Synthesis, Characterization, Crystal Structure and Stability of a Ternary Cu（Ⅱ） complex with 1, 10-Phenanthroline and L-Valinate

It is important to research the mixed-ligand copper complexes containing bioligands, such as amino acids, nucleic acids and proteins, in exploring the functional mechanism of microelement copper in organism because the reaction of any micronutrient with two or more bioligands in the concentrated bioligands background gives mixed-ligand ternary complexes, which are more stable and related with storage of substance and transportationof metal ions in the life process.     

以空气为氧化剂Pd(OAc)2/HPMo/AcOH催化苯液相氧化偶联合成联苯

 研究了以Pd(OAc)2为催化剂,H3PMo12O40为助催化剂,空气为氧化剂,在乙酸溶液中于373 K条件下,在500 ml高压釜中由苯液相氧化偶联合成联苯. 结果表明,反应产物中联苯的选择性高达92%以上,并且只有少量的三联苯副产物生成. 分别考察了H3PMo12O40的加入量和O2分压对以空气或纯O2为氧化剂时Pd/HPMo/AcOH催化苯液相氧化偶联合成联苯反应催化性能的影响. 根据反应液颜色的变化以及文献结果推测,在反应过程中通过钯和钼物种的氧化和还原作用使苯氧化生成联苯.     

Homoleptic Zincate‐Promoted Room‐Temperature Halogen–Metal Exchange of Bromopyridines

Homoleptic lithium tri‐ and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine–metal exchanges were realized at room temperature with a substoichiometric amount of nBu₄ZnLi₂?TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine). This reactivity contrasted with that of tBu₄ZnLi₂?TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N???Li stabilized polypyridyl zincates in the reaction. The one‐pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C? Zn bonds in bromopyridines enabled us to perform efficient Negishi‐type cross‐couplings.     

ACE applied to the quantitative characterization of benzo‐18‐crown‐6‐ether binding with alkali metal ions in a methanol–water solvent system

ACE was applied to the quantitative evaluation of noncovalent binding interactions between benzo‐18‐crown‐6‐ether (B18C6) and several alkali metal ions, Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺, in a mixed binary solvent system, methanol–water (50/50 v/v). The apparent binding (stability) constants (K_b) of B18C6–alkali metal ion complexes in the hydro‐organic medium above were determined from the dependence of the effective electrophoretic mobility of B18C6 on the concentration of alkali metal ions in the BGE using a nonlinear regression analysis. Before regression analysis, the mobilities measured by ACE at ambient temperature and variable ionic strength of the BGE were corrected by a new procedure to the reference temperature, 25°C, and the constant ionic strength, 10 mM . In the 50% v/v methanol–water solvent system, like in pure methanol, B18C6 formed the strongest complex with potassium ion (log K_b=2.89±0.17), the weakest complex with cesium ion (log K_b=2.04±0.20), and no complexation was observed between B18C6 and the lithium ion. In the mixed methanol–water solvent system, the binding constants of the complexes above were found to be about two orders lower than in methanol and about one order higher than in water.     

Polyimide/polyoxometalate copolymer thin films: synthesis,thermal and dielectric properties

A mono‐lancunary keggin‐type decatungstosilicate (SiW₁₁) polyoxometalate (POM) modified by γ‐aminopropyltriethoxysilane (KH550) was incorporated into polyimide (PI) through copolymerization. Nuclear magnetic resonance (NMR), fourier transition infrared spectroscopy (FTIR), and wide angle X‐ray diffraction (WAXD) were used to characterize the structure and composition of the polyoxometalate–organosilane hybrid (SiW₁₁KH550) and PI/SiW₁₁KH550 copolymers. The differential scanning calorimetry (DSC) studies indicate that the glass transition temperature (T_g) of PI/SiW₁₁KH550 copolymers increases from 330°C (for neat PI) to 409°C (for the copolymer sample with 10 wt% of SiW₁₁KH550). Dielectric measurement showed that both the dielectric constant and the dielectric loss for the copolymer thin films decreased with the increase in SiW₁₁KH550 content, and the dielectric constant and dielectric loss values decreased to 2.1 and 3.54 × 10^?3, respectively, for the copolymer sample with 10 wt% of SiW₁₁KH550. The incorporation of SiW₁₁KH550 into polymer matrices is a promising approach to prepare PI films with a low dielectric constant and low dielectric loss. Copyright © 2009 John Wiley & Sons, Ltd.     

Phase‐Controlled Synthesis of Transition‐Metal Phosphide Nanowires by Ullmann‐Type Reactions

Transition‐metal phosphide nanowires were facilely synthesized by Ullmann‐type reactions between transition metals and triphenylphosphine in vacuum‐sealed tubes at 350–400 °C. The phase (stoichiometry) of the phosphide products is controllable by tuning the metal/PPh₃ molar ratio and concentration, reaction temperature and time, and heating rate. Six classes of iron, cobalt, and nickel phosphide (Fe₂P, FeP, Co₂P, CoP, Ni₂P, and NiP₂) nanostructures were prepared to demonstrate the general applicability of this new method. The resulting phosphide nanostructures exhibit interesting phase‐ and composition‐dependent magnetic properties, and magnetic measurements suggested that the Co₂P nanowires with anti‐PbCl₂ structure show a ferromagnetic–paramagnetic transition at 6 K, while the MnP‐structured CoP nanowires are paramagnetic with Curie–Weiss behavior. Moreover, GC‐MS analyses of organic byproducts of the reaction revealed that thermally generated phenyl radicals promoted the formation of transition‐metal phosphides under synthetic conditions. Our work offers a general method for preparing one‐dimensional nanoscale transition‐metal phosphides that are promising for magnetic and electronic applications.     

Direct Synthesis of Titanium Complexes with Chelating cis‐9,10‐Dihydrophenanthrenediamide Ligands through Sequential C?C Bond‐Forming Reactions from o‐Metalated Arylimines

A series of new titanium(IV) complexes with o‐metalated arylimine and/or cis‐9,10‐dihydrophenanthrenediamide ligands, [o‐C₆H₄(CH?NR)TiCl₃] (R=2,6‐iPr₂C₆H₃ ( 3 a ), 2,6‐Me₂C₆H₃ ( 3 b ), tBu ( 3 c )), [cis‐9,10‐PhenH₂(NR)₂TiCl₂] (PhenH₂=9,10‐dihydrophenanthrene; R=2,6‐iPr₂C₆H₃ ( 4 a ), 2,6‐Me₂C₆H₃ ( 4 b ), tBu ( 4 c )), [{cis‐9,10‐PhenH₂(NR)₂}{o‐C₆H₄(HC?NR)}TiCl] (R=2,6‐iPr₂C₆H₃ ( 5 a ), 2,6‐Me₂C₆H₃ ( 5 b ), tBu ( 5 c )), have been synthesised from the reactions of TiCl₄ with o‐C₆H₄(CH?NR)Li (R=2,6‐iPr₂C₆H₃, 2,6‐Me₂C₆H₃, tBu). Complexes 4 and 5 were formed unexpectedly from the reactions of TiCl₄ with two or three equivalents of the corresponding o‐C₆H₄(CH?NR)Li followed by sequential intramolecular C? C bond‐forming reductive elimination and oxidative coupling reactions. Attempts to isolate the intermediates, [{o‐C₆H₄(CH?NR)}₂TiCl₂] ( 2 ), were unsuccessful. All complexes were characterised by ¹H and ¹³C NMR spectroscopy, and the molecular structures of 3 a , 4 a – c , 5 a , and 5 c were determined by X‐ray crystallography.     

Reductive Dimerization of Triruthenium Clusters Containing Cationic Aromatic N‐Heterocyclic Ligands

The cationic cluster complexes [Ru₃(μ‐H)(μ‐κ²N,C‐L¹ Me)(CO)₁₀]⁺ ( 1 ⁺; HL¹ Me=N‐methylpyrazinium), [Ru₃(μ‐H)(μ‐κ²N,C‐L² Me)(CO)₁₀]⁺ ( 2 ⁺; HL² Me=N‐methylquinoxalinium), and [Ru₃(μ‐H)(μ‐κ²‐N,C‐L³ Me)(CO)₁₀]⁺ ( 3 ⁺; HL³ Me=N‐methyl‐1,5‐naphthyridinium), which contain cationic N‐heterocyclic ligands, undergo one‐electron reduction processes to become short lived, ligand‐centered, trinuclear, radical species ( 1 – 3 ) that end in the formation of an intermolecular C? C bond between the ligands of two such radicals, thus leading to neutral hexanuclear derivatives. These dimerization processes are selective, in the sense that they only occur through the exo face of the bridging ligands of trinuclear enantiomers of the same configuration, as they only afford hexanuclear dimers with rac structures (C₂ symmetry). The following are the dimeric products that have been isolated by using cobaltocene as reducing agent: [Ru₆(μ‐H)₂{μ₆‐κ⁴N₂,C₂‐(L¹ Me)₂}(CO)₁₈] ( 5 ; from 1 ⁺), [Ru₆(μ‐H)₂{μ₆‐κ⁴N₂,C₂‐(L² Me)₂}(CO)₁₈] ( 6 ; from 2 ⁺), and [Ru₆(μ‐H)₂{μ₄‐κ⁸N₂,C₆‐(L³ Me)₂}(CO)₁₈] ( 7 ; from 3 ⁺). The structures of the final hexanuclear products depend on the N‐heterocyclic ligand attached to the starting materials. Thus, although both trinuclear subunits of 5 and 6 are face‐capped by their bridging ligands, the coordination mode of the ligand of 5 is different from that of the ligand of 6 . The trinuclear subunits of 7 are edge‐bridged by its bridging ligand. In the presence of moisture, the reduction of 3 ⁺ with cobaltocene also affords a trinuclear derivative, [Ru₃(μ‐H)(μ‐κ²N,C‐L^3′ Me)(CO)₁₀] ( 8 ), whose bridging ligand (L^3′ Me) results from the formal substitution of an oxygen atom for the hydrogen atom (as a proton) that in 3 ⁺ is attached to the C⁶ carbon atom of its heterocyclic ligand. The results have been rationalized with the help of electrochemical measurements and DFT calculations, which have also shed light on the nature of the odd‐electron species, 1 – 3 , and on the regioselectivity of their dimerization processes. It seems that the sort of coupling reactions described herein requires cationic complexes with ligand‐based LUMOs.     

Broken symmetry density functional study of a mixed‐valence unsymmetrical dinuclear iron complex

Density functional theory (DFT) calculations with different exchange‐correlation functionals were performed for a mixed valence Fe(II)/Fe(III) binuclear complex with μ‐methoxo and two μ‐carboxylate bridging ligands, (1) with geometry optimizations being performed for all possible spin multiplicities (M_S = 2, 4, 6, 8, and 10). Within the exchange‐correlation functionals studied, only the hybrid GGA functionals B3P and B3LYP and also the pure GGA functional RPBE, predicts the geometry with high spin (S = 9/2) to be more stable than the geometry with low spin state (S = 1/2) by 20 kcal/mol, in agreement with the experimental findings. These functionals also predict the same stability order for the different spin states, being M_S = 10>8>6>2>4. The meta‐GGA functionals TPSS and TPSSh and also the pure GGA functionals BLYP and BP86 predict different stability orders. The computed average EPR g‐tensor, g_av, of 2.03, at the B3LYP level, is in good agreement with the experimental findings. Heisenberg exchange coupling constants, J, were calculated within the broken‐symmetry formalism, at the B3LYP level, showing that the two iron centers are antiferromagnetic coupling, with a very weak coupling constant of about ?7 cm^?1, in good agreement with the experimental value. Additionally, the effect of using different multiplicities of the reference geometries on the computed J value is discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010