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1.
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
2.
The reaction of dilithiated o-carborane ( closo-1,2-Li 2-1,2-C 2B 10H 10) with CuCl 2 gives 1,1′-bis( o-carborane) (1), 1,3′-bis( o-carborane) (2) and 1,4′-bis( o-carborane) (3). Compound 2 (C 4B 20H 22) crystallizes in the monoclinic space group P2 1/ n with A = 6.9275(6), B = 9.7655(8), C = 12.356(1) Å, β = 90.028(2)° and Z = 2. The structure was solved by direct methods and refined to R = 0.048 and Rw = 0.074. Compound 3 (C 4B 20H 22) crystallizes in the orthorhombic space group P2 12 12 1 with A = 6.8854(5), B = 12.523(1), C = 19.847(1) Å and Z = 4. The structure was solved by direct methods and refined to R = 0.078 and Rw = 0.091. The coupling reaction of dilithiated m-carborane ( closo-1,7-Li 2-1,7-C 2B 10H 10) with CuCl 2 results in the formation of 1,1′-bis( m-carborane) (4) and tetra( m-carborane) (5). 相似文献
3.
The square-planar bis chelate complexes Ni(R-sal) 2 (= bis( N-alkyl)salicylaldiminato)nickel(II)) with R = (CH 2) 2Ph (I; Ph = phenyl), (CH 2) 3Ph (II), (CH 2) 4Ph (III) and (CH 2) 2(4-hydroxyphenyl) (IV) were prepared and characterized. ComplexesII and III meet the steric requirements for intramolecular aromatic ring stacking. Stopped-flow spectrophotometry was used to study the kinetics of ligand substitution in complexesI–IV by H 2salen (= N,N′-disalicylidene-ethylenediamine) in acetone. For the substitution of the two bidentate ligands in Ni(R-sal) 2 only one step is kinetically observed which follows a second-order rate law, rate = k[H 2salen] [Ni(R-sal) 2], with k = 43.4 (I), 64.0 (II), 87.0 (III) and 49.5 (IV) M −1 s −1 at 298 K. It is found, therefore, that the size of k does not change significantly upon lengthening of the alkane chain in Ni(Ph(CH 2) nsal) 2 from n = 2 to 4 and that there is no kinetic evidence for intramolecular stacking interactions. The equilibrium constants and thermodynamic parameters for the formation of the bis adductsIII·(py) 2 and III·(MeOH) 2 in acetone are reported. 相似文献
4.
Experimental evidence is provided that selenomethionine oxide (MetSeO) is more readily reducible than its sulfur analogue, methionine sulfoxide (MetSO). Pulse radiolysis experiments reveal an efficient reaction of MetSeO with one-electron reductants, such as e -aq ( k = 1.2 × 10 10M -1s -1), CO ·-2 ( k = 5.9 × 10 8 M -1s -1) and (CH 3) 2) C ·OH ( k = 3.5 × 10 7M -1s -1), forming an intermediate selenium-nitrogen coupled zwitterionic radical with the positive charge at an intramolecularly formed Se ∴ N 2 σ/1 σ* three-electron bond, which is characterized by an optical absorption with λ max at 375 nm, and a half-life of about 70 μs. The same transient is generated upon HO · radical-induced one-electron oxidation of selenomethionine (MetSe). This radical thus constitutes the redox intermediate between the two oxidation states, MetSeO and MetSe. Time-resolved optical data further indicate sulfur-selenium interactions between the Se ∴ N transient and GSH. The Se ∴ N transient appears to play a key role in the reduction of selenomethionine oxide by glutathione. 相似文献
5.
Two novel dinuclear palladium(II) complexes, {[Pd(en)Cl] 2(bpse)}(NO 3) 2 (1) and {[Pd(en)Cl] 2 (bpsu)}(NO 3) 2 (2), (where en is ethylenediamine; bpse is bis(3-methyl-4-pyridyl) selenide; bpsu is bis(3-methyl-4-pyridyl) sulfide) have been synthesized. The complexes have been characterized by elemental analysis, IR, 1H NMR, and 13C NMR. They have been assayed for antitumor activity in vitro against the mice leukemia L1210 and the human coloadenocarcinoma HCT8 cell lines. The results show that compound 1 has a lower I.D. 50 value against the two cancer cell lines as compared to compound 2; the compounds also shows a lower I.D. 50 value than cisplatin against the HCT8 cell line, but a higher I.D. 50 value than cisplatin against the L1210 cell line. Binding studies indicate that compound 1 possibly interacts with DNA by a nonintercalative mode. Kinetics of binding of the two compounds to DNA are firstly studied using ethidium bromide as a fluorescence probe with stopped-flow spectrophotometer under pseudo-first-order condition. The stronger binding of two steps in the process of the compounds interacting with DNA are observed, and the kobs and Ea of binding of the two steps (where kobs is the observed pseudo-first-order rate constant, Ea is the observed energy of activation) are obtained. 相似文献
6.
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
7.
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
8.
The ester cleavage of R- and S-isomers N-CBZ-leucine p-nitrophenyl ester intermolecularly catalyzed by R- (a) and S-stereoisomers (b) of the Pd(II) metallacycle [Pd(C 6H 4C *HMeNMe 2)Cl(py)] (3) follows the rate expression kobs = ko + kcat [3], where the rate constants kcat equal 25.8 ± 0.4 and 7.6 ± 0.5 dm 3 mol −1 s −1 for the S- and R-ester, respectively, in the case of 3a, but are 5.7 ± 0.6 and 26.7 ± 0.5 dm 3 mol −1 s −1 for the S- and R-ester, respectively, in the case of 3b (pH 6.23 and 25°C). Thus, the best catalysis occurs when the asymmetric carbons of the leucine ester and Pd(II) complex are R and S, or S and R configured, respectively. Molecular modeling suggests that the stereoselection results from the spatial interaction between the CH 2CHMe 2 radical of the ester and the -methyl group of 3. A hydrophobic/stacking contact between the leaving 4-nitrophenolate and the coordinated pyridine also seems to play a role. Less efficient intramolecular enantioselection was observed for the hydrolysis of N-t-BOC- S-metthionine p-nitrophenyl ester with R- and S-enantiomers of [Pd(C 6H 4C*HMeNMe 2)Cl] coordinated to sulfur. 相似文献
9.
Cp #2Yb (Cp #=C 5H 4(CH 2) 2NMe 2) has been obtained by reaction of YbI 2(THF) 2 with 2 equiv. of C 5H 4(CH 2CH 2NMe 2)K in THF. The X-ray structure analysis shows a bent structure with intramolecular coordination of both nitrogen atoms to ytterbium. The reaction of C 60-fullerene with Cp #2Yb leads to the formation of the fullerenide derivative [Cp #2Yb] 2C 60, which shows an ESR signal in the solid state and in THF solution at room temperature (solid: Δ H = 50 G, G = 1.9992; solution: Δ H = 10 G, G = 2.0001) and a magnetic moment of 3.6 BM. The lutetium fullerenides CpLu(C 60)(DME) (3) and Cp *Lu(C 60)(DME)(C 6H 5CH 3) (4), (Cp = η 5−C 5H 5, Cp * = η 5−C 5Me 5), were obtained by reaction of C 60 with CpLu(C 10H 8) (DME) and Cp *Lu(C 10H 8) (DME) in toluene. Both complexes are paramagnetic (μ eff = 1.4 and 0.9 BM) and exhibit temperature-dependent ESR signals (293 K: g = 1.992 and 2.0002 respectively). 相似文献
10.
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
11.
New mixed metal complexes SrCu 2(O 2CR) 3(bdmap) 3 (R = CF 3 (1a), CH 3 (1b)) and a new dinuclear bismuth complex Bi 2(O 2CCH 3) 4(bdmap) 2(H 2O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF 2 and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi 2O 3 at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2 J = 34.0(8) cm −1. Crystal data for 1a: C 27H 51N 6O 9F 9Cu 2Sr/THF, monoclinic space group P2 1/ m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) Å 3, Z = 2; for 1b: C 27H 60N 6O 9Cu 2Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) Å 3, Z = 8; for 2: C 22H 48O 11N 4Bi 2, monoclinic space group P2 1/ c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) Å 3, Z = 4. 相似文献
12.
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
13.
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
14.
Kinetic and activation parameter data for the reactions of cct-Ru(H) 2(CO) 2(PPh 3) 2 (1) ( cct = cis, cis, trans) in THF with thiols, CO and PPh 3 to give cct-RuH(SR)(CO) 2(PPh 3) 2, Ru(CO) 3(PPh 3) 2 and Ru(CO) 2(PPh 3) 2, respectively, reveal a common, rate-determining step, the initial dissociation of H 2 from 1; the activated complex probably resembles the corresponding Ru(η 2-H 2) species. Reaction of Ru(H) 2(dppm) 2 (2) (as a cis/trans mixture, DPPM = bis(diphenylphosphino)methane) with thiols initially generated cis- and trans- RuH(SR) (dppm) 2 with a rate that depends on both the type and concentration of thiol. The higher basicity of the hydride ligands in 2 (versus 1), which is demonstrated by deuterium exchange with CD 3OD, gives rise in the thiol reaction to an initial protonation step prior to loss of H 2. A species detected in the thiol reaction is possibly [RuH(η 2-H 2 (dppm) 2] 2, the anticipated intermediate for this reaction and for the hydrogen exchange with alcohol. A longer reaction of 2 with PhCH 2SH gives solely cis-Ru(SCH 2Ph) 2(dppm) 2. 相似文献
15.
Unsymmetrical di(phosphine) ligands (dpp) 2Rop (1a, b = bis(diphenylphosphino)-2-alkyl-3-oxapropane (alkyl = methyl and ethyl)) and (dpp) 2oCy (1c = trans-2-diphenylphosphinocyclohexyl diphenylphosphinite) and their Pt(II) dichloride complexes, PtCl 2((dpp) 2mop) (2a), PtCl 2((dpp) 2eop) (2b) and PtCl 2((dpp) 2oCy) (2c), have been synthesized and characterized by NMR spectroscopy. The crystal structures of 2b and 2c show that the geometry about the platinum centers is square planar. In 2b, the metal and di(phosphine) ligand chelate ring are in a chair conformation, whereas in 2c, the chelate ring conformation is a skewed boat. Initial reaction of sodium borohydride with 2a, b, c yields the monohydride monochloride complexes PtHCl((dpp) 2mop) (5a), PtHCl((dpp) 2eop) (5b) and PtHCl((dpp) 2oCy) (5c). At longer reaction times, fluxional dimeric species are obtained, [PtH((dpp) 2mop)] 2 (4a), [PtH((dpp) 2eop)] 2 (4b) and [PtH((dpp) 2oCy)] 2 (4c),and in the case of 4c two different isomers exist. The dihydride complexes PtH 2((dpp) 2mop) (3a), PtH 2((dpp) 2eop) (3b) and PtH 2((dpp) 2oCy) (3c), are prepared by further reaction of NaBH 4 and 2. Hydrogen cycling is facile in the dihydride complexes 3a, b, c, and oxidative addition of H 2 proceeds in a pairwise manner as determined by the observation of parahydrogen induced polarization (PHIP) in the 1H NMR spectra. The reductive elimination of H 2 is also shown to be concerted by reaction of dihydride complexes with D 2. Crystal data: 2b (C 30H 32Cl 6OP 2Pt), monoclinic, space group P2 1/ c (No. 14), a = 13.7040(1), b = 11.3430(7), c = 21.3880(9) Å, β = 97.923(9)°, V = 3292.9(2) Å 3 and Z = 4; 2c (C 30H 30Cl 2OP 2Pt), monoclinic, space group P2 1 (No. 4), a = 11.7360(2), b = 8.4311(2), c = 14.2789(2) Å, β = 101.290(1)°, V = 1385.52(4) Å 3 and Z = 2. 相似文献
16.
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
17.
Kinetic results are reported for intramolecular PPh 3 substitution reactions of Mo(CO) 2(η 1-L)(PPh 3) 2(SO 2) to form Mo(CO) 2(η 2-L)(PPh 3)(SO 2) (L = DMPE = (Me) 2PC 2H 4P(Me) 2 and dppe=Ph 2PC 2H 4PPh 2) in THF solvent, and for intermolecular SO 2 substitutions in Mo(CO) 3(η 2-L)(η 2-SO 2) (L = 2,2′-bipyridine, dppe) with phosphorus ligands in CH 2Cl 2 solvent. Activation parameters for intramolecular PPh 3 substitution reactions: Δ H≠ values are 12.3 kcal/mol for dmpe and 16.7 kcal/mol for dppe; Δ S≠ values are −30.3 cal/mol K for dmpe and −16.4 cal/mol K for dppe. These results are consistent with an intramolecular associative mechanism. Substitutions of SO 2 in MO(CO) 3(η 2-L)(η 2-SO 2) complexes proceed by both dissociative and associative mechanisms. The facile associative pathways for the reactions are discussed in terms of the ability of SO 2 to accept a pair of electrons from the metal, with its bonding transformations of η 2-SO 2 to η 1-pyramidal SO 2, maintaining a stable 18-e count for the complex in its reaction transition state. The structure of Mo(CO) 2(dmpe)(PPh 3)(SO 2) was determined crystallographically: P2 1/ c, A=9.311(1), B = 16.344(2), C = 18.830(2) Å, ß=91.04(1)°, V=2865.1(7) Å 3, Z=4, R( F)=3.49%. 相似文献
18.
The reactions of complex (C 5Me 5)Ir(Cl) (CO) (Me) (1a) with cyclohexylisocyanide and phosphines (L=CyNC, PHPh 2, PMePh 2, PMe 2Ph) give the products of alkyl migratory insertion (C 5Me 5Ir(Cl) (COMe) (L), in toluence or tetrahydrofuran at 323 K or higher temperature. The phenyl analogue (C 5Me 5)Ir(Cl)(CO)(Ph) or the iodide complexes (C 5Me 5)Ir(I) (CO) (R) (R=Me, Ph_are not reactive under the same conditions. The reaction of (C 5Me 5)Ir(Cl)(CO)(Me) with PMePh 2 and PMe 2Ph in acetonitrile yields the chloride substitution product [(C 5Me 5)Ir(CO)(L)(Me)] +Cl −. Kinetic measurements for the reactions of (C 5Me 5)Ir(Cl)(CO)(Me) in toluene are first order in the iridium complex and exhibit a saturation dependence on the incoming donors L. Analysis of the data suggests a two-step process involving (i) rapid formation of a molecular complex [(C 5Me 5)Ir(Cl)(CO)(Me), (L)], in which the structure of 1a is unperturbed within the limits of spectroscopic analysis, and (ii) rate determining methyl migration. The reaction parameters are K for the pre-equilibrium step ( K = 1.5 (CyNC), 7.3 (PHPh 2), 7.1 (PMePh 2) dm 3 mol −1 at 323 K) and k2 for the slow carbon---carbon bond formation ( k2 (10 5) = 6.9 (CyNC), 1.2 (PHPh 2), 1.0 (PMePh 2) s −1 at 323 K). The activation parameters for the methyl migration step in the reaction with PMePh 2 obtained between 308 and 338 K, are Δ H≠ = 106±16 kJ mol −1 and Δ S≠ = − 14±5 J K −1 mol −1. The reaction of 1a with PMePh 2 proceeds at similar rates in tetrahydrofuran ( K = 3.7 dm 3 mol −1, k2 (10 5) = 1.2 s −1, 323 K). The crystal structure of (C 5Me 5)Ir(Cl)(COMe) (PMe 2Ph) has been determined by X-ray diffraction. C 20H 29ClOPIr: Mr = 544.1, monoclinic, P2 1/ n, A = 8.084 (2), B = 9.030(2), C = 28.715 (3) Å, β = 91.41 (3)°, Z = 4, Dc = 1.71 g cm −3, V = 2095.5 Å 3, room temperatyre, Mo K, γ = 0.71069, μ = 65.55 cm −1, F(000) = 1044, R = 0.037 for 2453 independent observed reflections. The complex shows a deformed tetrahedral coordination assuming the η 5-C 5Me 5 molecular fragment as a single coordination site. The iridium-chlorine bond is staggered with respect to two adjacent C(ring)-methyl bonds, while the Ir---P and the Ir---COMe bonds are eclipsed with respect to C(ring)-methyl bonds. 相似文献
19.
After intravenous administration of the vitamin D 3 analog, 22-oxacalcitriol (OCT), to normal rats plasma metabolites were investigated by HPLC, GC-MS and LC-MS. Five side-chain oxidation metabolites, 24 R(OH)OCT, 24 S(OH)OCT, (25 R)-26(OH)OCT, (25 S)-26(OH)OCT and 24oxoOCT, were identified by comparison with the corresponding synthetic compounds. These side-chain oxidation metabolites were similar to those of calcitriol [1,25(OH) 2 vitamin D 3] described previously. Besides these five metabolites, two unique side-chain cleavage metabolites, 20 S(OH)-hexanor-OCT and 17,20 S(OH) 2-hexanor-OCT, were identified as main metabolites in plasma by GC-MS and LC-MS using a specific chemical reaction. Our studies suggest that OCT is extensively metabolized and circulates in blood as a number of metabolites as well as unchanged OCT. This metabolism includes both unique pathways of C 23-O 22 cleavage and 17-hydroxylation, in addition to the side-chain oxidation metabolites similar to those of 1,25-(OH) 2D 3. 相似文献
20.
Kinetic studies of the addition of a wide range of tertiary phosphines and phosphites to the tropylium ring of the cation [Cr(CO) 3(η 7-C 7H 7] + (1) reveal the two-term raw, kobs = k1[PR 3] + k−1. This is consistent with the reversible equilibrium process (i) which is also confirmed from IR and 1H NMR studies. In the case of the highly basic nucleophiles PBu 3n and PEt 2Ph, the rate is dominated by the k1 term and the equilibrium lies far to the right. The first-order rate constants k1, for addition to the tropylium ring decrease markedly down the series PBu 3n>PEt 2Ph>P(4-MeOC 6H 4) 3>P(4-MeC 6H 4) 3>P(C 6H 11 3>PPh 2(4-MeC 6H 4)>PPh 3>P(2-CNC 2H 4) 3>P(OBu n) 3 (overall variation 10 4). This reactivity order parallels the decreasing electron availability at the phosphorus centres, as confirmed by the linear correlation between log k1 and the Tolman Σ χ values for the nucleophiles. Excellent Hammett and Brønsted correlations are also observed for ring addition by a range of P(4-XC 6H 4) 3 nucleophiles. The Brønsted slope, , of 0.7 conirms the major importance of basicity in determining nucleophilicity towards cation 1. Kinetic studies of the related additions of PBu 3n to the cations [M(CO) 3(η 7-C 7H 7] + (M = Mo, W) reveal the rate law, Rate = k1[M][PBu 3n, and show only a small dependence of k1 on the nature of metal (Cr>WMo; 2:1.1:1). These data, together with the associated activation parameters, support a mechanism involving direct addition ( k1) of the phosphorus nucleophiles to the tropylium ring, and are inconsistent with initial rate-determining attack at the metal centre. 相似文献
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