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1.
The complex [Et 4N][W(CO) 5OMe] (1) has been prepared from the reaction of the photochemically generated W(CO) 5THF adduct and [Et 4N][OH] in methanol. Complex 1 was shown to undergo rapid CO dissociation in THF to quantitatively provide the dimeric dianion, [W(CO) 4OMe] 22−. The resulting THF insoluble salt [Et 4N] 2[W(CO) 4OMe] 2 (2) has been structurally characterized by X-ray crystallography, with the doubly bridging methoxide ligands being in an anti configuration. Complex 2 was found to subsequently react with excess methoxide ligand in a THF slurry to afford the face-sharing octahedron complex [Et 4N] 3[W 2(CO) 6(OMe) 3] (3) which contains three doubly bridging methoxide groups. In the absence of excess methoxide ligand complex 2 cleanly yields the tetrameric complex [Et 4N] 4[W(CO) 3OMe] 4 (4) which has been structurally characterized as a cubane-like arrangement with triply bridging μ3-methoxide groups and W(CO) 3 units. Although complex 3 was not characterized in the solid state, the closely related glycolate derivative [Et 4N] 3[W 2(CO) 6(OCH 2CH 2OH) 3] (5) was synthesized and its structure determined by X-ray crystallography. The trianions of complex 5 are linked in the crystal lattice by strong intermolecular hydrogen bonds. Crystal data for 2: space group P2 1/ n, a = 7.696(2), b = 22.019(4), c = 9.714(2) Å, β = 92.22(3)°, Z = 4, R = 6.43%. Crystal data for 4: space group Fddd, a = 12.433(9), b = 24.01(2), c = 39.29(3) Å, Z = 8, R = 8.13%. Crystal data for 5: space group P2 12 12 1, a = 11.43(2), b = 12.91(1), c = 29.85(6) Å, Z = 8, R = 8.29%. Finally, the rate of CO ligand dissociation in the closely related aryloxide derivatives [Et 4N][W(CO) 5OR] (R = C 6H 5 and 3,5-F 2C 6H 3) were measured to be 2.15 × 10 −2 and 1.31 × 10 −3 s −1, respectively, in THF solution at 5°C. Hence, the value of the rate constant of 2.15 × 10 −2 s −1 establishes a lower limit for the first-order rate constant for CO loss in the W(CO) 5OMe − anion, since the methoxide ligand is a better π-donating group than phenoxide. 相似文献
2.
Rates of stepwise anation of cis-Cr(ox) 2(H 2O 2) − with SCN −/N 3−, Cr(acac) 2(H 2O) 2+ with SCN − and Cr(atda)(H 2O) 2 with SCN − have been investigated in weakly acidic aqueous solutions. Rate constants, kI and kII for the two steps in each system, are composite as kx = kx0+ kxX[X −] ( x = I, II; X − = SCN −, N 3−). These rate constants have been evaluated also as the corresponding Δ H≠ and Δ S≠ values. The results obtained and the plausible I d mechanism seem to suggest Cr---OOC bond dissociation (hence a strongly negative Δ S≠) generating the transition state in each system with outer-sphere association forming the precursor complex in the X − dependent paths. 相似文献
3.
The positive ion electrospray mass spectrometry (ESI-MS) of trans-[Ru(NO)Cl)(dpaH) 2]Cl 2 (dpaH=2,2′-dipyridylamine), obtained from the carrier solvent of H 2O–CH 3OH (50:50), revealed 1+ ions of the formulas [Ru II(NO +)Cl(dpaH)(dpa)] + ( m/ z=508), [Ru IIICl(dpaH)(dpa −)] + ( m/ z=478), [Ru II(NO +)(dpa) 2] + ( m/ z=472), [Ru III(dpa) 2] + ( m/ z=442), originating from proton dissociation from the parent [Ru II(NO +)Cl(dpaH) 2] 2+ ion with subsequent loss of NO (17.4% of dissociative events) or loss of HCl (82.6% of dissociative events). Further loss of NO from the m/ z=472 fragment yields the m/ z=442 fragment. Thus, ionization of the NH moiety of dpaH is a significant factor in controlling the net ionic charge in the gas phase, and allowing preferential dissociation of HCl in the fragmentation processes. With NaCl added, an ion pair, {Na[Ru II(NO)Cl(dpa) 2]} + ( m/ z=530; 532), is detectable. All these positive mass peaks that contain Ru carry a signature ‘handprint’ of adjacent m/ z peaks due to the isotopic distribution of 104Ru, 102Ru, 101Ru, 99Ru, 98Ru and 96Ru mass centered around 101Ru for each fragment, and have been matched to the theoretical isotopic distribution for each set of peaks centered on the main isotope peak. When the starting complex is allowed to undergo aquation for two weeks in H 2O, loss of the axial Cl − is shown by the approximately 77% attenuation of the [Ru II(NO +)Cl(dpaH)(dpa)] + ion, being replaced by the [Ru II(NO +)(H 2O)(dpa) 2] + ( m/ z=490) as the most abundant high-mass species. Loss of H 2O is observed to form [Ru II(NO +)(dpa) 2] + ( m/ z=472). No positive ion mass spectral peaks were observed for RuCl 3(NO)(H 2O) 2, ‘caged NO’. Negative ions were observed by proton dissociation forming [Ru II(NO)Cl 3(H 2O)(OH)] − in the ionization chamber, detecting the parent 1− ion at m/ z=274, followed by the loss of NO as the main dissociative pathway that produces [Ru IIICl 3(H 2O)(OH)] − ( m/ z=244). This species undergoes reductive elimination of a chlorine atom, forming [Ru IICl 2(H 2O)(OH)] − ( m/ z=208). The ease of the NO dissociation is increased for the negative ions, which should be more able to stabilize a Ru III product upon NO loss. 相似文献
4.
Ring segments of rat middle cerebral artery (MCA) were prepared for measurement of isometric force and precontracted with 10 −4 M uridine triphosphate (UTP). Concentration-effect curves (CEC) were constructed for bradykinin (BK, 10 −8–10 −5 M) in segments with functionally intect (E+) or denuded (E−) endothelium. E− segments did not dilate to BK. The BK receptor was characterized by application of specific B 1 or B 2 antagonists [des-Arg 9-Leu 8] BK (10 −5 M) and [
-Arg 0-Hyp 3-Thi 5-
-Tic 7-Oic 8] BK (HOE140,3 × 10 −7 M), respectively, or B 1 agonist [des-Arg 9] BK (10 −8–10 −4 M). Involvement of nitric oxide (NO) was tested with NG-nitro-
-arginine (LNNA, 10 −4 M). BK induced concentration-dependent relaxation with a maximal effect ( Emax) of 40.86 ± 1.50% at 10 −6 M and a pD 2 (−log 10 EC 50) of 6.818 ± 0.044. This relaxation could be prevented with HOE140 or LNNA, but was not influenced by [des-Arg 9-Leu 8] BK. [des-Arg 9] BK did not induce any effect. These results demonstrate that BK induced relaxation via endothelial B 2 receptors and release of NO in isolated rat MCA. 相似文献
5.
The reaction of meso-tetrakis (4-dimethoxyphenyl) porphinatomanganese(II), MnTP OMeP, with TCNE (TCNE = tetracyanoethylene) leads to the formation of [MnTP OMeP] + [TCNE] − and [MnTP OMeP] +[OC(CN)C(CN) 2] −. The single-crystal X-ray structures of the latter as well as [Cu(bipy) 2Cl] + [OC(CN)C(CN) 2] − were determined. The former has a disordered [OC(CN)C(CN) 2] − bridging via C and O between a pair of Mn III sites, whereas the latter has an isolated [OC(CN)C(CN) 2] − unbound to Cu II. The IR characterization for μ 2-C,O bound [OC(CN)C(CN) 2] − is at 2219m and 2196s (νCN) cm −1 and at 1558s (νCO) cm −1 while for unbound [OC(CN)C(CN) 2] − it is at 2210m, 2203m, 2181m (νCN) cm −1 and at 1583s (νCO) cm −1. 相似文献
6.
A study of the reactions of purine and pyrimidine bases has been initiated with the V(IV) complex [V(O)(acac) 2]. Two distinct modes of reaction have been recognized depending on the nature of the base. Simple adduct formation occurs when the base contains a sufficiently basic lone pair, but when bases contain acidic protons bound to nitrogen (inosine, thymine), cleavage of one acetylacetonate ligand occurs to give potentially polymeric species. This behavior is in contrast to that of the inert [Co(NO 2) 2(acac) 2] − ion. 相似文献
7.
The complex [Ru(SB 12H 11)(NH 3) 5]·2H 2O has been prepared by the reaction of Cs 2B 12H 11SH with [RuCl(NH 3) 5]Cl 2 in aqueous solution. The complex represents the first reported example of the borocaptate anion acting as a ligand. The structure of the complex has been determined by single crystal X-ray diffraction analysis. The crystal parameters are monoclinic, space group P2 1/ c, A = 8.056(1), B = 14.240(2), C = 15.172(2) Å, β=98.48° and Z = 4. The ruthenium atom has a distorted octahedral coordination. The distortion is probably due to the high (3 −) charge and the large bulk of the borocaptate ligand. These features can also be observed in the spectroscopic properties of the complex. 相似文献
8.
[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
9.
Oxygenation of [Cu II(fla)(idpa)]ClO 4 (fla=flavonolate; IDPA=3,3′-iminobis( N, N-dimethylpropylamine)) in dimethylformamide gives [Cu II(idpa)( O-bs)]ClO 4 ( O-bs= O-benzoylsalicylate) and CO. The oxygenolysis of [Cu II(fla)(idpa)]ClO 4 in DMF was followed by electronic spectroscopy and the rate law −d[{Cu II(fla)(idpa)}ClO 4]/d t= kobs[{Cu II(fla)(idpa)}ClO 4][O 2] was obtained. The rate constant, activation enthalpy and entropy at 373 K are kobs=6.13±0.16×10 −3 M −1 s −1, Δ H‡=64±5 kJ mol −1, Δ S‡=−120±13 J mol −1 K −1, respectively. The reaction fits a Hammett linear free energy relationship and a higher electron density on copper gives faster oxygenation rates. The complex [Cu II(fla)(idpa)]ClO 4 has also been found to be a selective catalyst for the oxygenation of flavonol to the corresponding O-benzoylsalicylic acid and CO. The kinetics of the oxygenolysis in DMF was followed by electronic spectroscopy and the following rate law was obtained: −d[flaH]/d t= kobs[{Cu II(fla)(idpa)}ClO 4][O 2]. The rate constant, activation enthalpy and entropy at 403 K are kobs=4.22±0.15×10 −2 M −1 s −1, Δ H‡=71±6 kJ mol −1, Δ S‡=−97±15 J mol −1 K −1, respectively. 相似文献
10.
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
11.
[NBu n4] 2[W(C 3Se 5) 3] (C 3Se 52− = 1,3-diselenole-2-selone-4,5- diselenolate(2−)) was prepared by the reaction of Na 2[C 3Se 5] with WCl 6 in ethanol, followed by addition of [NBu n4]Br. The cyclic voltammogram in dichloromethane exhibits two oxidation peaks at −0.04 and +0.03 V (versus SCE). The complex reacted with [Fe(C 5Me 5) 2][BF 4], iodine or [TTF] 3[BF 4] 2 (TTF ·+ = the tetrathiafulvalenium radical cation) in acetonitrile to afford the oxidized complexes [Fe(C 5Me 5) 2] 0.5[W(C 3Se 5) 3], [NBu n4] 0.1[W(C 3Se 5) 3] and [TTF] 0.5[W(C 3Se 5) 3], respectively. Current-controlled electrochemical oxidation of the complex in acetonitrile gave [NBu n4] 0.6[W(C 3Se 5) 3]. The oxidized complexes exhibit electrical conductivities of 4.7×10 −5−1.5×10 −3 S cm −1 at room temperature measured for compacted pellets. Electronic absorption, IR and ESR spectra of these complexes are discussed. 相似文献
12.
1. Cyanide causes a slow disappearance of the oxidized band (648 nm) of cytochrome d in particles of Azotobacter vinelandii and inhibits the appearance of the reduced band (631 nm). No effect of cyanide is found on the reduced band of cytochrome d. 2. The kinetics of the disappearance of the 648-nm band of cytochrome d with excess cyanide deviates from first-order kinetics at lower temperatures (22 °C) indicating that at least two conformations of the enzyme are involved. At higher temperatures (32 °C) the observed kinetics of the cyanide reaction are first order with a kon = 0.7 M−1·s−1 and with an estimated koff of approximately 5·10−5 s−1. 3. The value of the koff (7·10−4−14·10−4 s−1 at 32 °C) determined from the rate of reduction of cyanocytochrome d by Na2S2O4 or NADH is one order of magnitude larger than the koff value found when the enzyme is in its oxidized state. 4. No effect of cyanide is found on the spectrum of cytochrome a1. 相似文献
13.
The rates of displacement of dimethyl sulfoxide from the cation [Pt(phen) (CH 3) (Me 2SO)] + by a series of uncharged and negatively charged nucleophiles have been measured in a methanol/water (19:1 vol./vol.) mixture. The starting complex and the reaction products were characterized either as solids or in solution by their IR and 1H NMR spectra. The substitution reactions take place by way of a direct bimolecular attack of the ligand on the substrate. The sequence of reactivity observed is as expected on the basis of a nucleophilicity scale relevant for + 1 charged substrates ([Pt(en) (NH 3)Cl] + used as standard). The difference of reactivity between the first (t-BuNH 2) and the last (SeCN −) members of the series spans five orders of magnitude. The value measured for the nucleophilic discrimination (1.55) is the highest found so far for cationic substrates. This is a result of the easy transfer of some of the electron density brought in by the incoming ligand into the ancillary ligands. When the reaction is carried out in a series of protic and dipolar aprotic solvents, using chloride ion as nucleophile, the rate of formation of [Pt (phen) (CH 3)Cl] is dominated by the extent of solvation of Cl −, as measured by its values of the Gibbs molar energy of transfer Δ tG0. Conductivity measurements at 25°C in dichloromethane were fitted to the Fuoss equation and the values of the dissociation constants Kd for the ion pairs were calculated as follows: 2.27 × 10 −5 M for Bu 4NCl, 2.75 × 10 −5 M for Bu 4NSCN and 17.05 × 10 −5 M for [Pt(phen) (CH 3) (Me 2SO)]PF 6. The pseudo-first-order rate constants kobs for the reactions with Bu 4NCl, Bu 4NBr, Bu 4NSCN and Bu 4NI showed a curvilinear dependence on the concentration of the salt which levels off very soon (at concentrations higher than 0.005 M the kinetics are zero order in [Bu 4NX]). On addition of the inert electrolyte Bu 4NPF 6 the rates slow down and the kinetics follow the rate law kobs = kKip[Bu 4NX]/[Bu 4NPF 6] + Kip[Bu 4NX]). These findings fit well with a reaction scheme which involves a pre-equilibrium Kip between ion pairs, followed by unimolecular substitution within the contact ion pair [Pt(phen) (CH 3) (Me 2SO)X] ip. Values of the equilibrium constants Kip for ion-pair exchange and of the internal substitution rates k were derived. The latter showed that the discrimination in reactivity between Cl −, Br −, SCN − and I − is greatly reduced with respect to aqueous solutions. The reason behind this may be desolvation of the ions coupled to the fact that a contact ion pair is already at a certain distance along the reaction coordinate in the direction of the transition state. Applications of the special salt effect and of ion pairing to synthesis are discussed. 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.
A method for determination of carboxymethyl cellulose (CMC) molecular weight ( MW) and chemical heterogeneity (degree of oxidation (DO)) using a bi-detector HPSEC (UV-detector online with refractometer) has been developed. It has been found that the use of 0.5 N NaOH or 0.4 M acetate buffer as the eluent ensures CMC separation according to MW. It has been revealed that the universal calibration for the polyelectrolyte CMC and the neutral polymer dextran is valid under the conditions applied. The Mark–Houwink equations for CMC in 0.5 N NaOH and 0.4 M acetate buffer have been estimated to be [ η]=5.37×10 −4 MW0.73 and [ η] =2.24×10 −4 MW0.83 dl g −1, respectively. The equation log K=1.64−4.00 ml g −1 for CMC has been estimated. An approach for determining DO from adsorption at 290 or 313 nm has been developed. 相似文献
16.
The mechanisms of cholinergic stimulation of gastrin cells were studied in the rat pancreatic cell line B6 RIN. Carbachol induced an increase in intracellular Ca 2+ and stimulated gastrin release in a dose-dependent manner over the range 10 −5-10 −3 M. These effects were completely abolished by atropine, suggesting the implication of muscarinic cholinergic receptors. The binding properties of these receptors were investigated. [ N-Methyl- 3H]scopolamine ([ 3h]nms) binding on cell homogenates was time-dependent, saturable and consistent with a single high-affinity binding class ( Kd = 39.5 pM, and Bmax = 7.9 fmol/ mg DNA). Carbachol competitively inhibited [ 3H]NMS binding. The potency of inhibition of [ 3H]NMS binding by subtype selective antagonists was hexahydrodifenidol> pirenzepine> AF-DX 116. These results suggest the M 3, muscarinic receptors may be involved in the carbachol-induced gastrin release from B6 RIN cells. 相似文献
17.
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
18.
Dinuclear manganese(II) complexes [Mn 2(bomp)(PhCO 2) 2]BPh 4 (1), [Mn 2(bomp)(MeCO 2) 2]BPh 4 (2), and [Mn 2(bomp)(PhCO 2) 2]PF 6 (3) were synthesized with a dinucleating ligand 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol [H(bomp)]. Dinuclear zinc complex [Zn 2(bomp)(PhCO 2) 2]PF 6 (4) was also synthesized for the purpose of comparison. X-ray analysis revealed that the complex 1·CHCl 3 contains two manganese ions bridged by the phenolic oxygen and two benzoate groups, forming a μ-phenoxo-bis(μ-benzoato)dimanganese(II) core. Magnetic susceptibility measurements of 1–3 over the temperature range 1.8–300 K indicated antiferromagnetic interaction ( J=−4 to −6 cm −1). Cyclic voltammograms of 3 showed a quasi-reversible oxidation process at +0.9 V versus a saturated sodium chloride calomel reference electrode, assigned to Mn IIMn II/Mn IIMn III. 相似文献
19.
The kinetics of substitution reactions of [η-CpFe(CO) 3]PF 6 with PPh 3 in the presence of R-PyOs have been studied. For all the R-PyOs (R = 4-OMe, 4-Me, 3,4-(CH) 4, 4-Ph, 3-Me, 2,3-(CH) 4, 2,6-Me 2, 2-Me), the reactions yeild the same product [η 5-CpFe(CO) 2PPh 3]PF 6, according to a second-order rate law that is first order in concentrations of [η 5-CpFe(CO) 3]PF 6 and of R-PyO but zero order in PPh 3 concentration. These results, along with the dependence of the reaction rate on the nature of R-PyO, are consistent with an associative mechanism. Activation parameters further support the bimmolecular nature of the reactions: Δ H≠ = 13.4 ± 0.4 kcal mol −1, Δ S≠ = −19.1 ± 1.3 cal k −1 mol −1 for 4-PhPyO; Δ H≠ = 12.3 ± 0.3 kcal mol −1, Δ S≠ = 24.7 ±1.0 cal K −1 mol −1 for 2-MePyO. For the various substituted pyridine N-oxides studied in this paper, the rates of reaction increase with the increasing electron-donating abilities of the substituents on the pyridine ring or N-oxide basicities, but decrease with increasing 17O chemical shifts of the N-oxides. Electronic and steric factors contributing to the reactivity of pyridine N-oxides have been quantitatively assessed. 相似文献
20.
The fluoro-hydrido-oxo complex [Re(F)(H)(O)Cyttp] + (3, Cyttp = PhP(CH 2CH 2CH 2PCy 2) 2) was prepared in high yield from [Re(H 2)H 4Cyttp]SbF 6 (1(SbF 6), NaSbF 6 and acetone in toluene at reflux. Reaction chemistry of 3 has been studied and, where appropriate, compared with that of the related dihydrido-oxo complex [ReH 2(O)Cyttp] + (2). Unlike 2, which readily reacts with both CO and SO 2, 3 was found to be inert to these reagents under comparable conditions. However, 3(SbF 6) reacts with NaSbF 6 at elevated temperature to afford the difluoro-oxo complex [ReF 2(O)Cyttp] + (4). 4 undergoes fluoride substitution by Cl − or Br − to yield [Re(X)(F)(O)Cyttp] + (X = Cl (5, Br (6)). 5 can also be obtained by treatment of 6(BPh 4) with LiCl. All of these complexes contain mer-Cyttp, and 3–6 contain trans fluoride and oxide ligands as inferred from spectroscopic data. 相似文献
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