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1.
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   

2.
The structures and stability of the designed PNP pincer amido M(NO)2(PNP) and amino HM(NO)2(PNHP) complexes [M = V, Nb, and Ta, PNP = N(CH2CH2P(isopropyl)2)2, PNHP = HN(CH2CH2P(isopropyl)2)2] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H2 environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-CN, Ph-CHNH, Ph-CHNH-Ph, Ph-CHNCH2Ph, Ph-CCH, Ph-CHCH2, Ph-CHO, and Ph-COCH3, the reaction prefers either a two-step or one-step mechanism for the hydridic MH and protonic NH transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges.  相似文献   

3.
《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   

4.
Visible-light photolysis of the cheap starting material [FeCp(η6-toluene)][PF6] (Cpη5-C5H5) using a simple 100-W globe in the presence of diphenyldiphosphinoethane (dppe) and terminal alkynes cleanly yields the vinylidene complexes [FeCp(dppe)(CCHR)][PF6] and, upon further deprotonation, the iron-alkynyl complexes; the reaction is extended to ferrocenylacetylene to yield a bimetallic complex.  相似文献   

5.
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   

6.
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   

7.
In this study, alumina-supported NiMo catalysts were carburized to obtain alumina-supported nickel–molybdenum carbides as potential catalysts for dry reforming of methane. The typical carbide was compared with a low carburized material (in 5% H2/CH4) and a reduced NiMo catalyst. It was shown that the passivated alumina-supported NiMo catalysts by carbon lead to higher reactivity, selectivity, and stability for dry methane reforming reaction.  相似文献   

8.
《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   

9.
Treatment of the complex [Ru{C(CCPh)CHPh}Cl(CO)(PPh3)2] (1) with one equivalent of CNR(R =tBu, C6H3Me2-2,6) gives [Ru{C(CCPh)CHPh}Cl(CNR)(CO)(PPh3)2]. Addition of a further equivalent of isonitrile and [NH4]PF6 leads to the salts [Ru{C(CCPh)CHPh}Cl(CNR)2(CO)(PPh3)2]PF6 and the mixed species [Ru{C(CCPh) CHPh}(CO)(CNtBu)(CNC6H3Me2-2,6)(PPh3)2]PF6. The related [Ru{C(CCPh)CHPh}(CNt(CO)2  相似文献   

10.
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   

11.
A set of small radicals SiF, SiCl, F–CO, CN–O, O3H, NO3, CH2NC, CF3O, and O3 exhibit pronounced discrepancies between different experimental as well as experimental and calculated values of the respective enthalpies of formation ΔfHo(298.15). For stable molecules, this quantity is well established and reliable values are available. However, for free radicals and other short-lived intermediates, the situation is not nearly as favorable. Consequently, critical evaluation of thermodynamic properties of free radicals is necessary, both originating from experiment and computation. Calculated enthalpies of formation for the above systems are based on the ab initio methods G3MP2B3 and CCSD(T)–CBS (W1U) for which mean absolute deviations are known.  相似文献   

12.
In this work, both the intermolecular and intramolecular hydrogen bonding of 3-aminophthalimide (3AP) dimer complex in the electronically excited state have been investigated theoretically using the time-dependent density functional theory (TDDFT) method. The calculated infrared spectrum of the hydrogen-bonded 3AP dimer complex for the S1 state shows that the CO and H–N bonds involved in the intramolecular hydrogen bond C3O5?H8–N6 and intermolecular hydrogen bond C1O4?H7′–N2′ which are markedly red-shifted compared with those predicted for the ground state. The calculated length of the two hydrogen bonds C3O5?H8–N6 and C1O4?H7′–N2′ are significantly shorter in S1 state than in the ground state. However, the bond lengths of the intramolecular hydrogen bond C3′O5?H8′–N6′ and intermolecular hydrogen bond C1′O4′?H7–N2 nearly unchanged upon electronic excitation to the S1 state. Thus, the intramolecular hydrogen bond C3O5?H8–N6 and intermolecular hydrogen bond C1O4?H7′–N2′ of the hydrogen-bonded 3AP dimer complex are stronger in the electronically excited state than in the ground state. Moreover, it has been demonstrated that the excited-state proton transfer reaction is facilitated by the electronic excited-state hydrogen bond strengthening.  相似文献   

13.
The syntheses of [Au(CC-4-C6H4CC-4-C6H4NN-4-C6H4NO2)(PPh3)] (3), trans-[Ru(CC-4-C6H4-CC-4-C6H4NN-4-C6H4NO2)Cl(dppm)2] (4), [Ru(CC-4-C6H4CC-4-C6H4NN-4-C6H4NO2)(dppe)(η-C5Me5)] (5), and [Ni(CC-4-C6H4NN-4-C6H4NO2)(PPh3)(η-C5H5)] (6) are reported, together with a single-crystal X-ray diffraction study of 4. Quadratic nonlinearities for 36 and [Ru(CC-4-C6H4NO2)(dppe)(η-C5Me5)] (7) have been determined at 1.064 μm and 1.300 μm by the hyper-Rayleigh scattering (HRS) technique, comparison to related complexes revealing that β values increase on introduction of azo group and π-system lengthening.  相似文献   

14.
The mixed ruthenium(II) complexes trans-[RuCl2(PPh3)2(bipy)] (1), trans-[RuCl2(PPh3)2(Me2bipy)](2), cis-[RuCl2(dcype)(bipy)](3), cis-[RuCl2(dcype)(Me2bipy)](4) (PPh3 = triphenylphosphine, dcype = 1,2-bis(dicyclohexylphosphino)ethane, bipy = 2,2′-bipyridine, Me2bipy = 4,4′-dimethyl-2,2′-bipyridine) were used as precursors to synthesize the associated vinylidene complexes. The complexes [RuCl(CCHPh)(PPh3)2(bipy)]PF6 (5), [RuCl(CCHPh)(PPh3)2(Me2bipy)]PF6 (6), [RuCl(CCHPh)(dcype)(bipy)]PF6 (7), [RuCl(CCHPh)(dcype)(bipy)]PF6 (8) were characterized and their spectral, electrochemical, photochemical and photophysical properties were examined. The emission assigned to the π–π1 excited state from the vinylidene ligand is irradiation wavelength (340, 400, 430 nm) and solvent (CH2Cl2, CH3CN, EtOH/MeOH) dependent. The cyclic voltammograms of (6) and (7) show a reversible metal oxidation peak and two successive ligand reductions in the +1.5-(−0.64) V range. The reduction of the vinylidene leads to the formation of the acetylide complex, but due the hydrogen abstraction the process is irreversible. The studies described here suggest that for practical applications such as functional materials, nonlinear optics, building blocks and supramolecular photochemistry.  相似文献   

15.
The broken-symmetry (BS) and multideterminant approaches to atomic oxygen (O), molecular oxygen (O2) and iron–oxo (Fe(IV)O) core in P450 have elucidated electronic structures of the ground triplet and excited singlet states, which indicate isoelectronic characteristics of the species. The dissociation processes of the O–O and Fe–O double bonds are also examined to clarify the radical character, namely O-atom property responsible for radical mechanism of hydroxylations of alkanes and epoxidation of alkenes. This isolobal analogy has indeed enabled us to propose possible reaction mechanisms of oxygenation reactions by the Fe(IV)O species on the basis of available theoretical and experimental results for O and O2. Similarly, an isolobal analogy of the σ* bond among Fe(IV)O, dioxirane, peracids, etc. indicates the common electrophilic property for the oxygenation reactions. The small energy gaps between the high- and low-spin states of the transition structures and intermediates generated in the oxygenation reactions are found to be origins for spin crossover phenomena along the reaction pathways of these reactions.  相似文献   

16.
We report the synthesis, crystal structure and electrochemical behaviour of a complex in which the Ph group of the phosphaalkene PhC(H)PMes* (Mes*: 2,4,6-tri-tert-butylphenyl) is coordinated to a chromium tricarbonyl group. The EPR spectra resulting from electrochemical and chemical reductions are described and the experimental g and hyperfine tensors (31P)T, as determined from the EPR data, are compared with those predicted by DFT calculations for the radical anion (Cr(CO)3, PhC(H)PMes). The structural changes caused by the addition of an electron to the neutral complex are described, together with an estimation of the contribution of Cr(CO)3 to the stabilization of the radical anion.  相似文献   

17.
Electrogenerated chemiluminescence (ECL) reactions involving the perylene cation radical (PE+) and perylene anion radical (PE) in acetonitrile have been observed using a dual-electrolysis stopped-flow method. In this method, ECL emission from the systems composed of different kinds of ion radicals can be easily observed by mixing both the electrolyzed solutions directly. Therefore, the ECL spectra were observed systematically in the reactions of PE+ and PE with different ion radicals. Consequently, emission definitely from the singlet state of PE was observed in the reactions between PE+ and the 9,10-diphenylanthracene anion radical (DPA), PE and DPA+, and PE and the thianthrene cation radical (TH+). In contrast, emission at long wavelength was obtained in the reaction between PE+ and the pyrene anion radical (PY) as well as the reaction between PE+ and PE. From this result, for the molecular interactions involving PE and PY, the presence of the π complexing interaction to form the π-excimer and the π-exciplex was strongly suggested in the ECL-emitting reactions. The present approach was thus found to be effective to reveal the molecular aspects of the excited states formed in solution.  相似文献   

18.
The calculations using the density functional theory (DFT) method were done on two diamagnetic oxo-bridged dinuclear rhenium complexes: [{Re(O)Br2(3,5-Me2pzH)2}2(μ-O)] (1) with a linear ORe–O–ReO core and [{Re(O)Br(3,5-Me2pzH)}2(μ-O)(μ-3,5-Me2pz)2] (2) with a bent Re2O3 unit (pzHmonodentate N-pyrazole and pzbidentate N,N′-pyrazole ligand). The optimized geometries of 1 and 2 agree with the X-ray structures. The MO sequence is almost the same for 1 with a linear ORe–O–ReO core and 2 with a bent Re2O3 unit. The bending of Re2O3 unit in 2 is a consequence of steric congestion introduced by two coordinated 3,5-dimethylopyrazole bridging ligands. Additional information about binding in the complexes 1 and 2 was obtained by NBO analysis.  相似文献   

19.
Two-dimensional (2D) correlation infrared (IR) spectroscopy has been applied to explore the effect of hydrogen bondings (HBs) on the structure of mesophase in the dissymmetrical 4-nitrobenzohydrazide derivative, N-(4-cetyloxybenzoyl)-N′-(4′-nitrobenzoyl) hydrazine (C16-NO2). The strength and species of HBs as well as the heat-induced structural variations in mesophase have been investigated. It has been found from 2D correlation IR spectroscopy that the sequential order of changes in the different functionalities in the course of liquid crystalline formation is that, firstly, the alkyl chain changes from the significant population of the trans conformation to the significant population of gauche conformation; then, the intermolecular HB between CO and NH groups is weakened, some even being broken, and consequently, the intermolecular distance is enlarged; finally, the skeleton of phenyl ring has enough space to change their conformation to weaken the π–π stacking interaction. In addition, besides a few free and some medium bonded NH and CO groups, strongly bonded NH and CO groups still predominantly exist in the mesophase.  相似文献   

20.
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   

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