-1 = MeC4H2SCH2NC6H4(Ph)(2)P=NC6H2Me3-2,4,6: Ln = Sc, n = 1 (1a); Ln = Lu, n = 1 (1b); L-2 = MeC4H2SCH2NC6H4(Ph)(2)P=NC6H3Et2-2,6: Ln = Sc, n = 1 (2a); Ln = Lu, n = 1 (2b); Ln = Y, n = 1 (2c); L-3 = MeC4H2SCH2NC6H4(Ph)(2)P=(NC6H3Pr2)-Pr-i-2,6: Ln = Sc, n = 0 (3a)) and (LSc)-Sc-4(CH2SiMe3)(2()THF) (4a) (L-4 = C6H5CH2NC6H4(Ph)(2)P=NC6H3Et2-2,6) have been prepared by reaction of rare-earth metal tris(alkyl)s with the corresponding HL1-4 ligands via alkane elimination.

O-2 activation and hydrolysis of Salan rare-earth metal alkyl complexes

Salan ligated yttrium alkyl complex 1, (LY)-Y-1(CH2SiMe3)(THF) (Salan = L-1: [2-O-3,5-tBu(2)-C6H2CH2N(CH3) CH2](2)), was exposed to an oxygen/ nitrogen atmosphere to give a bimetallic alkoxide complex 4, [(LY)-Y-1(mu-OCH2SiMe3)](2). Whilst the lutetium counterparts 2 ((LLu)-Lu-1(CH2SiMe3)(THF)) and 3 ((LLu)-Lu-2(CH2SiMe3)(THF); L-2: [2-O-3-tBu-C6H2CH2N(CH3) CH2](2)) were hydrolysed with moist nitrogen to afford mixed hydroxy/silyloxy complexes 5 and 6 ([(LLu)-Lu-1,2(mu-OSiMe3)(mu-OH) LuL1,2]), respectively.

Metal dependent control of cis-/trans-1,4 regioselectivity in 1,3-butadiene polymerization catalyzed by transition metal complexes supported by 2,6-bis[1-(iminophenyl)ethyl]pyridine

Fe(III), Cr(III), Fe(II), Co(II) and Ni(II) chloride complexes supported by 2,6-bis[1-(iminophenyl)ethyl]pyridine have been synthesized and characterized along with single crystal X-ray diffraction. These complexes, in combination with MAO, have been examined in butadiene polymerization. The catalytic activity and regioselectivity are strongly controlled by metal center and cocatalyst (MAO/Co ratio dependent in the case of Co(II) complex). The activity decreases in the order of Fe(III) > Co(II) > Cr(III) approximate to Ni (II) complexes, in consistent with the space around the metal center. Polybutadiene with different microstructure content, from high trans-1,4 units (88-95% for iron(III) and Cr(III)), medium trans-1,4 and cis-1,4 units (55% and 35%, respectively, for iron(II)) to high cis-1,4 units 79% for Co(II) and 97% for Ni(II) call be easily achieved by varying of the metal center.

Methyleneimidazoline Complexes of Iridium, Rhodium, and Palladium from Selective C(sp(3))-H Bond Activation

Palladium, iridium, and rhodium complexes of 2-methyleneimidazolines have been synthesized by selective phosphine-assisted activation of the 2-methyl C-H bonds in 2-methylimidazolium compounds. Metallacycles of various sizes were obtained in the reaction of phosphine-tethered 2-methylimidazolium compounds and [{M(cod)X}(2)] (M = Rh or Ir cod = 1,5-cyclooctadiene: X = alkoxyl or Cl). representative complexes were characterized by X-ray crystallography. The selectivity for aliphatic C(sp(3))H versus aromatic C(sp(2))H activation could be adjusted by means of the steric bulk of the OR ligand, whereby a bulky, OR group favors activation of the 2-methyl C(sp(3))-H bond. Experimental results confirmed that a methyl C-H activation product (a seven-membered iridacycle) is the kinetic product, while the aryl C-H activation product (a six-membered iridacycle) is the thermodynamic product.

C-H activation motivated by N,N '-diisopropylcarbodiimide within a lutetium complex stabilized by an amino-phosphine ligand

A lutetium bis( alkyl) complex stabilized by a flexible amino phosphine ligand LLu( CH2Si(CH3)(3))(2)(THF) (L = (2,6-C6H3( CH3)(2)) NCH( C6H5) CH2P(C6H5)(2)) was prepared which upon insertion of N, N'-diisopropylcarbodiimide led to C-H activation via metalation of the ligand aryl methyl followed by reduction of the C=N double bond.

Temperature and pressure dependence of phase separation of trans-decahydronaphthalene/polystyrene solution

The cloud-point temperatures (T-c1's) of ti-ans-decahydronaphthalene (TD)/polystyrene (PS, M-w = 270 kg/mol) solutions were determined by fight scattering measurements over a range of temperatures (1-16 degreesC), pressures (100-900 bar), and compositions (4.2-21.6 vol% polymer). The system phase separates upon cooling and the T-c1 was found to increase with the rising pressure for the constant composition. In the absence of special effects this finding indicates positive excess volumes. The special attention was paid to the demixing temperatures as a function of the pressure for the different polymer solutions and the plots in the T-volume fraction plane and P-volume fraction plane. The cloud-point curves of polymer solutions under changing pressures were observed for different compositions, demonstrates that the TD/PS system exhibits UCST (phase separation upon cooling) behavior. With this data the phase diagrams under pressure were calculated applying the Sanchez-Lacombe (SL) lattice fluid theory. Furthermore, the cause of phase separation, i.e., the influence of Flory-Huggins (FH) interaction parameter under pressure was investigated.

Synthesis and properties of polyimides derived from cis- and trans-1,2,3,4-cyclohexanetetracarboxylic dianhydrides

Cis-1,2,3,4-cyclohexanetetracarboxylic dianhydride (cis-1,2,3,4-CHDA) was synthesized. It was found that under such conditions as heating or boiling in acetic anhydride, cis-1,2,3,4-CHDA could be converted to its trans-isomer. The process of thermal isomerization was monitored by H-1 NMR spectra and the mechanism of conversion was proposed. Their absolute structures of cis- and trans-1,2,3,4-CHDAs were elucidated by single crystal X-ray diffraction. The polycondensations of cis- and trans-1,2,3,4-CHDAs with aromatic diamines such as 4,4'-oxydianiline (ODA), 4,4'-methylenedianiline (MDA), 4,4'-diamino-3,3'-dimethyldiphenylmethane (DMMDA), 4,4'-bis(4-aminophenoxy)benzene (TPEQ), 2,2-bis[4-(4-aminophenoxy)phenyl] propane (BAPP) were studied. It is easy to obtain higher molecular weight polyimides from trans-1,2,3,4-CHDA using conventional one-step or two-step methods. However, higher molecular weight polyimides derived from cis-1,2,3,4-CHDA could not be prepared by the usual methods (solid content ca. 10%) owing to the trend of forming cyclic oligomers.

A modified Wittig polycondensation - to high-trans- and high-molecular weight PPVs

A modified Wittig polycondensation was developed by replacing the bulky -PPh3 with -PBu3 ylide. Our studies suggested that the modified polymerization dramatically enhances trans-selectivity due to the decreased 1.3-steric interaction between butyl chain and triphenylamine group, together with the 1,2-steric interaction between the phenyl ring of the ylide and the triphenylamine group of the aldehyde. Moreover, the method also enhances high-molecular weight products by increasing the activity and solubility of the ylide.