静磁场中的互作用能

讨论了在激发磁场的电流保持不变时和束缚磁荷作为磁场的不变时，两种情况下磁场的相互作用能。结果与静电场类似，两种情况的互作用能中都含有相互磁化，致使物体磁化状态改变作的功。     

Transition state geometry in radical abstraction reactions: comparison of interatomic distances in the intersecting parabolas and Morse curves models with quantum-chemical calculations

Interatomic distances in the transition state were estimated for the reactions of radical abstraction: H^· + H₂, H^· + HCl, H^· + CH₄, N^·H₂ + NH₃, HO^· + H₂O, HO₂ ^· + HOOH, and C^·H₃ + SiH₄. The calculation was performed by the quantum-chemical density functional method or coupled clusters method (QCH), as well as by the methods of intersecting parabolas (IPM) and Morse curves (IMM), using experimental data (activation energies and reaction enthalpies). The results of the latter two methods are close to the quantum-chemical calculation and differ only by the increment a: r(IPM or IMM) = a + r(QCH), where a = –4.5·10^–12 m for IPM and a = +1.9·10^–12 m for IMM.     

Kinetics of the Reaction of Abstracting Hydrogen from Ethylene by Hydrogen Atom

Hydrogen abstraction reaction, H C2H4 --H2 C2H2 was studied by using A initio SCF method. Ge-ometries were fully optimized at SCF level and energies were computed at STO-3G basis set for reactants and transition state. Vibrational analysis was performed thereupon. Finally, the rate constant calculations were carried out at different temperatures for all range of reaction temperature according to Eyring's sbwlute reaction rate theory. The calculated activation energy is 12. 68 kcal/mol, lower than observed value (H. S kcal/mol) by 1. 82 kcal/mol only. The agreement of the calculated rate constants with the experiments is satisfactory.     

Oxidative Reactions of the MoIV Dialkyl Complex [{(3‐CF3C6H4NCH2CH2)2NMe}Mo(CH2SiMe3)2]

The structure of [(CF₃N₂NMe)Mo(CH₂SiMe₃)₂] (in which (CF₃N₂NMe)^2? is [(3‐CF₃C₆H₄NCH₂CH₂)₂NMe]^2?) is approximately trigonal bipyramidal with one axial and one equatorial alkyl ligand. Heating of solutions of [(CF₃N₂NMe)Mo(CH₂SiMe₃)₂] in [D₆]benzene in the presence of five equivalents of 2‐butyne led to diamagnetic [(CF₃N₂NMe)Mo(CHSiMe₃)(η²‐MeC?CMe)], whose structure is approximately square pyramidal with the alkyne occupying the axial site. Addition of one equivalent of cyclohexene sulfide to [(CF₃N₂NMe)Mo(CH₂SiMe₃)₂] at room temperature produced the diamagnetic, dimeric molybdenum(IV) sulfido complex, [{(CF₃N₂NMe)MoS}₂]. This complex is composed of two approximately trigonal bipyramidal centers, each containing one axial and one equatorial sulfur atom. Oxidation of [(CF₃N₂NMe)Mo(CH₂SiMe₃)₂] with hexachloroethane resulted in formation of tetramethylsilane, HCl, and the sparingly soluble, red alkylidyne complex, [{(CF₃N₂NMe)Mo(CSiMe₃)Cl}₂]. This complex forms a dimer through bridging chlorides. The oxidation reactions of [(CF₃N₂NMe)Mo(CH₂SiMe₃)₂] with 2‐butyne, cyclohexene sulfide, or C₂Cl₆ are all proposed to proceed by α‐hydrogen abstraction in the Mo^VI species to yield (initially) the Mo?CHSiMe₃ species and tetramethylsilane.     

Tricarbonyl(N,N-Disubstituted-Cyclohexadienecarboxamide)iron Complexes: Investigation of the Possible Intramolecular Interaction between the Iron Center and the Amide Substituent

Direct reaction of iron pentacarbonyl with 1-N,N-disubstituted-cyclohexa-2,5-dicnecarboxamide and 1-N,N-disubstituted-cyclohexa-1,3-dienecarboxamide mixture (in which the disubstkuted group is diethyl or diphenyl) gave the isomeric tricarbonyl iron complexes of 2-N,N-disubstituted-1,4-η-cyclohexa-1,3-dienccarboxamide (1), 1-N,N-disubslituted-1,4-η-cyclohexa-1,3-dienecarboxamide (2), and 5-N,N-disubstituted-1,4-η-cyclohexa-1,3-dienecarboxamide (3) and tricarbonyliron complexes of l-N,N-disubstituted-cyclohexenecarboxamide (4). These complexes were separated and characterized by IR, UV-VIS, ¹H NMR, elemental analysis, and mass spectra. Only 1 isomerized to give 2 under acidic conditions; both 1 and 2 undergo hydride abstraction with triphenylmethyl hexafluorophosphatc. Complexes 3, undergo neither isomcrization nor hydride abstraction. According to the spectral data, the possible interaction between carboxamide and iron carbonyl moiety was investigated. The irreversible electrochemical behavior of these complexes were studied.     

Methyl abstraction kinetics of CpFe(CO)2Me using the benzyl radical clock

The rate constant for the methyl abstraction reaction of CpFe(CO)₂Me has been measured with the benzyl radical clock as (1.1 ± 0.2) × 10⁵ M⁻¹ s⁻¹ at room temperature. Time-resolved Fourier-transform Infrared (FTIR) absorption spectroscopy pointed towards the formation of the CpFe(CO)₂ radical upon benzyl abstraction. The main stable product has been established by a linear scan of the reaction mixture as Cp₂Fe₂(CO)₄ produced by the dimerization of the CpFe(CO)₂ radicals. The transition state structure for the abstraction process was also found at UB3LYP/6-311+G* level of theory to contain a planar CH₃ group.     

Origin of the Correlation of the Rate Constant of Substrate Hydroxylation by Nonheme Iron(IV)–oxo Complexes with the Bond‐Dissociation Energy of the C?H Bond of the Substrate

A series of hydrogen‐abstraction barriers of a nonheme iron(IV)–oxo oxidant mimicking the active species of taurine/α‐ketoglutarate dioxygenase (TauD) are rationalized by using a valence‐bond curve‐crossing diagram (see figure). It is shown that the barriers correlate with the strength of the C? H bond. Furthermore, electronic differences explain the differences between nonheme and heme iron(IV)–oxo hydrogen‐abstraction barriers.

     

Hydridoorganostannylene Coordination: Group 4 Metallocene Dichloride Reduction in Reaction with Organodihydridostannate Anions

Organodihydridoelement anions of germanium and tin were reacted with metallocene dichlorides of Group 4 metals Ti, Zr and Hf. The germate anion [Ar*GeH₂]⁻ reacts with hafnocene dichloride under formation of the substitution product [Cp₂Hf(GeH₂Ar*)₂]. Reaction of the organodihydridostannate with metallocene dichlorides affords the reduction products [Cp₂M(SnHAr*)₂] (M=Ti, Zr, Hf). Abstraction of a hydride substituent from the titanium bis(hydridoorganostannylene) complex results in formation of cation [Cp₂M(SnAr*)(SnHAr*)]⁺ exhibiting a short Ti–Sn interaction. (Ar*=2,6-Trip₂C₆H₃, Trip=2,4,6-triisopropylphenyl).     

Gas-Phase Synthesis of Triphenylene (C18H12)

For the last decades, the hydrogen-abstraction−acetylene-addition (HACA) mechanism has been widely invoked to rationalize the high-temperature synthesis of PAHs as detected in carbonaceous meteorites (CM) and proposed to exist in the interstellar medium (ISM). By unravelling the chemistry of the 9-phenanthrenyl radical ([C₁₄H₉]^.) with vinylacetylene (C₄H₄), we present the first compelling evidence of a barrier-less pathway leading to a prototype tetracyclic PAH – triphenylene (C₁₈H₁₂) – via an unconventional hydrogen abstraction–vinylacetylene addition (HAVA) mechanism operational at temperatures as low as 10 K. The barrier-less, exoergic nature of the reaction reveals HAVA as a versatile reaction mechanism that may drive molecular mass growth processes to PAHs and even two-dimensional, graphene-type nanostructures in cold environments in deep space thus leading to a better understanding of the carbon chemistry in our universe through the untangling of elementary reactions on the most fundamental level.