首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 687 毫秒
1.
《Analytical letters》2012,45(4):449-465
Abstract

Complexation constants of Pb2+ and Cd2+ nitrates with five crown compounds (18-crown-6, dicyclohexyl-18-crown-6, benzo-15-crown-5, dibenzo-24-crown-8 and 12-crown-4), have been determined by d.c. and a.c. polarographic measurements in aqueous medium using 0.1 M HNO3 as supporting electrolyte. The complexes of lead with 18-crown-6 and dicyclohexyl-18-crown-6 are very stable which may be attributed to the partially covalent bonds formed by this metal ion.  相似文献   

2.
Treatment of Ba[N(SiMe3)2]2(THF)2 with 2 equiv of dimethylaminotetrazole or diisopropylaminotetrazole and 1 equiv of 18-crown-6 afforded Ba[CN4(NMe2)]2(18-crown-6) (87%) and Ba[CN4(NiPr2)]2(18-crown-6) (79%) as colorless crystalline solids. Ba[CN4(NMe2)]2(18-crown-6) contains two 1,2-eta2-tetrazolato ligands and one eta6-18-crown-6 ligand. The molecular structure of Ba[CN4(NiPr2)]2(18-crown-6) is similar to that of Ba[CN4(NMe2)]2(18-crown-6), except that the tetrazolato ligands exhibit the isomeric 2,3-eta2-coordination mode and the tetrazolato ligand CN4 cores are bent significantly toward the 18-crown-6 ligands. Molecular orbital calculations were carried out on the model complexes Ba(azolate)2(18-crown-6) (azolate = 1,2-eta2-CHN4, 2,3-eta2-CHN4, and eta2-N5) and demonstrate that the ligand coordination modes are influenced by intramolecular interactions between filled nitrogen orbitals on the azolato ligands and empty C-H sigma* orbitals on the 18-crown-6 ligands.  相似文献   

3.
18-Crown-6 and dicyclohexano-18-crown-6 complexes of potassium 2- and 4-nitrophenoxide, and 18-crown-6 complexes of thallium(I) 2- and 4-nitrophenoxide have been synthesized. Solvent effects on the visible spectra of the nitrophenoxide anions are independent of the nature of the cation and the nature of the complexing agent. The 18-crown-6 complex of thallium(I) 2-nitrophenoxide is a 1:2 complex. All the other complexes are 1:1. X-ray crystallographic examination of the potassium dicyclohexano-18-crown-6 complexes showed the potassium ion is octacoordinated in the 2-nitrophenoxide and heptacoordinated in the 4-nitrophenoxide.  相似文献   

4.
New complex compound, diaqua(18-crown-6)sodium E-2-phenylethenylphosphonate 18-crown-6 E-2-phenylethenylphosphonic acid, [Na(18-crown-6)(H2O)2]+·HO 3 ? PCH=CHPh·18-crown-6·H2O3PCH=CHPh, was obtained and its crystal and molecular structures were studied by the X-ray structural analysis. In this structure the complex cation [Na(18-crown-6)(H2O)2]+ is of guest-host type. The coordination polyhedron of its Na+ cation is a slightly screwed hexagonal bipyramid with the base consisting of all 6 O atoms of 18-crown-6 ligand and with two opposite apexes at two O atoms of two ligand water molecules. In the studied crystal structure the alternating complex cations and 18-crown-6 molecules as well as the molecules of acid and its anion HO 3 ? PCH=CHPh form by means of hydrogen bonds the infinite chains of two different types.  相似文献   

5.
以2-苯氧乙醇为起始剂, 合成了两种新型氮支套索冠醚: N-(2-苯氧乙基)单氮杂-18-冠-6 (18CE)与N-(2-苯氧乙基)单氮杂-15-冠-5 (15CE). 通过红外光谱、核磁共振氢谱和紫外光谱表征了新冠醚及其中间体的结构. 用电导滴定法研究了两冠醚与Na, K, Ag, NH4+, Ni2+, Cu2+, Pb2+和Co2+在25 ℃的配位作用, 计算了1∶1配合物的稳定常数. 实验结果表明, 由于N-(2-苯氧乙基)引入氮杂冠醚环和参与配位, 18CE和15CE配合物的稳定常数分别比单氮杂-18-冠-6, N-(2-羟基乙基)单氮杂-18-冠-6, N-(2-甲氧基乙基)单氮杂-18-冠-6和单氮杂-15-冠-5, N-(2-甲氧乙基)单氮杂-15-冠-5, N-(2-甲氧乙基)单氮杂-15-冠-5的对应配合物明显提高. 配合物的稳定常数和紫外光谱皆提供了支链的苯氧基参与配位的信息.  相似文献   

6.
Crown Ether Complexes of Lead(II). The Crystal Structures of [PbCl(18-Krone-6)][SbCl6], [Pb(18-Krone-6)(CH3CN)3][SbCl6]2 und [Pb(15-Krone-5)2][SbCl6]2 . [PbCl(18-crown-6)][SbCl6] has been prepared in low yield besides [Pb(CH3)2(18-crown-6)][SbCl6]2 by the reaction of Pb(CH3)2Cl2 with antimony pentachloride in acetonitrile solution in the presence of 18-crown-6, forming pale-yellow crystals. The other two title compounds are formed as colourless crystals by the reaction of PbCl2 with antimony pentachloride in acetonitrile solutions in the presence of 18-crown-6 and 15-crown-5, respectively. The complexes were characterized by IR spectroscopy and by crystal structure determinations. [PbCl(18-crown-6)][SbCl6]: Space group P21/c, Z = 8, 5 003 observed unique reflections, R = 0.046. Lattice dimensions at - 80°C: a = 1 386.9; b = 1 642.7; c = 2 172.1 pm, β = 92.95°. The lead atom in the cation [PbCl(18-crown-6)]+ is surrounded in an almost hexagonal-planar construction by the six oxygen atoms of the crown ether and an axially oriented Cl atom. [Pb(18-crown-6)(CH3CN)3][SbCl6]2: Space group P1 , Z = 2, 6 128 observed unique reflections, R = 0.076. Lattice dimensions at - 70°C: a = 1 228.0; b = 1 422.9; c = 1 463.2 pm, α = 69.08°; β = 65.71°; γ = 64.51°. In the cation [Pb(18-crown-6)(CH3CN)3]2+ the lead atom is coordinated by the six oxygen atoms of the crown ether and by the three nitrogen atoms of the acetonitrile molecules. The structure determination is restricted by disorder. [Pb( 15-crown-5)2][SbCI6]2: Space group P63/m, Z = 6, 5 857 observed unique reflections, R = 0.059. Lattice dimensions at -70°C: a = b = 2 198.5; c = 1499.4 pm, α = β = 90°, γ = 120°. In the cation [Pb(l5-crown-5)2]2 the lead atom is sandwich-like coordinated by the ten oxygen atoms of the two crown ether molecules. The structure determination is restricted by disorder.  相似文献   

7.
Ionic Crown Ether Complexes of Tin(II) and Tin(IV): [Sn(15-Crown-5)][SnCl6] and [SnCl3(18-Crown-6)]2[Sn2Cl10]; Syntheses, IR Spectra, and 119Sn-Mössbauer Spectra [Sn(15-crown-5)][SnCl6] ( 1 ,) has been prepared by the reaction of SnCl2, SnCl4, and 15-crown-5 in the molar ratio of 1 : 1 : 1 in acetonitrile solution, forming a white insoluble crystal powder. [SnCl3(18-crown-6)]2[Sn2Cl10] ( 2 ,) as well as [SnCl3(18-crown-6)][BiCl4] · CH3CN ( 3 ,) are prepared by the reaction of SnCl4 with 18-crown-6 (molar ratio 2 : 1), and of SnCl4, 18-crown-6, and BiCl3 (molar ratio 1 : 1 : 1), respectively. According to IR-spectroscopy and 119Sn-Mössbauer-spectroscopy 1–3 , have ionic structures; the cation of 1 , being polymeric via a sandwich-like structure.  相似文献   

8.
Cationic and Anionic Edge-Connected Dimers in [Dy2(dibenzo-18-crown-6)2Cl4][Dy2(CH3CN)2Cl8]. Synthesis and Crystal Structure Colourless single crystals of 2 DyCl3 · dibenzo-18-crown-6 · CH3CN are obtained upon reaction of DyCl3 or KDy2Cl7 with dibenzo-18-crown-6-ether in acetonitrile. The crystal structure (triclinic, P1 , Z = 2; a = 1 105.6(2); b = 1 144.5(3); c = 1 367.8(3); α = 93.46(1); β = 92.27(1); γ = 117.45(1); R = 0.046; Rw = 0.033) contains cationic and anionic edge-connected dimers according to [Dy2(dibenzo-18-crown-6)2Cl4]2+ [Dy2(CH3CN)2Cl8]2+ where Dy1 and Dy2 are coordinated by 3 and 5 chloride ions, respectively.  相似文献   

9.
The nature of the chemical bond in inorganic 6pi aromatic systems such as P4(2-), S4(2+), or S2N2 is a matter of particular interest because the phenomenon of aromaticity is not as well established in these compounds as it is in the classic aromatic hydrocarbons. Here we present the synthesis, NMR spectra, and crystal structures of bis(potassium(18-crown-6))cyclotetraphosphide-ammonia(1/2) (K@18-crown-6)2P4 x 2 NH3, bis(rubidium(18-crown-6))cyclotetraphosphide-cyclotetraarsenide-ammonia(1/3) (Rb@18-crown-6)2(P4)0.85(As4)0.15 x 3 NH3, both containing the 6pi aromatic cyclotetraphosphide anion, P4(2-), and the synthesis and crystal structure of bis(potassium(18-crown-6))cyclotetraarsenide (K@18-crown-6)2As4. As a common motive, all three compounds feature neutral molecules with a tripledecker-like coordination of the cyclotetrapnictide anion between two crown ether-coordinated alkali metal cations. With ab initio calculations on the HF level and by employing the concept of the electron localization function ELF, we established that the cyclotetraarsenide anion, As4(2-), shows electron delocalization primarily through the lone pairs, as does P4(2-), and may consequently also be described as lone pair aromatic.  相似文献   

10.
Deep-blue solutions of Y(2+) formed from Y(NR(2))(3) (R = SiMe(3)) and excess potassium in the presence of 18-crown-6 at -45 °C under vacuum in diethyl ether react with CO at -78 °C to form colorless crystals of the (CO)(1-) radical complex, {[(R(2)N)(3)Y(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 1. The polymeric structure contains trigonal bipyramidal [(R(2)N)(3)Y(μ-CO)(2)](2-) units with axial (CO)(1-) ligands linked by [K(2)(18-crown-6)(2)](2+) dications. Byproducts such as the ynediolate, [(R(2)N)(3)Y](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 2, in which two (CO)(1-) anions are coupled to form (OC≡CO)(2-), and the insertion/rearrangement product, {(R(2)N)(2)Y[OC(═CH(2))Si(Me(2))NSiMe(3)]}[K(18-crown-6)], 3, are common in these reactions that give variable results depending on the specific reaction conditions. The CO reduction in the presence of THF forms a solvated variant of 2, the ynediolate [(R(2)N)(3)Y](2)(μ-OC≡CO)[K(18-crown-6)(THF)(2)](2), 2a. CO(2) reacts analogously with Y(2+) to form the (CO(2))(1-) radical complex, {[(R(2)N)(3)Y(μ-CO(2))(2)][K(2)(18-crown-6)(2)]}(n), 4, that has a structure similar to that of 1. Analogous (CO)(1-) and (OC≡CO)(2-) complexes of lutetium were isolated using Lu(NR(2))(3)/K/18-crown-6: {[(R(2)N)(3)Lu(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 5, [(R(2)N)(3)Lu](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 6, and [(R(2)N)(3)Lu](2)(μ-OC≡CO)[K(18-crown-6)(Et(2)O)(2)](2), 6a.  相似文献   

11.
[La2I2(OH)2(dibenzo-18-crown-6)2]I(I3), a Cationic Dimeric in-cavity Complex with Iodide and Triiodide as Anions Single crystals of [La2I2(OH)2(dibenzo-18-crown-6)2]I(I3) are obtained from the reaction of LaI3 and dibenzo-18-crown-6 in acetonitrile. The crystal structure monoclinic, C2/m, Z = 4, T = 293 [100] K, a = 2179(3) [2162.3(3)], b = 1070.3(3) [1069.6(1)], c = 1118.2(3) [1110.6(1)] pm, β = 93.1(1) [92.83(1)]°, R1 = 0.0601 [0.0411], wR2 = 0.1449 [0.1014] contains hydroxide-bridged cationic dimers and iodide as well as triiodide as anions.  相似文献   

12.
The crystal structure of the title compound, catena-poly[bis[aqua(18-crown-6)­potassium] di­aqua(18-crown-6)­potassium [[tetra-μ-benzoato-2:3κ8O:O′-μ-cyano-1:2κ2C:N-tetra­cyano-1κC-irondirhodium(RhRh)]-μ-cyano-1κC:3′κN] octahydrate], [K(18-crown-6)(H2O)]2[K(18-crown-6)(H2O)2]­[FeRh2(C7H5O2)4(CN)6]·8H2O, where (18-crown-6) is 1,4,7,10,13,16-hexaoxa­cyclo­octa­decane (C12H24O6), has been determined. Ferric cyanides connect the dirhodium units to form a one-dimensional chain compound. [K(18-crown-6-ether)(H2O)2] cations (with inversion symmetry) and [K(18-crown-6-ether)(H2O)] cations (in general positions) are located between the chains.  相似文献   

13.
程维娜  胡新根  邵爽 《物理化学学报》2013,29(10):2114-2122
利用等温滴定微量热法测定了298.15 K时12-冠-4、15-冠-5、18-冠-6和4,13-二氮杂-18-冠-6四种冠醚在纯水及不同质量分数(w=0-0.3)的N,N-二甲基甲酰胺(DMF)+H2O混合物中的稀释焓, 根据McMillan-Mayer理论计算得到相应的焓对作用系数(hxx). 实验发现, hxx均为较大的正值, 表明在冠醚-冠醚自相互作用中疏水性成分占绝对优势, 主要表现为两种机制: (1) 当疏水-疏水作用发生时, 共球交盖使得水结构形成减少, 对hxx有正的贡献; (2) 当疏水-亲水作用发生时, 共球交盖使得水结构破坏增加, 对hxx有正的贡献. 此外, 四种冠醚hxx的大小关系为: hxx(18-冠-6)>hxx(4,13-二氮杂-18-冠-6)≈hxx(15-冠-5)>hxx(12-冠-4), 表明冠醚环越大, 疏水-疏水作用越强, 存在显著的大环疏水效应.  相似文献   

14.
The dibenzo-18-crown-6 derivatives such as di(nitrobenzo)-18-crown-6 and di(aminobenzo)-18-crown-6 were synthesized by nitration reaction and catalytic hydrogenation with high selectivity. The chemical structures were determined by FTIR, 1H NMR, 13C NMR, and UV. Regarding the mixture of Ac2O and HNO3 as nitrating agent, the reaction exhibited commendable trans-isomer selectivity. Effects of nitrating agent ratio, reaction temperature and reaction time on yield of trans-di(nitrobenzo)-18-crown-6 were investigated. The yield of trans-di(nitrobenzo)-18-crown-6 was 62.9% for nitrating agent ratio of 1/1, reaction temperature of 50?°C and reaction time of 5?h. Moreover, effect of reaction time on trans-di(aminobenzo)-18-crown-6 was also studied.  相似文献   

15.
A new procedure for the oxidative cleavage of alken-3-ols to α-alkoxy aldehydes has been developed using a combination of OsO4/Et3N/KIO4/di-benzo-18-crown-6-ether in benzene/water. This extremely mild method has been applied to several 2-alkoxy-2-(3,4,5-trimethoxyphenyl)acetaldehydes.  相似文献   

16.
Crystal Structures of the Polytellurides [Ca(DMF)6]Te4, [Sr(15-Crown-5)2]Te4 · H2O, {[BaCl(18-Crown-6)(DMF)2]2[BaCl(18-Crown-6)(DMF) (H2O)]2(Te4)2}, and [Ph3PNPPh3]2Te5 · 2 DMF The title compounds were formed by alkalimetal polytelluride solutions in dimethylformamide (DMF) in the presence of the corresponding counter ions as well as in the presence of 15-crown-5 or 18-crown-6. Single crystals were obtained upon using additional diethylether. [Ca(DMF)6]Te4: Space group C2/c, Z = 4, 1024 observed unique reflections, R = 0.055. Lattice dimensions at ?70°C: a = 1776.1; b = 813.0 c = 2545.9pm; β = 102.90°. The compound consists of centrosymmetric [Ca(DMF)6]2+ ions, in which the calcium ions are octahedrally coordinated by the six oxygen atoms of the DMF molecules, and chain-like Te [Sr)15-crown-5)2]Te4 · H2O: Space group C2/c, Z = 4, 3322 observed unique reflections, R = 0.058. Lattice dimensions at ?70°C: a = 1450.5; b = 1407.3; c = 1660.9 pm; β = 110.22°. The compounds forms centrosymmetric cations [Sr(15-crown-5) 2]2+, in which the Sr2+ ion is sandwich-like surrounded by the ten oxygen atoms of the crown ether molecules, and chain-like Te42? ions, which are associated in the lattice forming polymeric chains. {[BaCl(18-crown-6)(DMF) 2]2[BaCl(18-crown-6)(DMF)· (H2O)] 2(Te4)2}: Space group P1 , Z = 1, 3189 observed unique reflections, R = 0.054. Lattice dimensions at 19°C: a = 986.1; b = 1052.8; c = 2696.4 pm; α = 89.34°; β = 88.68°; γ = 89.56°. The compound consists of chain-like Te ions without symmetry and of the two somewhat different cations [BaCl(18-crown-6)(DMF) 2]22+, in which the Ba2+ ions dimerize via centroysmmetric rings. Along with the six oxygen atoms of the crown ether molecules and the oxygen atoms of the DMF molecules, the oxygen atoms of the DMF and water molecule, respectively, the Ba+ ions achieve coordination number ten. [Ph3PNPPh3]2Te5 · 2DMF: Space group Pc, Z = 2, 5971 observed unique reflections, R = 0.058. Lattice dimensions at 20°C: a = 20°C: a = 1085.2; b = 1287.0; c = 2715.9 pm; β = 90.19°. The compounds consists of [Ph3PNPPh3]+ ions, chain-like Te52? ions, and incorporate DME molecules without bonding interaction. The 52? ions are associate via polymeric chains in which left- and right handed individuals are alternating.  相似文献   

17.
A novel sterically demanding bis(4-benzhydryl-benzoxazol-2-yl)methane ligand 6 (4−BzhH2BoxCH2) was gained in a straightforward six-step synthesis. Starting from this ligand monomeric [M(4-BzhH2BoxCH)] (M=Na ( 7 ), K ( 81 )) and dimeric [{M(4-BzhH2BoxCH)}2] (M=K ( 82 ), Rb ( 9 ), Cs ( 10 )) alkali metal complexes were synthesised by deprotonation. Abstraction of the potassium ion of 8 by reaction with 18-crown-6 resulted in the solvent separated ion pair [{(THF)2K@(18-crown-6)}{bis(4-benzhydryl-benzoxazol-2-yl)methanide}] ( 11 ), including the energetically favoured monoanionic (E,E)-(4-BzhH2BoxCH) ligand. Further reaction of 4−BzhH2BoxCH2 with three equivalents KH and two equivalents 18-crown-6 yielded polymeric [{(THF)2K@(18-crown-6)}{K@(18-crown-6)K(4-BzhBoxCH)}]n (n→∞) ( 12 ) containing a trianionic ligand. The neutral ligand and herein reported alkali complexes were characterised by single X-ray analyses identifying the latter as a promising precursor for low-valent main group complexes.  相似文献   

18.
Extracton, of Am3+ in benzene with 2-thenoyltrifluoroacetone (HTTA) and crown ethers (CEs) such as 15-crown-5, 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, dicyclohexano-24-crown-8, and dibenzo-24-crown-8 was investigated. Synergistic effect by CE was observed regardless of the kind of CE examined. The extracted species was found to be Am(TTA)3(CE), and adduct formation constants between Am(TTA)3 and CE in the organic phase were determined. The sequence of constant could not be explained only by basicity of CE and the steric effect of CE should be taken into account to elucidate the adduct complex formation.  相似文献   

19.
Two new dithia-crowns containing a hydroxy group and 1,4,7,10-tetrathia-18-crown-6 containing an allyl-oxymethyl substituent were prepared in good yields. Two of these crowns were covalently attached to silica gel. The silica gel-bound thia-crowns were used to separate gold( III ), palladium( II ), silver( I ) and mercury( II ) ions from an aqueous 0.1 M nitric acid solution which also contained 1.0 M ferric chloride.  相似文献   

20.
A new complex compound, [K2(18-crown-6)2[K(18-crown-6)(EtOH)]2[Er(NCS)6](SCN) (I), was synthesized and its crystal structure was studied by X-ray diffraction. In this work, the synthes and X-ray difraction stady of the crystals of a new complex, hexakis (isothiocyanato) erbiu(III) thiocyanate bis(18-crown-6) dipotassium bis(18-crown-6) ethanolpotassium], [K2(18-crown-6)2][K(18-crown-6)(ETON)]2[Er(NCS)6(SCN)(I)] are described. In crystal I, the alternating [Er(NCS)6]3? anions and binuclear complex cation [K(18-crown-6)2]2+ from infinite chains via the F-S bonds, while two complex cations [K(18-crown-6)(ETON)]+ and the statistically disordered SCN? anion between them are linked by the hydragen bonds O-H…S and O-H…N. Complex I contains the host-guest complex cations [K2(18-crown-6)2)]2+ and [K(18-crown-6)(ETON)]+ [1]. The alternating octabedral [Er(NCS)6]3? anions and binuclear complex cations [K2(18-crown-6)2]2+of crystal I form infinite chains via the K-S bonds, while two complex cations [K(18-crown-6)(EtOH)]+ and the statistically disordered SCN? anion lying between them are linked by interionic hydrogen bonds O-H…S and O-H…N. Complex I contains the host-guest complex cations [K2(18-crown-6)2]2+ and [K(18-crown-6)(EtOH)]+ [1].  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号