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1.
To determine whether centrally released vasopressin influences thirst, observations of osmotic thirst threshold, osmotic load excretion and postloading restitution of plasma osmolality were made in dogs in control experiments and during infusion of AVP antagonists into the third ventricle. Significant elevation of osmotic thirst threshold was elicited by infusion of d(CH 2) 5AVP at a rate of 0.2–2.0 μg·min −1 and of d(Et 2)AVP at a rate of 0.3 μg·min −1 (V 1 antagonists, weak V 2 agonists) as well as by administration of d(CH 2) 5[D-Ile 2,Abu 4]AVP at a rate of 0.4 μg·min −1 (potent V 2 antagonist, weak V 1 antagonist). Administration of d(CH 2) 5AVP at a rate of 2.0 μg·min −1 was associated with a significant suppression of the postloading water intake and osmotic load excretion and with a delay in restitution of plasma osmolality. These findings indicate that centrally released vasopressin may participate in the control of thirst. 相似文献
2.
Autoradiographic analysis of 1, 8, 16 and 26-day-old rat brains showed 3H-arginine 8-vasopressin ( 3H-AVP) binding to the cingulate gyrus-dorsal hippocampus (CG) only in the 8-day-old rat brain. Saturation analysis of CG membranes prepared from pups (7–10 days) and adults (90 days) revealed a small but significant increase in binding site concentration in adults compared to pups. However, the K d of the 3H-AVP binding site increased significantly with age. The K d of 3H-AVP binding to pup CG membranes was 0.9±0.1 nM, while the adult CG was 5.7±1.0 nM. The pharmacological specificity of 3H-AVP binding sites in the pup and adult CG was similar, but differed markedly from the profile observed in adult septal membranes. The primary specificity difference between the pup CG and septum was the reduced potency of certain V 1 receptor antagonists. In competition experiments the CG binding site showed a reduced affinity for the V 1 antagonist, [d(CH 2) 5, Tyr(Me)]AVP. This reduced affinity for the V 1 antagonist was also documented autoradiographically using 3H-[d(CH 2) 5, Tyr(Me)]AVP. The data suggest that the 3H-AVP binding site expressed in the pup CG is not identical to the V 1 type receptor present in the periphery and brain of the adult rat. 相似文献
3.
Rapid reactions occur between [Os VI(tpy)(Cl) 2(N)]X (X = PF 6−, Cl −, tpy = 2,2′:6′,2″-terpyridine) and aryl or alkyl phosphi nes (PPh 3, PPh 2Me, PPhMe 2, PMe 3 and PEt 3) in CH 2Cl 2 or CH 3CN to give [Os IV(tpy)(Cl) 2(NPPh 3)] + and its analogs. The reaction between trans-[Os VI(tpy)(Cl) 2(N)] + and PPh 3 in CH 3CN occurs with a 1:1 stoichiometry and a rate law first order in both PPh 3 and Os VI with k(CH 3CN, 25°C) = 1.36 ± 0.08 × 10 4 M − s −1. The products are best formulated as paramagnetic d 4 phosphoraniminato complexes of Os IV based on a room temperature magnetic moment of 1.8 μ B for trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6), contact shifted 1H NMR spectra and UV-Vis and near-IR spectra. In the crystal structures of trans-[Os IV(tpy)(Cl) 2( NPPh 3)](PF 6)·CH 3CN (monoclinic, P2 1/ n with a = 13.384(5) Å, b = 15.222(7) Å, c = 17.717(6) Å, β = 103.10(3)°, V = 3516(2) Å 3, Z = 4, Rw = 3.40, Rw = 3.50) and cis-[Os IV(tpy)(Cl) 2(NPPh 2Me)]-(PF 6)·CH 3CN (monoclinic, P2 1/ c, with a = 10.6348(2) Å, b = 15.146(9) ÅA, c = 20.876(6) Å, β = 97.47(1)°, V = 3334(2) Å 3, Z = 4, R = 4.00, Rw = 4.90), the long Os-N(P) bond lengths (2.093(5) and 2.061(6) Å), acute Os-N-P angles (132.4(3) and 132.2(4)°), and absence of a significant structural trans effect rule out significant Os-N multiple bonding. From cyclic voltammetric measurements, chemically reversible Os V/IV and Os IV/III couples occur for trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6) in CH 3CN at +0.92 V (Os V/IV) and −0.27 V (Os IV/III) versus SSCE. Chemical or electrochemical reduction of trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6) gives isolable trans-Os III(tpy)(Cl) 2(NPPh 3). One-electron oxidation to Os V followed by intermolecular disproportionation and PPh 3 group transfer gives [Os VI(tpy)Cl 2(N)] +, [OS III(tpy)(Cl) 2(CH 3CN)] + and [Ph 3=N=PPh 3] + (PPN +). trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6) undergoes reaction with a second phosphine under reflux to give PPN + derivatives and Os II(tpy)(Cl) 2(CH 3CN) in CH 3CN or Os II(tpy)(Cl) 2(PR 3) in CH 2Cl 2. This demonstrates that the Os VI nitrido complex can undergo a net four-electron change by a combination of atom and group transfers. 相似文献
4.
The solution of [RhCl(PPh 3) 3] in acidic 1-ethyl-3-methylimidazolium chloroaluminate(III) ionic liquid (AlCl 3 molar fraction, xAlCl3=0.67) was investigated by 1H and 31P{ 1H} NMR. One triphenyl phosphine is lost from the complex and is protonated in the acidic media, and cis-[Rh(PPh 3) 2ClX], (2), where X is probably [AlCl 4] −, is formed. On, standing, 2 is converted to trans-[Rh(H)(PPh 3) 2X], (3). The reaction of 2 and H 2 also produces trans-[Rh(H)(PPh 3) 2X], (3). 1H and 31P{ 1H} NMR support the suggestion that a weak ligand such as [AlCl 4] −, present in solution may interact with the metal centre. When [RhCl(PPh 3) 3] is dissolved in CH 2Cl 2/AlCl 3/HCl for comparison, two exchanging isomers of what is probably [RhH{(μ-Cl) 2AlCl 2}{(μ-Cl)AlCl 3}(PPh 3) 2], (6) and (7), are formed. 相似文献
5.
[Fe(TIM)(CH 3CN) 2](PF 6) 2 (1) (TIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclodeca-1,3,8,10-tetraene) forms a complex with NO reversibly in CH 3CN (53±1% converted to the NO complex) or 60% CH 3OH/40% CH 3CN (81±1% conversion). Quantitative NO complexation occurs in H 2O or CH 3OH solvents. The EPR spectrum of [Fe(TIM)(solvent)NO] 2+ in frozen 60/40 CH 3OH/CH 3CN at 77 K shows a three line feature at g=2.01, 1.99 and 1.97 of an S=1/2FeNO 7 ground state. The middle line exhibits a three-line N-shf coupling of 24 G indicating a six-coordinate complex with either CH 3OH or CH 3CN as a ligand trans to NO. In H 2O [Fe(TIM)(H 2O) 2] 2+ undergoes a slow decomposition, liberating 2,3-butanedione, as detected by 1H NMR in D 2O, unless a π-acceptor axial ligand, L=CO, CH 3CN or NO is present. An equilibrium of 1 in water containing CH 3CN forms [Fe(TIM)(CH 3CN)(H 2O)] 2+ which has a formation constant KCH3CN=320 M −1. In water KNOKCH3CN since NO completely displaces CH 3CN. [Fe(TIM)(CH 3CN) 2] 2+ binds either CO or NO in CH 3CN with KNO/ KCO=0.46, sigificantly lower than the ratio for [Fe II(hemes)] of 1100 in various media. A steric influence due to bumping of β-CH 2 protons of the TIM macrocycle with a bent S=1/2 nitrosyl as opposed to much lessened steric factors for the linear Fe---CO unit is proposed to explain the lower KNO/ KCO ratio for the [Fe(TIM)(CH 3CN)] 2+ adducts of NO or CO. Estimates for formation constants with [Fe(TIM)] 2+ in CH 3CN of KNO=80.1 M −1 and KCO=173 M − are much lower than to hemoglobin (where KNO=2.5×10 10 M −1 and KCO=2.3×10 7) due to a reversal of steric factors and stronger π-backdonation from [Fe II(heme)] than from [Fe II(TIM)(CH 3CN)] 2+. 相似文献
6.
The trinuclear complexes [Ag(PR 3) 2] 2[Ni(mnt) 2] and [AgL] 2[Ni(mnt) 2] have been prepared by reactions of (NEt 4) 2[Ni(mnt) 2] and Ag 2SO 4 with alkyl phosphines (PR 3=P(CH 3) 3 (PMe 3) for 1, P(C 2H 5) 3 (PEt 3) for 2 and P(C 6H 11) 3 (PCy 3) for 3), or with chelating diphosphines (L=1,1′-bis(diphenylphosphino)ferrocene (dppf) for 4 and bis(diphenylphosphino)methane (dppm) for 5). The structures of all the complexes have been determined by X-ray crystallography. Interactions between the [Ag(PR 3) 2] + and [Ni(mnt) 2] 2− groups occur in compounds 1 and 2 with Ni---Ag distances of 3.063(4) and 2.9311(6) Å, respectively. Only one sulfur atom of each mnt ligand bridged [Ag(PR 3) 2] + cations and [Ni(mnt) 2] 2− anions in compound 1 through 3 with Ag---S distances of about 2.7 Å. There is no interaction between Ag and Ni in compound 3 due to the flexibility of the cyclohexyl groups. Interactions between [AgL] + and [Ni(mnt) 2] 2− groups also occur in compound 4 with a much shorter Ag---Ni distance of 2.7213(7) Å, while silver atoms and the NiS 4 plane in compound 4 make a chair conformation with Ag---S distances of about 2.8 Å. In compound 5, dppm bridges two silver atoms, and interaction between silver atoms occurs at a distance of 2.9859(11) Å, and only one sulfur atom of mnt is used to bridge Ni and Ag atoms with Ag---S distances of 2.582(3) and 2.663(3) Å. 相似文献
7.
The reversible equilibrium conversion under H 2 of [RuCl(dppb) (μ-Cl)] 2 (1) to generate (η 2-H 2) (dppb) (μ-Cl) 3RuCl(dppb) in CH 2Cl 2 (dppb = Ph2P( CH2) 4PPh2) has been studied at 0–25 °C by UV-Vis and 31P{ 1H} NMR spectroscopy, and by stoppe kinetics; the equilibrium constant and corresponding thermodynamic parameters, and the forward and reverse rate constants at 25 °C have been determined. A measured Δ H° value of 0 kJ mol −1 allows for an estimation of an exothermicity of 60 kJ mol −1 for binding an η 2-H 2 at an Ru(II) centre; a Δ S° value of 60 J mol −1 K −1 indicates that in solution 1 contain s coordinated CH 2Cl 2. The kinetic and thermodynamic data are compared to those obtained from a previously studied hydrogenation of styrene catalyzed by 1. Preliminary findings on related systems containing Ph 2P(CH 2) 3PPh 2 and (C 6H 11) 2P(C 6H 11) 2 are also noted. 相似文献
8.
A series of borane and monoiodoborane derivatives of bis(diphenylphosphino)alkanes. (C 6H 5) 2P--- (CH 2) n---P(C 6H 5) 2 in which n has values of 2 through 4 has been synthesized. Only compounds with the formulae [(C 6H 5) 2P] 2(CH 2) n · (BH 3) 2 and (C 6H 5) 2P] 2CH 2) n · BH 2I were isolable, the latter being boronium iodides. The compounds were characterized by their melting points, elemental analyses, molar conductivities, infrared spectroscopy, and 1H and 11B nuclear magnetic resonance spectroscopy. The relationship between the length of the carbon chain and the 11B NMR chemical shift is discussed. 相似文献
9.
Reactions of [(PPh 3) 2Pt(η 3-CH 2CCPh)]OTf with each of PMe 3, CO and Br − result in the addition of these species to the metal and a change in hapticity of the η 3-CH 2CCPh to η 1-CH 2CCPh or η 1-C(Ph)=C=CH 2. Thus, PMe 3 affords [(PMe 3) 3Pt(η 1-C(Ph)=C=CH 2)] +, CO gives both [ trans-(PPh 3) 2Pt(CO)(η 1-CH 2CCPh)] + and [ trans-(PPh 3) 2Pt(CO)(η 1-C(Ph)=C=CH 2)] +, and LiBr yields cis-(PPh 3) 2PtBr(η 1-CH 2CCPh), which undergoes isomerization to trans-(PPh 3) 2PtBr(η 1-CH 2CCPh). Substitution reactions of cis- and trans-(PPh 3) 2PtBr(η 1-CH 2CCPh) each lead to tautomerization of η 1-CH 2CCPh to η 1-C(Ph)=C=CH 2, with trans-(PPh 3) 2PtBr(η 1-CH 2CCPh) affording [(PMe 3) 3Pt(η 1-C(Ph)=C=CH 2)] + at ambient temperature and the slower reacting cis isomer giving [ trans-(PPh 3)(PMe 3) 2Pt(η 1-C(Ph)=C=CH 2)] + at 54 °C . All new complexes were characterized by a combination of elemental analysis, FAB mas spectrometry and IR and NMR ( 1H, 13C{ 1H} and 31P{ 1H}) spectroscopy. The structure of [(PMe 3) 3Pt(η 1-C(Ph)=C=CH 2)]BPh 4·0.5MeOH was determined by single-crystal X-ray diffraction analysis. 相似文献
10.
The synthesis of the tetradentate pendant arm macrocycles 1,4,7-triazacyclononane- N-acetate (L 1) and N-(2-hydroxybenzyl)-1,4,7-triazacyclononane (HL 2) and their coordination chemistry with vanadium(IV) and (V) are reported. The following mononuclear species have been prepared and characterized by UV-Vis, IR spectroscopy: [L 1V IVO(NCS)] (1), [L 1VO 2]·H 2O (2), [L 2VO(NCS)] (3), [L 2VO(NCS)]Cl (4), and [L 2VO 2] (5). In addition, the dinuclear, mixed valent complexes [L 21V 2O 3]Br (6), [L 22V 2O 3](ClO 4)·0.5acetone (7), and the homovalent complex [L 22V 2O 3](ClO 4) 2 (8) have been synthesized. Complexes 2, 3, 6 and 7 have been characterized by single crystal X-ray crystallography. Crystal data: 2, space group P2 1c, a=9.944(4), b=6.701(3), c=18.207(8)Å, β=102.88(3)°, V=1182.7 Å 3, Z=4, Dcalc=1.51 g cm −3, R=0.049 based on 4760 reflections; 3, space group Pbca, A=11.003(6), b=14.295(7), C=20.21(1) Å, V=3178.8 Å 3, Z=8, Dcalc=1,50 g cm −3, R=0.057 based on 1049 reflections; 6, space Pbcn, a=12.922(3), B=13.852(3), C=12.739(3) Å, V=2280.3 Å 3, Z=4, Dcalc=1,75 g cm −3, R=0.047 based on 1172 reflections; 7, space group C2/ c, A=23.553(9), B=13.497(5), C=20.951(8) Å, β=90.03(3)°, V=6660.2 Å 3, Z=8, Dcalc=1.49 g cm −3, R=0.053 based on 3698 reflections. Complexes 6 and 7 are mixed valent V(IV)/(V) complexes containing the [OV---O---VO] 3+ core. In the solid state 6 belongs to class III (delocalized) and 7 to class I (localized) according to the Robin and Day classification of mixed valent compounds. A rationale for these differing electronic structures is given. 相似文献
11.
The trinuclear clusters [Pd 3(μ-dppm) 3(CO)] 2+ and [PtPdCo(μ-dppm) 2(CO) 3(CN tBu)] + exhibit a large and a small cavity, respectively, formed by the phenyl rings of the bridging diphosphine ligands. Their binding constants ( K11) with halide ions (X −) were obtained by UV-Vis spectroscopy. The binding ability varies as I − > Br − > Cl −, and [Pd 3(μ-dppm) 3(CO)] 2+ > [ptPdCo(μ-dppm) 2-(CO) 3(CN tBu)] +. The MO diagram for the related cluster [Pd 2Co(μ-dppm) 2(CO) 4] + has been addressed theoretically in order to predict the nature of the lowest energy electronic bands. For this class of compounds, the lowest energy bands are assigned to charge transfers from the Co center to the Pd 2 centers. 相似文献
12.
Binding of the labeled anticonvulsant drug [ 3H]dibenzocycloalkenimine ( 3H]MK-801) to the N-methyl-D-aspartate (NMDA) receptor and its dissociation from the receptor at 25°C are slow processes, both of which follow first order kinetics ( t1/270 and 180 min, respectively). Both reactions are markedly accelerated by glutamate and glycine ( t1/22-8 and 4 min, respectively), which allow bimolecular association kinetics of the labeled drug with the receptors whereas equilibrium binding of [ 3H]MK-801 ( Kd 2–4 nM) is hardly affected by glutamate and glycine. The data suggest that MK-801 acts as a steric blocker of the NMDA receptor channel. The competitive antagonist D-(−)-2-amino-5-phosphovaleric acid (AP-5) freezes the receptor in a state which precludes either binding of [ 3H]MK-801 to the receptor channel or its dissociation from it. These findings have therapeutic implications. 相似文献
13.
Cockerels with permanent cannulas in the brachial artery and vein were put into isolated slings. Arterial pressure and heart rate were continuously recorded. Following habituation, tests were initiated. In each cockerel 2 nmol/kg of the tested neurohypophysial peptide (NPs) or analogue was IV injected six times at 6-min intervals. Arginine vasotocin (AVT) caused an immediate vasodepressor (VDP) effect and tachycardia. These subsided within 20–30 s and were followed by a vasopressor (VP) response and bradycardia. On repeated injections of AVT, the VDP response declined and bradycardia intensified. Arginine vasopressin (AVP), oxytocin (OT), and mesotocin (MT) had short-lasting VDP effect in the following order of potency: OT = MT > AVT > AVP. Only AVT and, more effectively, AVP, caused a VP response. The VDP effect of MT and OT declined on repeated injections. When AVT was injected after three injections of MT, it had mostly an immediate VP effect. Although the V 1 agonist is VP in chickens, at the dose used the V 1 antagonist, [d(CH 2) 5,O-Me-Tyr 2]AVP, had no effect on cardiovascular responses to AVT. Pretreatment with OT antagonist, [d(CH 2) 5-O-Me-Tyr 2,Thr 4,Tyr 9,Orn 8]VT, abolished the VDP effect of all NPs. Thus, MT had no effect on blood pressure, whereas AVP and, more effectively, AVT, had a marked immediate VP action. In chickens the VDP effect of NPs is probably mediated by an OT/MT-like receptor, wherein the peptide's ring structure, shared by AVT, OT, and MT, is important. The VP effect is mediated by a receptor only partially similar to the mammalian V 1 receptor, where arginine in position 8, shared only by AVT and AVP, is necessary for action, and the native AVT is more effective than the mammalian AVP. This receptor reacts to the V 1 agonist but probably not to the V 1 antagonist. 相似文献
14.
Carbonylation of the anionic iridium(III) methyl complex, [MeIr(CO) 2I 3] − (1) is an important step in the new iridium-based process for acetic acid manufacture. A model study of the migratory insertion reactions of 1 with P-donor ligands is reported. Complex 1 reacts with phosphites to give neutral acetyl complexes, [Ir(COMe)(CO)I 2L 2] (L = P(OPh) 3 (2), P(OMe) 3 (3)). Complex 2 has been isolated and fully characterised from the reaction of Ph 4As[MeIr(CO) 2I 3] with AgBF 4 and P(OPh) 3; comparison of spectroscopic properties suggests an analogous formulation for 3. IR and 31P NMR spectroscopy indicate initial formation of unstable isomers of 2 which isomerise to the thermodynamic product with trans phosphite ligands. Kinetic measurements for the reactions of 1 with phosphites in CH 2Cl 2 show first order dependence on [1], only when the reactions are carried out in the presence of excess iodide. The rates exhibit a saturation dependence on [L] and are inhibited by iodide. The reactions are accelerated by addition of alcohols (e.g. 18× enhancement for L = P (OMe) 3 in 1:3 MeOH-CH 2Cl 2). A reaction mechanism is proposed which involves substitution of an iodide ligand by phosphite, prior to migratory CO insertion. The observed rate constants fit well to a rate law derived from this mechanism. Analysis of the kinetic data shows that k1, the rate constant for iodide dissociation, is independent of L, but is increased by a factor of 18 on adding 25% MeOH to CH 2Cl 2. Activation parameters for the k1 step are Δ H≠ = 71 (±3) kJ mol −, Δ S≠ = −81 (±9) J mol −1 K −1 in CH 2Cl 2 and Δ H≠ = 60(±4) kJ mol −1, Δ S≠ = −93(± 12) J mol −1 K −1 in 1:3 MeOH-CH 2Cl 2. Solvent assistance of the iodide dissociation step gives the observed rate enhancement in protic solvents. The mechanism is similar to that proposed for the carbonylation of 1. 相似文献
15.
The hydrothermal reactions of (Ph 4P)[VO 2Cl 2] and H 2C 2O 4 at 150 and 125°C yield (Ph 4P) 2[V 2O 2(H 2O) 2(C 2O 4) 3]·4H 2O (1) and (Ph 4P)[VOCl(C 2O 4)] (2), respectively. The structure of the molecular anion of 1 consists of a binuclear unit of oxovanadium(IV) octahedra bridged by a bisbidentate oxalate group. The VO 6 coordination geometry at each vanadium site is defined by a terminal oxo group, an aquo ligand, and four oxygen donors — two from the bisbidentate bridging oxalate and two from the terminal bidentate oxalate. The structure of 2 consists of discrete Ph 4P + cations occupying regions between [VOCl(C 2O 4)] −∞ spiral chains. The structure of the one-dimensional anionic chain exhibits V(IV) octahedra bridged by bisbidentate oxalate groups. Crystal data: 1·4H 2O, monoclinic P2 1/ n, A = 12.694(3), B = 12.531(3), C = 17.17(3) Å, β = 106.32(2)°, V = 2621.3(13) Å 3, Z = 2, Dcalc = 1.501 g cm −3, structure solution and refinement converged at a conventional residual of 0.0518; 2, tetragonal P4 3, A = 12.145(2), C = 15.991(3) Å, V = 2358.7(12) Å 3, Z = 4, R = 0.0452. 相似文献
16.
Affinity probes for the noncompetitive blocker or picrotoxinin site of the γ-aminobutyric acid (GABA)-gated chloride channel were designed for four types of applications: photoaffinity reagents to covalently label the binding site; fluorescent probes for receptor analysis; biotinylated compounds and agarose/sepharose conjugates for affinity chromatography; ligand-protein/enzyme conjugates for immunoassay. These 5 e- tert-butyl-2 e-[4-(substituted-ethynyl)phenyl]-1,3-dithianes were optimized by structure-activity studies for potency as inhibitors of 3H ethynylbicycloorthobenzoate binding to bovine brain membranes, measured as the concentration for 50% inhibition (IC 50). Preferred compounds are 5 e-(CH 3) 3CCH(CH 2S) 2CH-2 e-C 6H 4-4-CCCH 2OCH 2C(O)R, wherein R confers the following properties and 1C 50 values: R = SCH 2CH 2SCH 2C(O)C 6H 4-4-N 3, photo-affinity, 9 nM; R = NHCH 2CH 2NHC(O)C 6H 2-2-OH,5-1,4-N 3, photoaffinity, 105 nM; R = SCH 2CH 2S-4-benzofurazan-7-NO 2, fluorescent, 13 nM; R = SCH 2CH 2SCH 2-5-fluorescein, fluorescent, 27 nM; R = NHCH 2CH 2NH[C(O)(CH 2) 5NH] 2-biotin, affinity chromatography, 190 nM. The most potent photoaffinity ligand (IC 50 9 nM) was labeled at 7 Ci mmol −1 by reacting the appropriate thiol with 3H 4-azidophenacyl bromide (obtained by alumina-catalyzed tritium exchange of its enolizable hydrogens). The first steps have been taken in using the NCB site for affinity chromatography of the GABA A receptor in CHAPS-solubilized bovine brain membranes with the dithiane-biotin probe and an avidin-acrylic bead system or with an analogous dithiane-agarose/sepharose column eluting with GABA or dithiane as above (R = OH). A protein conjugate of a related dithiane-monosulfone elicited production of specific antisera in rabbits. These findings illustrate the diversity and utility of new affinity probes prepared in the alkynylphenyldithiane series. 相似文献
17.
The formation of three [Tl(en) n] 3+ complexes ( n=1–3) in a pyridine solvent has been established by means of 205Tl and 1H NMR. Their stepwise stability constants based on concentrations, Kn=[Tl(en) n 3+]/{[Tl(en) n−1 3+]·[en]}, at 298 K in 0.5 M NaClO 4 ionic medium in pyridine, were calculated from 205Tl NMR integrals: log K1=7.6±0.7; log K2=5.2±0.5 and log K3=2.64±0.05. Linear correlation between both the 205Tl NMR shifts and spin–spin coupling 205Tl– 1H versus the stability constants has been found and discussed. A single crystal with the composition [Tl(en) 3](ClO 4) 3 was synthesized and its structure determined by X-ray diffraction. The Tl 3+ ion is coordinated by three ethylenediamine ligands via six N-donor atoms in a distorted octahedral fashion. 相似文献
18.
The reactions of the polysulfur and selenium cationic clusters S 82+ and Se 82+ with various iron carbonyls were investigated. Several new chalcogen containing iron carbonyl cluster cations were isolated, depending on the nature of the counteranion. In the presence of SbF 6− as a counterion, the cluster [Fe 3(E 2) 2(CO) 10] [SbF 6] 2·SO 2 (E = S, Se) could be isolated from the reaction of E 82+ and excess iron carbonyl. The cluster is a picnic-basket shaped molecule of two iron centers linked by two Se 2 groups, with the whole fragment capped by an Fe(CO) 4 group. Crystallographic data for C 10O 12Fe 3Se 4Sb 2F 12S (I): space group monoclinic P2 1/ c, A = 11.810(9), b = 24.023(6), c = 10.853(7) Å, β = 107.15(5)°, V = 2942(3) Å 3, Z = 4, R = 0.0426, Rw = 0.0503. When Sb 2F 11− is present as the counterion, or Se 4[Sb 2F 11] 2 is used as the cluster cation source, a different cluster can be isolated, which has the formula [Fe 4(Se 2) 3(CO) 12] [SbF 6] 2·3SO 2. The dication contains two Fe 2Se 2 fragments bridged by an Se 2 group. Crystallographic data for C 12O 18Fe 4Se 6Sb 2F 12S 3 (III): space group triclinic
, b = 18.400(9), C = 10.253(4) Å, = 93.10(4), β = 103.74(3), γ = 93.98(3)°, V = 1995(1) Å 3, Z = 2, R = 0.0328, Rw = 0.0325. The CO stretches in the IR spectrum all show a large shift to higher wavenumbers, suggesting almost no τ backbonding from the metals. This also correlates with the observed bond distances. All the compounds are extremely sensitive to air and water, and readily lose SO 2 when removed from the solvent. Thus all the crystals were handled at −100°C. The clusters seem to be either insoluble or unstable in all solvents investigated. 相似文献
19.
The kinetics and equilibria of complex formation by Ga(III) with NCS − in aqueous solution have been measured over a range of acidities and temperatures, the contributing paths to the reaction resolved, and their rate constants and activation parameters determined. The hydrolysis equilibria required to carry out this resolution of kinetic behaviour have also been measured. Unlike the other reported complexation reactions of Ga(III) in aqueous solution, the separate reaction pathways can be assigned with no ambiguity. At 25 °C and ionic strength 0.5 M, the observed forward rate constant for the complex formation is described by {k1 + k2K1h/[H+] + k3K1hK2h/[H+]2} M−1 s−1. For these conditions, the first and second successive hydrolysis constants of Ga(H2O)63+ are given by pK1h = 3.69 ± 0.01 and pK2h = 3.74 ± 0.04. The rate constants corresponding to the reactions of the species Ga(H2O)63+, Ga(H2O)5(OH)2+ and Ga(H2O)4(OH)2+ with NCS− are k1 = 57 ± 4 M−1 −1, k2 = (1.08 ± 0.01) × 105 M−1 s−1 and k3 = 3 × 106 M−1 s−1 respectively. The complexation equilibrium quotient [GaNCS2+]/([Ga3+][NCS−]) has been independently determined by spectrophotometric titration to be 20.8 ± 0.3 M−1 at 25 °C and ionic strength 0.5 M. These kinetic results lead to an interpretation of the data, and a reinterpretation of other data for aquo-Ga(III) complex formation kinetics from the literature which support the assignment of a dissociative interchange mechanism for these reactions rather than the associative activation mode sometimes proposed. 相似文献
20.
Four complexes of the type [Cu 4I 4(CH 3CN) 2(L) 2], L = aniline derivative: Cu 4I 4(CH 3CN) 2(2,6-dimethylaniline) 2 (I), triclinic,
, a = 12.449(3), B = 14.108(6), C = 10.606(4) Å, = 73.46(3), β = 95.00(2), γ = 73.42(3)°, V = 1682.3(10) Å 3; Cu 4I 4(CH 3CN) 2( o-ethylaniline) 2 (II), triclinic, , V = 1734.0(8) Å 3; Cu 4I 4(CH 3CN) 2(6-ethyl- o-toluidine) 2 (III), orthorhombic, Pnam, a = 14.976(6), b = 21.187(6), C = 12.545(2) Å, V = 3980.7(2) Å 3; Cu 4I 4(CH 3CN) 2( p-anisidine) 2 (IV), monoclinic, A2/ a, A = 20.032(10), B = 7.863(1), C = 18.715(9) Å, β = 101.56(4)°, V = 2888.0(2) Å 3; were examined by single crystal X-ray diffraction. Complexes I and II have no internal symmetry elements, III has an internal mirror and IV has a two-fold axis. Ab initio calculations based on the atomic positional parameters of complexes containing the three types of symmetry elements reveal HOMO orbitals to be dominated by the p orbitals of the iodine atoms whereas the LUMO orbitals contain major contributions from copper based p orbitals. 相似文献
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