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1.
This paper studied the mechanism of the alkene insertion elementary step in the asymmetric hydroformylation (AHF) catalyzed by RhH(CO)2[(R,S)-Yanphos] using four alkene substrates (CH2=CH- Ph, CH2=CH-Ph-(p)-Me, CH2=CH-C(==O)OCH3 and CH2=CH-OC(=O)-Ph, abbreviated as A1-A4). Interestingly, the equatorial vertical coordination mode (A mode) with respect to the Rh center was found for AI and A2 but not for A3 and A4, although the equatorial in-plane coordination mode (E mode) was found for A1 -A4. The relative energy of the E mode of the -q2-intermediates is lower than that of the A mode. In the alkene insertion step, Path 1 is more favorable than Path 2 for this system. As for AI and A2, there could be a transformation between 2eq and 2ax.  相似文献   

2.
Although 1,1-bis(trifluoromethyl)butadiene-1,3 (1) reacts with dimethylamine with selective formation of 1,4-adduct [trans-(CF3)2CHCHCHCH2N(CH3)2], halogenation of 1 proceeds with predominant formation (>92%) of 1,2-adducts (CF3)2CCHCHXCH2X (X = Cl or Br). Electrophilic conjugated addition of “ClF” or “BrF” to 1 proceeds exclusively with the formation of 1,2-adducts (CF3)2CCHCHFCH2X (major) and (CF3)2CCHCHXCH2F (X = Cl or Br). Difluorocarbene adds selectively to CHCH2 moiety of 1 forming thermally stable vinylcyclopropane. In Diels-Alder reaction with linear or cyclic dienes (butadienes, cyclopentadiene, cyclohexadiene-1,3) and quadricyclane compound 1 behaves as dienophile providing for the reaction electron-deficient CHCH2 bond. The relative rate of cycloaddition of 1 and other fluoroolefins to quadricyclane, measured by high temperature NMR, indicates that (CF3)2CCH acts as very strong electron-withdrawing substituent. Synthetic utility of products based on 1 was also demonstrated.  相似文献   

3.
《Vibrational Spectroscopy》2006,40(1):142-147
A novel compound, (4,4′-Hbpy)2(K2Mo8O26) 1 (bpy = bipydine), was synthesized by hydrothermal method and characterized by X-ray single analysis, thermalgravimetric analysis, one-dimensional (1D) infrared spectroscopy and two-dimensional (2D) correlation infrared spectroscopy under thermal perturbation. In the compound 1, the [Mo8O26] units link to potassium ions to form layer structure, and the protonated 4,4′-bpy are linked to chains by hydrogen bonds. The 2D IR correlation spectroscopy study indicates that the intensity changes of MoO, NH and CC stretching vibration are sensitive to the temperature variation, and the intensity changes of asymmetry stretching vibration of the terminal MoO occur prior to that of terminal MoO linked by K atom. At the same time, the peaks of asymmetry stretching vibrations of the terminal MoO and the stretching vibrations of NH split into two peaks respectively in 2D IR correlation spectroscopy.  相似文献   

4.
An overview is given on synthesis and structures of new bidentate phosphaalkene ligands [(RMe2Si)2CP]2E (E = O, NR, N?) and (RMe2Si)2CPN(R′)PR′′2. Exceptional properties of these ligands, extending beyond predictable properties of phosphaalkenes are: (i) the NSi bond cleavage of [(iPrMe2Si)2CP]2NSiMe3 with AuI and RhI chloro complexes under mild conditions leading to binuclear complexes of the 6π-delocalised imidobisphosphaalkene anion [(iPrMe2Si)2CP]2N?, and (ii) the chlorotropic formation of molecular 1:2 PdII and PtII metallochloroylid complexes with novel ylid-type ligands [(RMe2Si)2CP(Cl)N(R)PR2]?, and the transformation of a P-platina-P-chloroylid complex into a C-platina phosphaalkene by intramolecular chlorosilane elimination. Properties of the heavier congeners [(RMe2Si)2CP]2E (E = S, Se, Te, PR, P?, As?) and (RMe2Si)2CPEPR′′2 (E = S, Se, Te) are also described.  相似文献   

5.
Two original dinuclear (LnYb, 3 and LnEr, 4) and one trinuclear CuIILnIIICuII (LnGd, 5) complexes derived from a polydentate non symmetrical Schiff base ligand H2L have been prepared. The ligand possesses two functions (phenol and oxime) able to coordinate the Ln ions, but structural studies (X-ray diffraction and powder X-ray diffraction) show that the CuII and LnIII ions are only bridged by the oximato (NO) pair. The missing phenoxo bridge is replaced by a surprising pseudo-bridge involving one oxygen atom of the nitrato anion linked to the Cu and Ln ions according to a η2: η1: μ mode. Although this latter contact has no role from the magnetic point of view, it introduces a large deformation of the unique bridging network. The CuYb complex 3 and the trinuclear CuGdCu complex 5 present antiferromagnetic interactions, with a JCuGd interaction equal to ?1.25 cm?1 in 5. The genuine single bridge can be considered as responsible for the antiferromagnetic character of the interaction.  相似文献   

6.
The molecular structure of caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) was determined by means of gas electron diffraction. The nozzle temperature was 185 °C. The results of MP2 and B3LYP calculations with the 6-31G7 basis set were used as supporting information. These calculations predicted that caffeine has only one conformer and some of the methyl groups perform low frequency internal rotation. The electron diffraction data were analyzed on this basis. The determined structural parameters (rg and ∠α) of caffeine are as follows: <r(NC)ring> = 1.382(3) Å; r(CC) = 1.382(←) Å; r(CC) = 1.446(18) Å; r(CN) = 1.297(11) Å; <r(NCmethyl)> = 1.459(13) Å; <r(CO)> = 1.206(5) Å; <r(CH)> = 1.085(11) Å; ∠N1C2N3 = 116.5(11)°; ∠N3C4C5 = 121. 5(13)°; ∠C4C5C6 = 122.9(10)°; ∠C4C5N7 = 104.7(14)°; ∠N9–C4=C5 = 111.6(10)°; <∠NCHmethyl> = 108.5(28)°. Angle brackets denote average values; parenthesized values are the estimated limits of error (3σ) referring to the last significant digit; left arrow in parentheses means that this parameter is bound to the preceding one.  相似文献   

7.
The reaction of RuTp(COD)Cl (1) with PR3 (PR3 = PPh2iPr, PiPr3, PPh3) and propargylic alcohols HCCCPh2OH, HCCCFc2OH (Fc = ferrocenyl), and HCCC(Ph)MeOH has been studied.In the case of PR3 = PPh2iPr, PiPr3 and HCCCPh2OH, the 3-hydroxyvinylidene complexes RuTp(PPh2iPr)(CCHC(Ph)2OH)Cl (2a) and RuTp(PiPr3)(CCHC(Ph2)OH)Cl (2b) were isolated.With PR3 = PPh2iPr and HCCCFc2OH as well as with PR3 = PPh3 and HCCCPh2OH dehydration takes place affording the allenylidene complexes RuTp(PPh2iPr)(CCCFc2)Cl (3b) and RuTp(PPh3)(CCCPh2)Cl (3c).Similarly, with PPh2iPr and HCCC(Ph)MeOH rapid elimination of water results in the formation of the vinylvinylidene complex RuTp(PPh2iPr)(CCHC(Ph)CH2)Cl (4).In contrast to the reactions of the RuTp(PR3)Cl fragment with propargylic alcohols, with HCC(CH2)nOH (n = 2, 3, 4, 5) six-, and seven-membered cyclic oxycarbene complexes RuTp(PR3)(C4H6O)Cl (5), RuTp(PR3)(C5H8O)Cl (6), and RuTp(PR3)(C6H10O)Cl (7) are obtained. On the other hand, with 1-ethynylcyclohexanol the vinylvinylidene complex RuTp(PPh2iPr)(CCHC6H9)Cl (8) is formed. The reaction of the allenylidene complexes 3ac with acid has been investigated. Addition of CF3COOH to a solution of 3ac resulted in the reversible formation of the novel RuTp vinylcarbyne complexes [RuTp(PPh2iPr)(C–CHCPh2)Cl]+ (9a), [RuTp(PPh2iPr)(C–CHCFc2)Cl]+ (9b), and [RuTp(PPh3)(C–CHCPh2)Cl]+ (9c). The structures of 3a, 3b, and 5b have been determined by X-ray crystallography.  相似文献   

8.
《Vibrational Spectroscopy》2007,43(1):104-110
The Raman spectra of serine [α-amino-β-hydroxypropionic acid; HOCH2CH(NH3)+COO] and 3,3-dideutero-serine [HOCD2CH(NH3)+COO] in aqueous solution were studied in the range 4000–300 cm−1. The data obtained for the deuterated compound are novel and provide compelling evidence that previously reported assignments for the undeuterated amino acid should be revised.  相似文献   

9.
DFT calculations with B3LYP and PBE1PBE functionals and 6–311++G(d,p) basis set have been performed in order to obtain molecular geometries, binding energies and vibrational properties of the RCN?HF H-bonded complexes with R = NH2, CH3O, CH3, OH, SH, H, Cl, F, CF3, CN and NO2. As expected, it has been verified as a red-shift of the HF stretching frequency (νHF), in conformity with the elongation of the bond after complexation. On the other hand, the CN stretching frequency (νCN) is blue-shifted and corresponds to a shortening of the bond. The binding energies (ΔEc), including BSSE and ZPVE corrections, show a linear correlation with several structural, electronic and vibrational properties. In particular, an important linear dependence between the binding energy and the calculated dipole moment of the free RCN molecule (μRCN) has been found. This result suggests that μRCN can be a useful quantity in order to predict the ability of this fragment to form a hydrogen-bond. The IR intensities of stretching and bending modes of complexed HF acid fragment are adequately interpreted through the atomic polar tensor of the hydrogen atom in HF using the modified CCFO model for infrared intensities. The new vibrational modes arising from complexation show several interesting features.  相似文献   

10.
Combined experimental and theoretical studies on molecular structure of the zero generation dendron, built from the hexafunctional cyclotriphosphazene core, with five OC6H4(CH2)2NHSO2C10H6N(CH3)2 terminal groups and one oxybenzaldehyde group G0 are reported. The Fourier transform Raman and IR spectra of G0 have been recorded. Conformations of low energy isomers of G0 have been studied at quantum-chemical level. The optimized geometry has been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. The theoretical geometrical parameters, harmonic vibrational frequencies, IR intensities and Raman scattering activities are predicted in a good agreement with the experimental data. It was found that dendron molecule G0 has a concave lens structure with planar OC6H4CHO fragments and slightly non-planar cyclotriphosphazene core. Relying on DFT calculations the bands of the core and terminal groups were assigned. The frequencies of ν(NH) bands in the IR spectrum reveal the presence of the H-bonds in the dendron.  相似文献   

11.
Three 1D bimetallic M(II)/Ni(II) (M = Cu, Zn and Cd) complexes, [Cu(OHepy)2Ni(CN)4]n (1), [Zn(OHepy)2Ni(CN)4]n (2) and [Cd(OHepy)2Ni(CN)4]n (3) (2-(2-hydroxyethyl)pyridine abbreviated to OHepy), have been synthesized and characterized by FT-IR and Raman spectroscopy, elemental, thermal analyses and single crystal X-ray diffraction techniques. FT-IR and Raman spectra of OHepy have been experimentally and theoretically investigated in the region of 4000–250 cm−1. The corresponding vibrational assignments of OHepy are examined by means of B3LYP hybrid density functional theory (DFT) method together with 6-311++G(d, p) basis set. Moreover, reliable vibrational assignments have been made on the basis of potential energy distribution (PED). The structures of the complexes consist of one-dimensional polymeric chain M(OHepy)2NCNi(CN)2CNM(OHepy)2−, in which the M(II) and Ni(II) atoms are linked by CN groups. The nickel atom is fourfold coordinated with four cyanide-carbon atoms in a square planar arrangement and the metal(II) atoms are sixfold coordinated with two cyanide nitrogen, two OHepy nitrogen and two OHepy oxygen atoms, in a distorted octahedral arrangement. In all the complexes adjacent chains are connected by π⋯π, CH⋯Ni and OH⋯N hydrogen bonding interactions to form two and three dimensional networks.  相似文献   

12.
《Comptes Rendus Chimie》2016,19(3):320-332
1,3-dipolar cycloaddition of diaryldiazomethanes Ar2CN2 across Cl3C–CHN–CO2Et 1 yields Δ3-1,2,4-triazolines 2. Thermolysis of 2 leads, via transient azomethine ylides 3, to diaryldichloroazabutadienes [Ar(Ar')CN–CHCCl2] 4. Treatment of 4a (Ar = Ar' = C6H5) and 4c (Ar = Ar' = p-ClC6H4) with NaSR in DMF yields 2-azabutadienes [Ar2CN–C(H)C(SR)2] 5. In contrast, nucleophilic attack of NaStBu on 4 affords azadienic dithioethers [Ar2CN–C(StBu)C(H)(StBu)] (7a Ar = C6H5; 7b Ar' = p-ClC6H4). The reaction of 4a with NaSEt conducted in neat EtSH produces [Ph2CN–C(H)(SEt)–CCl2H] 8, which after dehydrochloration by NaOMe and subsequent addition of NaSEt is converted to [Ph2CN–C(SEt)C(H)(SEt)] 7c. Upon the reaction of 4c with NaSiPr, the intermediate dithioether [(p-ClC6H4)2CN–CHC(SiPr)2] 5k is converted to tetrakisthioether [(p-iPrSC6H4)2CN–CHC(SiPr)2] 6. Treatment of 4a with the sodium salt of piperidine leads to [Ph2CN–CHC(NC5H10)2] 10. The coordination of 6 on CuBr affords the macrocyclic dinuclear Cu(I) complex 11. The crystal structures of 5i, 7a,b, 10 and 11 have been determined by X-ray diffraction.  相似文献   

13.
《Polyhedron》2007,26(5):981-988
New π-conjugated butadiynyl ligand FcC(CH3)2Fc′–CC–CC–Ph (L1) has been synthesized and its reaction with Co2(CO)8 has been studied. New clusters [FcC(CH3)2Fc′–CC–CC–Ph][Co2(CO)6]n [(1): n = 1; (2): n = 2] and [Fc–CC–CC–Ph][Co2(CO)6]n [(3): n =  1; (4): n = 2] were obtained by the reaction of ligands FcC(CH3)2Fc′–CC–CC–Ph (L1) and Fc–CC–CC–Ph (L2) with Co2(CO)8 respectively and the composition and structure of the clusters and ligands have been characterized by elemental analysis, FTIR, 1H and 13C NMR and MS. The crystal structures of compounds L1, L2, 2 and 4 have been determined by X-ray single crystal analysis.  相似文献   

14.
KOH activation of petroleum coke (PC) was conducted with 30 vol%H2 + 70 vol% N2 as carrier gas. TG-DTG, FTIR, elemental analysis, N2 adsorption, GC and XRD techniques were used to investigate the effects of hydrogen on the activation. During the initial stage of the activation, i.e. the carbonization of the PC, additional CH and CH2 species were formed due to the chemisorption of hydrogen on the nascent sites of the PC created by the removal of the surface heteroatom groups. The formation of the CH and CH2 species increased the quantity of ‘active sites’ which is favorable to the further activation reaction, and developed the porous structure of the activated carbons. The micropore volume and BET surface areas of the activated carbon prepared under 30 vol% H2 + 70 vol% N2 and with a relatively low KOH/PC weight ratio of 2:1 have been increased from 0.78 cm3/g and 1936 m2/g to 0.97 cm3/g and 2477 m2/g, respectively, compared to that prepared in pure N2 atmosphere with the same KOH/PC ratio.  相似文献   

15.
《Polyhedron》1987,6(5):881-889
The crystal structures of diaquabis[(benzylthio)acetato]zinc(II), [Zn(BTA)2 (H2O)2] (1), catena-[diaqua-tetra[(benzylthio)acetato)]-bis[cadmium(II)], [Cd2(BTA)4 H2O)2]n (2), catena-{tetra-μ-[2-methyl-3-(phenylthio)propionato-O,O′]-bis[copper (II)]}, [Cu2(MPTP)4]n (3) and tetra-μ-[2-methyl-2-(phenylthio)propionato-O,O′]- bis[ethanol copper(II)], [Cu2(PTIBA)4(EtOH)2] (4) have been determined using X-ray diffraction techniques. Complex (1) is monomeric with distorted octahedral stereochemistry and lies on a two-fold rotational axis. The MO6 coordination involves four oxygens from two slightly asymmetric bidentate BTA car☐yl groups [ZnO, 2.138(3), 2.28(3)Å] and two cis-related waters [ZnOw, 1.996(3)Å]. The cadmium complex (2) is best described in terms of a polymer with the repeating unit consisting of two different centres, one seven, the other six-coordinate. With the first, the distorted MO6S coordination sphere has four oxygens from two asymmetric bidentate car☐ylate groups (ligands B and C) [CdO, 2.36, 2.56(1)Å; 2.26, 2.67(1)Å], an oxygen and a sulphur from a bidentate chelate ligand (A) [CdO, 2.36(1)Å; CdS, 2.773(4)Å] and an oxygen from a bridging car☐yl group (ligand D) [CdO, 2.28(1)Å]. Ligands C and D also bridge two Cd centres through sulphurs [CdS, 2.739, 2.723(4)Å]. The second car☐yl oxygen of ligand A also forms a bridge to the second Cd [(CdO, 2.30(1)Å], while the distorted octahedral MO4S2 stereochemistry is completed by two waters [CdO, 2.25(1), 2.49(1)Å] and a sulphur from ligand D [CdS, 2.723(4)Å] giving a polymer structure. Complexes (3) and (4) are centrosymmetric tetra-car☐ylate bridged dimers [for (3) Cu ··· Cu, 2.586(3)Å; mean CuO(equatorial), 1.957(11)Å; for the two independent dimers in (4), Cu ··· Cu, 2.596(1), 2.616(1)Å; CuO (equatorial), 1.952(4), 1.968(4)Åmean]. The axial positions of the dimer in (3) are occupied by car☐yl oxygens of adjacent dimers [CuO, 2.280(9)Å] forming a polymer structure. In contrast, these positions in (4) are occupied by ethanol molecules with CuO, 2.222(3) and 2.177(4)Årespectively for the two independent dimers.  相似文献   

16.
Continuous gradient temperature Raman spectroscopy (GTRS) applies the temperature gradients utilized in differential scanning calorimetry (DSC) to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur near phase transitions. Herein we apply GTRS and DSC to the solid dipeptides Ala-Pro, Pro-Ala, and the mixture Ala-Pro/Pro-Ala 2:1. A simple change in residue order resulted in dramatic changes in thermal stability and properties. Characteristic Pro vibrations were observed at ∼75 °C higher temperature in Pro-Ala than Ala-Pro. The appearance/disappearance of characteristic vibrational modes with increasing temperature showed that a double peak in the Ala-Pro major phase transition (174–184 °C) was due to a gauche to anti 165° rotation of H3CC*NH3 about C*. CH2 rocking and wagging frequencies present in Pro-Ala were not observed in Ala-Pro. For Ala-Pro, the Ala +NH3, and Pro COO sites were flexible whereas the Pro ring moiety was not; since the OCN (C)2 amide bond is planar the CNC moiety keeps the Pro ring rigid. For Pro-Ala, CH2 sites in the Pro ring were flexible and the OCNH amide bond is perpendicular to the Pro ring. Since the mass of the Pro ring is significantly larger than the mass of the flexible Ala +NH3 moiety, Pro-Ala absorbs more thermal energy, corresponding to a higher phase transition temperature (240–260 °C). Ala-Pro, Pro-Ala, and Ala-Pro/Pro-Ala 2:1 exhibited α-helix, β-sheet, α-helix secondary structure conformations, respectively.  相似文献   

17.
The curing dynamics and network formation of cyanate ester resin/graphene oxide (GO) nanocomposites were studied by means of Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FT-IR) and Raman spectroscopies. The incorporation of GO into the resin showed a strong catalytic effect on the cure of the resin, especially in the initial stages. Addition of 4 wt.% GO resulted in the decrease of curing temperature significantly about 97 °C. Activation energy of the nanocomposites also maintained at a low level till the end of the cure. The most effective catalytic behavior was observed with 1 wt.% GO. Both FT-IR and Raman spectra revealed that OH group in GO reacted with cyanate group OCN in the resin to form O(CNH)O bond in the early stages of the cure. These results could provide a low temperature curing route for cyanate ester resins with improved curing efficiency.  相似文献   

18.
《Comptes Rendus Chimie》2015,18(12):1277-1283
A theoretical study of the [3+2] cycloaddition (32CA) reaction between benzonitrile sulfide BNS1 and trichloroacetonitrile TCAN2 at the MPWB1 K/6-311G(d) level was undertaken. Among two feasible C1N5 and C1C4 regioisomeric channels, the former is completely preferred, in the presence of toluene, over the latter, both kinetically, ΔΔGactivation = 17.5 kcal/mol, and thermodynamically, ΔΔGreaction = –12.8 kcal/mol, in excellent agreement with experimental outcomes. The strong global electrophilic and nucleophilic characters found for TCAN2 and BNS1, respectively, allow the studied 32CA reaction to take place via a polar process. Interestingly, the analysis of the TSs geometries clarifies that in the case under study, regioselectivity is controlled by destabilizing steric repulsion interactions rather than electronic ones. The ELF topological patterns indicate that while the formation of S3C4 single bond takes place exactly according to Domingo's model, that of the C1N5 single bond is a direct consequence of the nucleophilic attack of the C5 carbon atom on the N5 nitrogen atom supporting a two-stage one-step molecular mechanism.  相似文献   

19.
The mechanism of Rh(Ⅱ)carbene S-H insertion into H_2S in gas phase has been studied by B3LYP functional.Calculation results showed that the Rh(Ⅱ)carbene S-H insertion into H_2S took only stepwise channels and no concerted channels had been located, which was different from the Rh(Ⅱ)carbene C-H and O-H insertions.  相似文献   

20.
A computational study at different levels of theory was performed for the not yet synthesized phosphastannaallenes >SnCP– in order to evaluate the strength of the SnC bond, the main postulated factor to stabilize such species, and the geometry in R2SnCPR derivatives. The influence of the substituents with various electronic effects (H, Me, Ph, F, Cl, OMe, SiMe3) at the Sn or P atoms of the SnCP unit on the SnC bond order was evaluated in the quest for a substituent that would stabilize the phosphastannaallenic unit. PC bond orders have also been calculated.  相似文献   

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