五配位铁硫化合物(Et4N)4〔Fe2(S,X-C6H4-o)4〕的合成与晶体结构

利用无水FeCl与双齿配体Na_2BDT或Na_2MP(Na_2S,X-C,H_4-o_2:X=S,BDT;X=O,MP)在乙醇溶液中反应,然后加入沉淀剂Et_4NBr,可以得到双核铁硫化合物(Et_4N)_2[Fe_(S,X-CH_4-o)_4](1,X=S;2,X=0)。它们分别具有以双硫或双氧桥联起来的五配位扭曲三角双锥构型的铁原子。分子为心对称,核心Fe_2X_2~(2+)为平面。每个铁原子上的二个苯环平面A和B相互近于平行(1,二面角10.1°)或近于垂直(2,二面角100.2°);但铁原子与XSCC平面非共面。Fe原子离平面0.05～0.5A。2是第一个以双齿配位的双氧桥铁硫化合物,它既含有桥基氧原子又具有端基氧原子,对研究含氧配位的铁原子周围环境,为模拟固氧酶中的“P簇”,有一定意义。     

Effect of temperature on the enantioselectivity in the oxazaborolidine-catalyzed asymmetric reduction of ketones. Noncatalytic borane reduction, a nonneglectable factor in the reduction system

The effect of temperature on the enantioselectivity of the oxazaborolidine-catalyzed asymmetric borane reduction of ketones has been investigated carefully using alkyl aryl ketones with a variety of functional groups and a B-methoxyoxazaborolidine derived from trimethyl borate and (S)-alpha,alpha-diphenylprolinol as a catalyst. The reductions were carried out over a range of temperatures in THF and toluene with or without the catalyst. The reductive rates increase along with increasing reaction temperature with or without the catalyst by determining the conversion of the ketones to alcohols by GC analysis. However, the rates of the catalytic reductions increase faster than those without the catalyst. The results indicate that the noncatalytic borane reduction is an important factor to the enantioselectivity in the reduction. The highest enantioselectivities were usually obtained between 20 and 30 degrees C in the asymmetric reduction.     

乙二醇二甲醚三苯基氧化膦三氯合铬Cr[(CH3OCH2CH2OCH3)(OPPh3)Cl3]的合成和晶体结构

标题配合物由Cr(CO)₆和PPh₃在50ml乙二醇二甲醚中回流5小时后过滤,在滤液中加S₂Cl₂,静置后得配合物单晶。晶体属单斜晶系,空间群为P2₁,单胞参数a=9.062(3)Å,b=11.088(3)Å,c=12.153(3)Å,β=97.93(1)°,V=1209.4(1.8)ų,Z=2。 晶体结构是采用Patterson法和差Fourier合成解出。经全矩阵最小2乘法修正,最后偏离因子R=0.046,R_ω=0.054,结构中Cr各与三个氧和三个氯原子键联,Cr-O(CH₃OCH₂CH₂OCH₃)平均距离为2.091Å,Cr-O(OPPh₃)距离为2.000Å,Cr-Cl(平均)距离为2.274Å。它们形成了八面体配位构型。     

山竹的微量元素含量分析

用电感耦合等离子体发射光谱仪(ICP-AES)测定了市售进口越南山竹中微量元素的含量,发现其磷、硫、镁、钙、锌等元素的含量比较丰富,并讨论了这些有益元素与人体健康的关系。     

双齿配体八配位镧系配合物的结构化学研究——La[(S2CNC4H8)3·C4H8O·H2O]的合成和晶体结构

镧的配合物La[(S_2CNC_4H_8)_3·C_4H_8O·H_2O]是由LaCl_3和Na(S_2CNC_4H_8)·2H_2O在四氢呋喃中反应而获得的。它的晶体属于三斜晶系,空间群为Pi,单胞参数a=10.557(2)(?),b=10.943(3)(?),c=13.443(3)(?),α=101.83(2)(?),β=9306(2)°,γ=114.90(2)°,V=1391.9(1.5)(?)~3,Z=2。 晶体结构是采用Patterson法和几轮的差Fourier合成解出的。所有非氢原子的位置参数和各向异性热振动参数经全矩阵最小二乘法修正,最后偏离因子R=0.032,R_w=0.046。分子结构中La原子同三个(S_2CNC_4H_8)~-中的六个S原子和分别来自四氢呋喃分子和水分子中的二个O原子键联。La—S平均距离2.973(?),La—O距离分别为2.596(?)(THF)和2.555(?)(H_2O),它们形成一个扭变三角形十二面体的配位多面体构型。     

Rationale on the Abnormal Effect of Temperature on the Enantioselectivity in the Asymmetric Borane Reduction of Ketones Catalyzed by L‐Prolinol

The effect of temperature on the enantioselectivity of the oxazaborolidine‐catalyzed asymmetric borane reduction of ketones was investigated in the presence of (5S)‐3‐oxa‐1‐aza‐2‐borabicyclo[3.3.0]octane (=(3aS)‐tetrahydro‐1H,3H‐pyrolo[1,2‐c][1,3,2]oxazaborole; 1a ) and its 2‐methoxy derivative ( 1b ) as catalysts, which were synthesized from L ‐prolinol with borane and trimethyl borate, respectively. The results indicate that the two catalysts induce a different temperature‐dependent enantioselectivity. The enantioselectivity of the B‐unsubstituted (5S)‐3‐oxa‐1‐aza‐borabicyclo[3.3.0]octane ( 1a ) increases with increasing temperature, while its B‐methoxy‐substituted derivative 1b shows the highest enantioselectivity at ca. 50°. (5S)‐3‐Oxa‐1‐aza‐2‐borabicyclo[3.3.0]octane ( 1a ) is more likely to dimerize than its 2‐methoxy derivative 1b . The conversion rates of L ‐proline to L ‐prolinol in the presence of different amounts of borane were also determined in this study.     

Controlling the Localization of Liquid Droplets in Polymer Matrices by Evaporative Lithography

Localized inclusions of liquids provide solid materials with many functions, such as self‐healing, secretion, and tunable mechanical properties, in a spatially controlled mode. However, a strategy to control the distribution of liquid droplets in solid matrices directly obtained from a homogeneous solution has not been reported thus far. Herein, we describe an approach to selectively localize liquid droplets in a supramolecular gel directly obtained from its solution by using evaporative lithography. In this process, the formation of droplet‐embedded domains occurs in regions of free evaporation where the non‐volatile liquid is concentrated and undergoes a phase separation to create liquid droplets prior to gelation, while a homogeneous gel matrix is formed in the regions of hindered evaporation. The different regions of a coating with droplet embedment patterns display different secretion abilities, enabling the control of the directional movement of water droplets.