Chloro(η-dihydropentalenyl)bis(triphenylphosphine)ruthenium(II): synthesis, structural characterization and catalytic activity in the dimerization of phenylacetylene

Reactions between HRuCl(PPh₃)₃ and 1,3- or 1,5-cyclooctadiene yield the 1,2-dihydropentalenyl complex (η⁵-C₈H₉)Ru(PPh₃)₂Cl through a series of steps including olefin insertion and electrocyclization. The reaction is accompanied by the loss of two equivalents of hydrogen. The product crystallizes in the monoclinic space group (No. 2). (η⁵-C₈H₉)Ru(PPh₃)₂Cl catalyzes the dimerization of phenylacetylene to a ≈2:1 mixture of Z:E 1,4-diphenyl-1-buten-3-yne. Comparison of the catalytic activity of (η⁵-C₈H₉)Ru(PPh₃)₂Cl with (η⁵-C₅H₅)Ru(PPh₃)₂Cl, (η⁵-C₅Me₅)Ru(PPh₃)H₃ and {η⁵-HB(pz)₃}Ru(PPh₃)₂Cl suggests that the more electron-rich η⁵ ligands favor formation of the Z isomer.     

Dimerization and Oligomerization of Ethylene Catalyzed by a Palladium(II) Complex with Imine‐phosphine Ligand

The palladium‐iminophosphine complex [Pd(P‐N)(CH₃)Cl] (P‐N = o‐diphenyl‐phosphino‐N‐benzaldimine) has been found to be a catalyst for dimerization and trimerization of ethylene. Some mechanistic insight concerning this oligomerization is discussed.     

Titanium atoms dimerization phenomenon and magnetic properties of titanium-antisite (TiO) and chromium doped rutile TiO2, ab-initio calculation

The ab-initio calculations based on the Korringa Kohn Rostoker approximation approach combined with coherent potential approximation (KKR-CPA), were used to study the magnetic properties of the titanium anti-site (Ti_O) and chromium (Cr) doped TiO₂. In the considered systems, we used different concentrations for Ti_O defect and Cr doping. In TiO_2(0.98)(Ti_O)_0.02, the obtained results indicate that Ti_O is a donor having half-metal behavior. Ti_O[3d] band is located at the Fermi level, although isn’t 100% polarized, the ferromagnetic (FM) state is verified as being more stable than disordered local moment (DLM) state. For Ti_0.98Cr_0.02O₂ the Cr doping introduced new states which give the material half-metallic feature. The majority spin of Cr impurities are located at the Fermi level and the conduction electrons around the Fermi level are 100% spin polarized. This indicates the stability of (FM) state. Moreover, in Ti_0.98Cr_0.02O_2(0.98)(Ti_O)_0.02, the top of the valence band is shifted to lower energy compared to pure TiO₂, and the n-type of TiO₂ is verified. The majority spin of Cr[3d] are located at 0.025 Ry close to the Fermi level. The predicted Curie temperatures (Tc) were calculated using the mean field approximation (MFA) and we predicted that Ti_O defect in Cr doped TiO₂ makes Tc higher. This kind of defect makes the material useful for spinotronics's applications and devices.     

Hydroxy-rhodium(I) catalyzed regioselective Michael addition of cyclic enones

Hydroxy-rhodium catalyzed dimerization of various cyclic enones to the corresponding α-enone adducts is developed. The key feature of this method is that the base-sensitive, highly substituted enones also undergo dimerization and the resultant products are obtained in moderate to good yields.     

0- and 2/3-magnetization plateaus in three-leg antiferromagnetic Heisenberg spin-1/2 ladders with leg-dimerization

Magnetic properties of three-leg antiferromagnetic Heisenberg spin-1/2 ladders with different dimerization patterns have been studied using the bond mean-field theory. Our results show that rung-columnar ladders are thermodynamically stable states for large rung-to-leg coupling ratios. Magnetization curves of leg-columnar and leg-staggered ladders always exhibit 0- and 2/3-magnetization plateaus, which do not appear in rung-columnar and rung-staggered ladders. In leg-dimerized ladders, the formation of spin dimers in the three legs results in the appearance of the 0- and 2/3-magnetization plateaus. Spin configuration in the 2/3-magnetization plateau can be understood from the mean-field bond parameters.     

Monomeric and dimeric red/NIR-fluorescent dipyrrin–germanium complexes: facile monomer–dimer interconversion driven by acid/base additions

Highly coordinate germanium complexes of the N2O2-type tetradentate dipyrrin ligand have been synthesized. X-ray crystallographic analysis revealed the pentacoordinate structure of dimeric germanium complex 2 (=(Ge)₂O) and the hexacoordinate structure of monomeric complex 3 (=Ge(OMe)(HOMe)). The dimer 2 was easily hydrolyzed in a solution to give monomer 4, though the corresponding siloxane (Si)₂O did not react under the same conditions. The addition of DBU to a solution of 4 gave dimer 5, and neutralization by adding acetic acid regenerated the monomer 4, providing the facile and reversible interconversion between the monomer and dimer. The dipyrrin germanium complexes showed an intense absorption and fluorescence near the NIR region, which is more red-shifted than the silicon complexes.     

A new method for generation of non-stabilized α-amino-substituted carbanions by the reaction of magnesium carbenoids with N-lithio arylamines: their reactivity and a new synthesis of α-amino acid derivatives

Magnesium carbenoids were generated from aryl 1-chloroalkyl sulfoxides with i-PrMgCl in THF at low temperature in quantitative yields. The magnesium carbenoids were found to be reactive with N-lithio alkylamines to afford an olefin, which was derived from dimerization of the magnesium carbenoid, in moderate yield. On the other hand, reaction of the magnesium carbenoids with N-substituted N-lithio arylamines gave non-stabilized α-amino-substituted carbanions in good yields. Reactivity of the α-amino-substituted carbanions with some electrophiles was investigated and it was found that ethyl chloroformate reacted to give α-amino acid derivatives in good yields. As a whole, a new method for one-pot, three-component combined synthesis of α-amino acid derivatives from aryl 1-chloroalkyl sulfoxides was realized.     

Supported Metal Sulfate Catalysts FexZny/SiO2 for Selective Dimerization of Isobutene in Mixed C4 to Isooctenes

Isobutene dimerization is an important route to properly utilize mixed C₄ and further produce isooctane with a high-octane number to replace MTBE in gasoline. A highly selective catalyst, which is effective for isobutene dimerization but ineffective for other olefins in the C₄ mixture, is necessary for industrial implementation. In this work, a series of supported metal sulfate catalysts Fe_xZn_y/SiO₂ were prepared and characterized by XRD, SEM, N₂ physical adsorption-desorption, NH₃-TPD, Py-FTIR, and XPS. Fe_0.2Zn_1.8/SiO₂ can achieve isobutene conversion up to 89 % with 0 % conversion of n-butene, and the selectivity of isooctenes (C₈⁼) product is 57 % (10 h on stream). Furthermore, isobutene conversion can sustain above 80 % after 50 h. It is found that these supported catalysts contain Zn²⁺, Zn⁺, Fe³⁺, and Fe²⁺ species, and there is a synergetic effect between Zn²⁺ and Fe²⁺. Zn²⁺ is beneficial to improve the conversion of isobutene, and Fe²⁺ facilitates the formation of C₈⁼, resulting in a high C₈⁼ yield.     

Mammalian ATPsynthase monomer versus dimer profiled by blue native PAGE and activity stain

Studies into the effects of oligomerization on F(0)F(1)ATPsynthase function are contradictory. We optimized the in-gel ATPase assay to investigate the functional differences of monomers versus dimers. In Triton X-100 extracts of heavy bovine heart mitochondria (HBHM) and mitoplasts, but not submitochondrial particles (MgATP-SMP), dimers had greater specific activity than monomers: at 30 degrees C, the dimer/monomer activity ratios were 2.3, 1.4, and 1.0, respectively. These differences in HBHM and mitoplasts extracts were enhanced at 37 degrees C but lost at 20 degrees C. In mitoplasts but not in MgATP-SMP, dimers were selectively shielded from limited chymotrypsin degradation of F(1) alpha subunit, possibly due to interactions with other proteins or ligands in the native inner membrane. Despite these differences, all three preparations had similar percentages of dimers and similar contents of the native inhibitor IF(1) in Vm (monomer) and (dimer) Vd. These results suggest that, in native membrane, monomers and dimers are functionally distinct.     

Manganese triacetate oxidation of methyl 1-hydroxy-2-naphthalene carboxylates

Manganese-triacetate mediated oxidation of 1-hydroxy-2-napthalene carboxylates in benzene under anhydrous conditions delivers the dimerized product. However, acetoxylation on the ortho- or para-position, or oxidation to quinones occurs on the 1-hydroxy-3-substituted 2-napthalene carboxylates depending on the nature of the substituents when the reaction is carried out in a mixture of acetic acid/acetonitrile.