Crystallographic evidence for a free silylium ion

Evidence for a three-coordinate silyl cation is provided by the crystal structure of [(Mes)3Si][H-CB11Me5Br6].C6H6 (where Mes is 2,4,6-trimethylphenyl). Free (Mes)3Si+ cations are well separated from the carborane anions and benzene solvate molecules. Ortho-methyl groups of the mesityl substituents shield the silicon atom from the close approach of nucleophiles, while remaining innocent as significant ligands themselves. The silicon center is three-coordinate and planar. The downfield 29Si nuclear magnetic resonance chemical shift in the solid state (226.7 parts per million) is almost identical to that in benzene solution and in "gas phase" calculations, indicating that three-coordination can be preserved in all phases.     

Crystal structure of a silyl cation with no coordination to anion and distant coordination to solvent

The crystal structure of a stable silyl cation, triethylsilylium, in the form of its tetrakis (pentafluorophenyl)borate salt [Et(3)Si(+) (C(6)F(5))(4)B(-)] (Et, ethyl) shows no coordination between cation and anion. The closest silicon-fluorine distance is greater than 4 angstroms. A toluene solvent molecule is close enough to cause some deviations from planarity at the silicon, but the silicon-toluene distance is well beyond the sum of the silicon and carbon covalent radii. The toluene molecule is essentially planar and undistorted, as expected if little or no positive charge has been transferred from silicon to toluene.     

Decamethyldizincocene, a stable compound of Zn(I) with a Zn-Zn bond

Unlike mercury, which has an extensive +1 oxidation state chemistry, zinc usually adopts the +2 oxidation state. Decamethyldizincocene, Zn2(eta5-C5Me5)2, an organometallic compound of Zn(I) formally derived from the dimetallic [Zn-Zn]2+ unit, has been isolated from the low-temperature (-10 degrees C) reaction of Zn(C5Me5)2 and Zn(C2H5)2 in diethyl ether. X-ray studies show that it contains two eclipsed Zn(eta5-C5Me5) fragments with a Zn-Zn distance (+/- standard deviation) of 2.305(+/-3) angstroms, indicative of a metal-metal bonding interaction.     

Reversible, metal-free hydrogen activation

Although reversible covalent activation of molecular hydrogen (H2) is a common reaction at transition metal centers, it has proven elusive in compounds of the lighter elements. We report that the compound (C6H2Me3)2PH(C6F4)BH(C6F5)2 (Me, methyl), which we derived through an unusual reaction involving dimesitylphosphine substitution at a para carbon of tris(pentafluorophenyl) borane, cleanly loses H2 at temperatures above 100 degrees C. Preliminary kinetic studies reveal this process to be first order. Remarkably, the dehydrogenated product (C6H2Me3)2P(C6F4)B(C6F5)2 is stable and reacts with 1 atmosphere of H2 at 25 degrees C to reform the starting complex. Deuteration studies were also carried out to probe the mechanism.     

Thermal, catalytic, regiospecific functionalization of alkanes

The formation of a single product from terminal functionalization of linear alkanes from a transition metal-catalyzed reaction is reported. The rhodium complex Cp*Rh(eta(4)-C(6)Me(6)) (Cp*, C(5)Me(5); Me, methyl) catalyzes the high-yield formation of linear alkylboranes from commercially available borane reagents under thermal conditions. These reactions now allow catalytic, regiospecific functionalization of alkanes under thermal conditions. The organoborane products are among the most versatile synthetic intermediates in chemistry and serve as convenient precursors to alcohols, amines, and other common classes of functionalized molecules.     

Bimetallic system for nitrogen fixation: ruthenium-assisted protonation of coordinated N2 on tungsten with H2

Treatment of the tungsten dinitrogen complex cis-[W(N2)2(PMe2Ph)4] (Me = methyl, Ph = phenyl) with an equilibrium mixture of [RuCl(dppp)2]X and trans-[RuCl(eta2-H2)(dppp)2]X [X = BF4, PF6, or OSO2CF3; dppp = 1,3-bis(diphenylphosphino)propane] under 1 atmosphere of dihydrogen at 55 degrees Celsius for 24 hours gave NH3 in moderate yield. The same reaction in the presence of acetone produced acetone azine in high yield. None of these reactions proceeded in the absence of dihydrogen.     

Synthesis of inorganic fullerene-like molecules

The reaction of [Cp*Fe(eta5-P5)] with Cu(I)Cl in solvent mixtures of CH2Cl2/CH3CN leads to the formation of entirely inorganic fullerene-like molecules of the formula [[Cp*Fe(eta5:eta1:eta1:eta1:eta1:eta1-P5)]12[CuCl]10[Cu2Cl3]5[Cu(CH3CN)2]5] (1) possessing 90 inorganic core atoms. This compound represents a structural motif similar to that of C60: cyclo-P5 rings of [Cp*Fe(eta5-P5)] molecules are surrounded by six-membered P4Cu2 rings that result from the coordination of each of the phosphorus lone pairs to CuCl metal centers, which are further coordinated by P atoms of other cyclo-P5 rings. Thus, five- and six-membered rings alternate in a manner comparable to that observed in the fullerene molecules. The so-formed half shells are joined by [Cu2Cl3]- as well as by [Cu(CH3CN)2]+ units. The spherical body has an inside diameter of 1.25 nanometers and an outside diameter of 2.13 nanometers, which is about three times as large as that of C60.     

A stable silicon(0) compound with a Si=Si double bond

Dative, or nonoxidative, ligand coordination is common in transition metal complexes; however, this bonding motif is rare in compounds of main group elements in the formal oxidation state of zero. Here, we report that the potassium graphite reduction of the neutral hypervalent silicon-carbene complex L:SiCl4 {where L: is:C[N(2,6-Pri2-C6H3)CH]2 and Pri is isopropyl} produces L:(Cl)Si-Si(Cl):L, a carbene-stabilized bis-silylene, and L:Si=Si:L, a carbene-stabilized diatomic silicon molecule with the Si atoms in the formal oxidation state of zero. The Si-Si bond distance of 2.2294 +/- 0.0011 (standard deviation) angstroms in L:Si=Si:L is consistent with a Si=Si double bond. Complementary computational studies confirm the nature of the bonding in L:(Cl)Si-Si(Cl):L and L:Si=Si:L.     

Eclogitic pyroxenes, ordered with p2 symmetry

X-ray diffraction crystal-structure analysis of omphacite from eclogite, Tiburon Peninsula, Marin County, California, shows that this clinopyroxene has P2 symmetry with a nearly ordered distribution of the multiple cation content defined by its approximate formula: (Na(o.5) Ca(o.5)) (Mg(o.4)Fe(2)+( 0.1) Al(0.4) Fe(3) +(0.1)) Si(2)0(6). Na+ and Ca(2+) tend to assume alternate locations in the structure, and ( Mg,Fe(2+)) octahedra alternate with Al(3+). or (Al,F(3+)) octahedra in chains along c.     

EDTA-乙酸铵浸提ICP-OES法直接测定土壤中的交换性钾钠钙镁锰

[目的]土壤交换性能可以用来评价土壤的保肥供肥能力,研究土壤中交换性阳离子为改良土壤和合理施肥提供重要依据。[方法]采用0.005mol/LEDTA-乙酸铵混合溶液作为交换提取剂,与土壤中的Ca2＋、Mg2＋、Mn2＋、Na＋、K＋等阳离子进行交换,浸取液干过滤后使用电感耦合等离子体光谱仪（ICP-OES）直接测定土壤中多种交换性阳离子。[结果]该方法的钙（Ca）、镁（Mg）、钾（K）、钠（Na）和锰（Mn）检出限分别为：0.1500、0.0075、0.2500、0.0640、0.0010μg/ml。该方法快速、简便。标准物质ASA-1a,ASA-4a,ASA-5a,ASA-6a,ASA-7测定钙、镁、钾、钠和锰的相对误差（RE）分别为0.62%～7.50%,2.22%～9.52%,1.59%～4.88%,2.98%～10.00%和3.23%～9.38%。5次测定ASA-1a测定结果的RSD分别为：1.69%、1.58%、1.33%、5.80%、4.20%,ASA-6a测定结果的RSD分别为：3.20%、2.21%、2.89%、2.25%、7.87%。[结论]分析结果符合《DD2005-03生态地球化学评价样品分析技术要求》,为土壤阳离子交换性阳离子的简便快速测定提供新的试验方法。     

Closely Approaching the Silylium Ion (R3Si+)

The crystal structure of the tri-isopropyl silyl species, i-Pr(3)Si(Br(6)-CB(11)H(6)), where the brominated carborane Br(6)-CB(11) H(6)(-) is perhaps the least nucleophilic anion presently known, has revealed the highest degree of silylium cation character (R(3)Si(+)) yet observed. The average C-Si-C angle is 117 degrees , only 3 degrees short of the planarity expected of a pure silylium ion(120 degrees ). This value compares to 114 degrees recently reported for a toluene-solvated silyl cation, [Et(3)Si(toluene)](+) by Lambert and co-workers. The greater silylium ion character of i-Pr(3)Si(Br(6)-CB(11)H(6)) versus [i-Pr(3)Si(toluene)](+) is also reflected in the larger downfield shift of the silicon-29 nuclear magnetic resonance, 109.8 versus 相似文献   

把烟快速定级等级错误率及错误去向分析

[目的]突破烟叶评级高技能人才在把烟快速定级中的技术瓶颈。[方法]以智能化烟叶分级实训考核系统为数据来源,采用统计学分析法,首次将烤烟42等级在把烟快速定级考试中的出现频率、等级错误率及错误去向进行了量化分析。[结果]等级B2F与B3F、B2R与B3R、C3F和C4F、C3L和C4L这4组等级互为易错,属于易混淆等级;等级X1F、X1L和X2F的错误去向分别为C3F(20.1%)、C3L(35.7%)和C4F(16.5%),属于部位易错等级;X2L和X4L的错误去向分别为X2F(15.8%)和X4F(13.8%),属于颜色易错等级;等级B1L、B2L、C2F、C4F、C2L、X1F、C3V和CX1K的易错等级均为C3F,即C3F是热点等级。[结论]研究结果为有针对性地提升把烟快速定级技能水平提供理论依据。     

单叶快速定级等级错误去向量化分析

[目的]突破烟叶分级技术能力提升的瓶颈。[方法]采用统计分析法,对单叶快速定级的等级错误率及错误去向进行量化分析。[结果]等级错误率以B1L最高,达到79.6%,其次为等级X1F(66.2%)、B1F(63.9%)、X1L(62.1%)和C4L(60.2%)。等级X2F、X2L,B2L和C4L的错误去向分别为C3F(8.1%)、C3L(9.3%)、C2F(10.8%)和X2L(15.9%),属于部位易错等级;等级X3L和X4L的错误去向分别为X3F(12.1%)和X4F(19.6%),属于颜色易错等级。其中,等级B3F与B4F、B3L与B4L、C2F与C3F、C2L与C3L、X3F与X4F、B2K与B3K、GY1与GY2这7组等级互为易错,属于易混淆等级。[结论]该研究可为找准单叶快速定级疑难点提供数据支撑。     

抗犬细小病毒的单克隆抗体的制备

CPV YZ株的细胞培养液经蔗糖密度梯度离心纯化后作为免疫原免疫BALB/C小鼠 ,应用杂交瘤技术筛选出 8株能稳定分泌单克隆抗体的杂交瘤细胞 ,分别命名为F5G10、3F11F4、F11G6、6C5C2、6E4G3、6C2B11、F11D6、3D9C4株 ,各株单抗均为IgG型 ;中和试验表明 :F11G6、3D9C4、6E4G3、6C5B114株单抗有中和作用 ,Dot ELISA试验证明了 8株单抗仅针对病毒抗原决定簇的空间结构。     

重组捻转血矛线虫半乳糖结合凝集素免疫山羊皱胃细胞因子表达定位

【目的】检测重组雌、雄捻转血矛线虫半乳糖结合凝集素(rHco-GAL-f/m)免疫山羊皱胃转录细胞因子。【方法】用rHco-GAL-f/m免疫山羊,通过原位杂交法对阴性对照组(A)、攻虫对照组(B)、免疫攻虫组(C)和免疫不攻虫组(D)山羊皱胃中白介素-1β(IL-1β)、白介素-2(IL-2)、白介素-4(IL-4)、白介素-6(IL-6)、干扰素-γ(IFN-γ)和肿瘤坏死因子-α(TNF-α)mRNA转录进行定位,并对上述细胞因子阳性反应细胞数量进行分析。【结果】A组山羊皱胃组织中没有检测到细胞因子,其它3组仅在皱胃黏膜下层中检测到了上述细胞因子。B、C和D组间IL-4和IL-6阳性反应细胞数差异显著(P0.05),其中C组明显高于其它两组;B、C和D组间IL-1?、IL-2和TNF-α阳性反应细胞数差异显著(P0.05),其中D组明显高于其它两组;IFN-γ阳性反应细胞数在B组和C组之间差异不显著(P0.05),D组与B组和C组之间差异显著(P0.05),且明显高于其它两组。【结论】重组捻转血矛线虫半乳糖结合凝集素能够诱导山羊皱胃局部免疫应答。     

硅磷优化施肥模式对广西赤红壤甘蔗产量和品质的影响

[目的]研究硅磷优化施肥模式对广西赤红壤甘蔗产量和品质的影响,为建立广西甘蔗生态高值栽培技术提供科学依据。[方法]采取二次回归D一最优设计在广西隆安蔗地进行甘蔗田间试验,运用SAS统计分析软件对试验结果进行回归分析,建立多项式回归模型,并通过计算机程序对模型进行仿真寻优,寻求适合甘蔗营养模式的最佳硅磷配比。[结果]在该试验条件下,施磷及硅磷配施有利于甘蔗分蘖和生长,有较多的有效茎,并可获得较高的甘蔗产量和较优的品质。用SAS统计分析软件进行分析,得甘蔗产量（1,）、蔗糖产量（SY）与磷素（x,）、硅素（x：）之间的回归模型：Y=110096．92＋4356．91X1。＋2007．65X2-1592．35X1X2-5461．33X（^2,1）-7442．09X（^2,2）,R=0．914;SY=16471．85＋903．65X1,＋424．26X2-99．02X1X2。X2-1170．O8X（^2,1）-l 256．96X（^2,2）,R=0．930;该试验所建立的甘蔗产量和蔗糖产量回归数学模型与当地实际情况拟合较好,具有较强的实用性,可用作当地甘蔗施肥决策和预报。采用计算机进行寻优,分别得到甘蔗产量和蔗糖产量最佳的营养模式,即当磷硅肥用量分别为281．3kg（P205）／hm^＋。和405．0kg（SiO2）／hm2。（P2O5：SiO2=1：1．44）时,得到最佳蔗茎产量和蔗糖产量,分别为109 405．6和16682．3kg／hm2。。[结论]适合于广西赤红壤区土壤条件的甘蔗硅磷最佳组合方案281．3kg（P205）／hm2。和405．0kg（SiO2：）／hm2。（P205：SiO2：=1：1．44）。     

黄腐酸钾定位施肥对棉花产量及品质性状的影响

[目的]为提高棉花产量、品质,研究黄腐酸钾的最佳用量。[方法]采用大田随机区组定位试验,设置6个处理,CK:不施肥,F:单施化肥750 kg/hm~2,F+H1:化肥750 kg/hm~2配施黄腐酸钾75 kg/hm~2,F+H2:化肥750 kg/hm~2配施黄腐酸钾150 kg/hm~2,F+H3:化肥750 kg/hm~2配施黄腐酸钾300 kg/hm~2,F+H4:化肥750 kg/hm~2配施黄腐酸钾450 kg/hm~2,定位4年后测定棉花株高、果枝数、成铃数、单铃重、衣分、籽棉产量、纤维品质等指标。[结果]化肥与黄腐酸钾配施能促进棉花后期的营养生长与生殖生长,随着黄腐酸钾用量增加秋桃数与秋桃比例呈增加趋势;单株铃数、籽棉产量、皮棉产量呈随黄腐酸钾用量增加而增加的趋势,4个配施黄腐酸钾处理较单施化肥处理籽棉产量分别提高3.3%、5.4%、5.2%与9.0%;配施黄腐酸钾提高了棉花纤维品质,尤其是对纺纱均匀性指数有显著提升作用。[结论]化肥配合施用黄腐酸钾450 kg/hm~2,可有效提高棉花产量,改善棉花纤维品质。     

HPLC法检测复合维生素片中叶酸和维生素B_(12)的含量

[目的]建立应用高效液相法测定复合维生素片中叶酸和维生素B12含量的方法。[方法]色谱柱用菲罗门lunaC18(4.6×250 mm,5μm),流动相为甲醇-0.028 mol/L磷酸氢二钠水溶液(用磷酸调pH到3.5)(21∶79),流速1.0 ml/min,检测波长为361 nm,进样量为20μl,柱温为25℃。[结果]维生素B12在6.65～66.50 ng范围内呈现良好的线性关系,回归方程是y=0.495 1x+1.342 8(R2=0.999 4,n=6),平均回收率为96.83%,RSD为0.82%(n=6)。叶酸在80～800 ng范围内呈现良好的线性关系,回归方程是y=0.021 1 x+0.661 1(R2=0.998 8,n=6),平均回收率为95.56%,RSD为1.54%(n=6)。[结论]高效液相色谱法灵敏度高,操作简便,重现性好,结果准确,可以用于复合维生素片中叶酸和维生素B12的含量测定。     

B原子浓度对非晶态Ni—Si—B系合金电阻应变系数的影响

通过Ｎｉ－Ｓｉ－Ｂ系非晶合金电阻随拉应变变化特性曲线的测定，考察了Ｂ原子浓度对非晶Ｎｉ７２－ｘＳｉ１５Ｂ１３＋ｘ（ｘ＝０，２，４，６，８）合金电阻应变系数的影响，并采用Ｎａｇｅｌ推广的液态金属Ｚｉｍａｎ理论对其实验结果进行了初步的解释．     

山茶属5种植物的核型研究

 本文报道了山茶属5种植物的核型:1.矩叶茶Camellia grijsii Hance核型公式为2n=2x=30=20m+7sm+3st;2.文山毛蕊茶C.wenshanensis Hu核型公式为2n=2x=30=20m+8sm+2st;3.紫果茶C.purpura Chang et Chen核型公式为2n=2x=30=22m+4sm+4st;4.显脉金花茶C.euphelebia Merr.ex Sealy核型公式为2n=2x=30=21m(4sat)+9sm(2sat);5.五柱滇山茶C.yunnanensis(Pitard ex Diels)Cohen Stuart核型公式为2n=2x=30=26m(2sat)+4sm.这5种植物分属不同的亚属及组.结果表明它们均是二倍体2n=30,但核型结构明显不同.核型类型前2种属2A型,后3种属2B型.