Synthesis and Characterization of Methylzinc Tri(tert‐butyl)silylphosphanide as well as Related Sodium and Potassium Phosphanylzincates

The reaction of dimethylzinc and tri(tert‐butyl)silylphosphane in toluene yielded dimeric methylzinc tri(tert‐butyl)silylphosphanide ( 1 ) which crystallized tetrameric. Compound 1 was deprotonated with sodium in DME and the solvent‐separated dimeric ion pair [(dme)₃Na]⁺ [(dme)Na(MeZn)₂(μ‐PSitBu₃)₂]^? ( 2 ) was isolated. The reaction of 1 in THF with two equivalents of potassium and one equivalent of tri(tert‐butyl)silylphosphane gave dimeric [{tBu₃Si(H)P}{(thf)₂K}₂(MeZn)(PSitBu₃)]₂ ( 3 ). Both of these phosphanylzincates contain Zn₂P₂ cycles with Zn‐P bond lengths of approximately 237 pm, whereas in 1 larger Zn‐P bond lengths of 248.5 pm were found due to the larger coordination numbers of the phosphorus and zinc atoms.     

Affinity capillary electrophoresis study of the linkage existing between proton and zinc ion binding to bacitracin A1

Measurements by capillary electrophoresis (CE) of bacitracin A(1) effective mobility at different pH values permitted to estimate the five acidic dissociation constants and the Stokes radii at different protonation stages of the macrocyclic dodecapeptide. The pK(a) values were 3.6 and 4.4 for the two carboxylic groups of the lateral chains of D-Asp-11 and D-Glu-4, respectively, 6.4 for the aza-atom of the imidazole ring of His-10, 7.6 for the amino group of N-terminal Ile-1 and 9.7 for the delta-amino group of D-Orn-7, very close to the values obtained by other researchers by titration experiments. In agreement with a rigid macrocyclic structure the Stokes radii of different protonated forms ranged only between 14.3 and 14.8 A. Best fitting procedures performed on experimental mobility measured at two different pH values (5.50 and 6.72) in the presence of increasing Zn(+2) concentration allowed confirming the model that assumes the binding of Zn(+2) to P(0) peptide form with a 1.5 x 10(3) M(-1) intrinsic association constant. Following to Zn(+2) binding, the pK(a) of the amino group of N-terminal Ile-1 is shifted from 7.6 to 5.9 and the Stokes radius is reduced of about 3 A. The mean charge of the bacitracin A(1)-Zn(+2) complex resulted +1.67 and +1.12 at pH 5.50 and 6.72, respectively. These results suggest that the amino group of N-terminal Ile-1 is not essential for Zn(+2) binding.     

Mixed-metal flux synthesis of quaternary RMn2TrxZn20−x compounds with Tr=Al, In

Eighteen new intermetallic compounds RMn₂Tr_xZn_20−x (2<x<7; R=rare-earth metal; Tr=Al, In) were synthesized using low-melting mixtures of (Tr/Zn) as a solvent. Structural refinement using single-crystal X-ray diffraction data shows that the compounds are substituted variants of the cubic CeCr₂Al₂₀-type structure (Fd-3m, Z=8; unit cell parameters vary from a=14.1152(3)Å for YbMn₂Al_5.3Zn_14.7 to a=14.8125(4)Å for SmMn₂In_5.9Zn_14.1). The Zn and Tr elements show site preferences in the indium compounds, but not in the aluminum analogs. The substitution of trielide element for zinc modifies the valence electron count of the compounds to allow for the incorporation of Mn into the structure. Magnetic susceptibility data show no evidence of magnetic ordering down to 3 K.     

双波长分光光度法测定湿法炼锌净化液中的痕量锗

选择水杨基荧光酮－乳化剂ＯＰ－盐酸为显色体系，应用双波长分光光度法扣除硫酸锌的基体干扰，不分离直接测定了湿法炼锌过程中硫酸锌净化液中的痕量锗。测定范围在０－４０ｍｇ／Ｌ。本法应用于株洲冶炼厂锌净化液中锗的测定，结果与该厂长期的萃取－比色法结果相吻合，而测定速度较萃取－比色法至少提高了一倍。     

超临界二氧化碳中马来酸锌催化合成环状碳酸酯

在超临界二氧化碳中, 利用马来酸锌催化二氧化碳与环氧化物反应合成环状碳酸酯. 单独使用马来酸锌作为催化剂时, 对二氧化碳与环氧丙烷反应的催化活性较低, 而在DBU、DMAP、三乙胺、吡啶、咪唑或4-氨基吡啶等有机碱的存在下, 反应活性较高, 产物的收率得到明显提高. 有机碱作用的强弱顺序为DBU>Et3N>咪唑>4-氨基吡啶>DMAP>吡啶. 在压力为8 MPa, 温度110 ℃, 反应时间48 h条件下, 马来酸锌与DBU组成的二元催化系统可以催化二氧化碳与环氧丙烷反应, 得到83.4%产率的碳酸丙烯酯. 该二元系统也能催化其它环氧化物高产率地转化为相应的环状碳酸酯.     

α,β,γ,δ-四-(羟基苯)卟吩与锌离子络合物光度特性的研究

为探讨羟基苯卟吩与锌离子络合物的光度特性,对三种新合成的卟啉化合物与锌离子的显色反应分别作了研究和比较。实验表明T-(3-HP)P所生成的络合物的灵敏度最高,其表观摩尔吸光系数达4.76×10~5L·mol~(-1)·cm~(-1)。本文还就试剂的分子结构与显色反应的某些规律作了初步的讨论。     

新显色剂4,4′-二偶氮苯重氮氨基偶氮苯测定水中微量锌的研究

本文报告在四硼酸钠体系中和Triton X-100存在下,锌与新显色剂4,4′-二偶氮苯重氮氨基偶氮苯有灵敏的显色反应。红色络合物在525nm处摩尔吸光系数为1.63×10~5L·mol~(-1)·cm~(-1),并研究了测定锌的各种条件和40余种共存离子对测定的影响。     

Adsorptive Stripping Voltammetric Determination of Ultra Trace of Zinc and Lead with Carbidopa as Complexing Agent in Food and Water Samples

In the present work, the cathodic stripping voltammetric methodology using a hanging mercury drop electrode was described for simultaneous determination of lead and zinc in different real samples. The method is based on adsorption of metal ions on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. Optimal conditions were found to be: accumulation time; 70 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s^?1, supporting electrolyte; 0.01 M ammonia buffer at pH 8.5, and concentration of carbidopa; 8.0 μM. The relationship between the peak current versus concentration was linear over the range of 0.1–210 and 0.2–170 nM for lead and zinc, respectively. The detection limits are 0.09 and 0.15 nM for lead and zinc ions respectively. The relative standard deviations at a concentration level of 70 nM of both metal ions are found 1.08 and 1.24% for lead and zinc ions respectively.     

Solvolthermal Syntheses and Crystal Structures of Three Linear Trinuclear Schiff Base Complexes of Zinc(II) and Cadmium(II)

Three linear trinuclear Schiff base complexes, {Zn[Zn(CH₃COO)(C₁₇H₁₆N₂O₂)]₂} ( 1 ), {Zn[Zn(CH₃COO)(C₂₅H₂₀N₂O₂)]₂} ( 2 ), and {Cd[Cd(CH₃COO)(C₁₈H₁₈N₂O₂)]₂} ( 3 ), were synthesized for the first time under solvolthermal conditions. Their structures have been characterized by elemental analyses, X-ray single crystal determinations, and infrared spectroscopy. There are three bridges across the M-M atom pairs (M is Zn for 1 and 2 , or Cd for 3 ) in each complex, involving two O atoms of a Schiff base ligand (N,N′-bis(salicylidene)-1, 3-propanediaminate (SALPD^2-) for 1 , N, N′-bis(2-hydroxy-naphthalmethenylimino)-1, 3-propanediaminate (NAPTPD^2-) for 2 , and N,N′-bis-(salicylidene)-1,4-butanediaminate (SALBD^2-) for 3 ), and an O-C-O moiety of a μ-acetato group. In each of the complexes, the central M²⁺ ion is located on an inversion center and has a distorted octahedral coordination involving four bridging O atoms from two Schiff base ligands in the equatorial plane and one O atom from each bridging acetate group in the axial positions. The coordination around the terminal M²⁺ ions is irregular square pyramidal, with two O atoms and two N atoms of the Schiff base ligand in the basal plane and one O atom from an acetate group in the apical position. The acetate bridges linking the central and terminal M²⁺ ions are mutually trans. The M…M distances are 3.050(3) Å in 1 , 3.139(2) Å in 2 , and 3.287(6) Å in 3 .     

Preconcentration of lead,cadmium, copper and zinc in water at the pg g−1 level by non-boiling evaporation

An evaluation of the non-boiling evaporation technique for the preconcentration of Pb, Cd, Cu, Zn at the pg g^?1 level in water samples is presented. Various improvements were made to allow efficient control of contamination problems at these extremely low concentrations. They include the choice of FEP Teflon for the evaporation containers and the use of sophisticated cleaning, ageing and pre-conditionning procedures. Detailed calibration graphs were obtained down to the sub-pg g^?1 level by processing ultra-low concentration standards. This technique was then applied to the determination of these four metals in snow samples collected in Greenland and Antarctica.