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Abstract: A theoretical investigation at DFT (B3LYP) level on the cyclopropanation reactions catalyzed by nickel(0) and nickel(II) have been extensively investigated. The computation results show that the active catalytic species formed by a CH2 fragment and the Cl2Ni(PH3)2 is carbenoids (PH3)2Ni(CH2Cl)Cl (IMA) and (PH3)Ni(CH2PH3)Cl2 (IMB), but both the carbenes (Cl2NiCH2 (IMC), (PH3)3NiCH2 (IME) and (PH3)2NiCH2 (IMG)) and carbenoids (ClNiCH2Cl (IMD), Ni(CH2PH3)(PH3)2 (IMF) and Ni(CH2PH3)PH3 (IMH)) are active catalytic species obtained from NiCl2, Ni(PH3)3, Ni(PH3)2 and a CH2 fragment. The cyclopropanation reaction proceeds through either concerted or multistep reaction pathway. The most favor cyclopropanation reactions catalyzed by nickel(II) is multistep pathway for IMD with a barrier of 21.65kcalmol−1 but is endothermic 6.74kcalmol−1, and the most favor nickel(0) catalyzed cyclopropanation reactions is also multistep pathway for IME, IMH and IMG species all with barriers of 21.93kcalmol−1 but the downhill potential energy surface discloses that each step of the cyclopropanation reaction are all irreversible. Thus, nickel(0) catalyzed cyclopropanation reaction proceed easer than nickel(II). [Copyright &y& Elsevier]

Abstract: The mechanism for the ion–molecule reaction of benzene anion with nitrous oxide has been characterized using the second-order Møller–Plesset perturbation theory (MP2). All the stationary points were determined at the MP2/6-31++G(d,p) level of the theory. As a result, our theoretical investigations strongly suggest that the main pathways on the potential energy surface can be pathways 1 and 2 of the Channel 1 which are two reciprocally competitive pathways, the minor ones can be expressed as pathway (Channel 1) 3 and Channel 2, and Channel 3 should be a competitive reactive pathway relative to the main reactive pathways. Theoretical calculated results are basically consistent with the experimental postulate. Furthermore, some specific character of the reaction of with N2O has been educed by the mechanism study. [Copyright &y& Elsevier]

Abstract: The gas-phase reactions of fluorocarbon compounds CH4– n F n (n =1–3) with Pt (3D, 1S) have been systematically explored via density functional theory (DFT) in order to investigate the mechanisms of these reactions. The results indicate that a reaction of CH3F with Pt (3D, 1S) experiences a rearrangement process to generate counterintuitive production (CH2F−PtH). CH2F2 and CHF3 activation by Pt (3D, 1S) yields high-oxidation-state complexes with carbon–metal double bonds. Moreover, the attack of platinum atoms on fluorine atoms in different fluorocarbon compounds involves intersystem crossing (ISC) between triplet and singlet state Potential Energy Surfaces (PESs). The crossing points (CPs) have been located by the intrinsic reaction coordinate (IRC) approach used by Yoshizawa et al. and corresponding minimum energy crossing points (MECPs) obtained by the mathematical algorithm proposed by Harvey et al. have also been used. Additionally, possible spin inversion processes are discussed using spin–orbit coupling (SOC) calculations. [ABSTRACT FROM AUTHOR]

Abstract: Calculations based on density functional theory (DFT) have been carried out to investigate geometries and bonding characteristics of all the stationary points associated with the gas-phase ion/molecule reactions of YNH+ (1∑+) with propene. The potential energy surface (PES), including six reaction pathways (four dehydrogenation and two demethanation processes), has been explored and analyzed. By contrast, dehydrogenation reaction channels that are associated with two consecutive hydrogen transfers from C atoms of propene fragment to Y atom of YNH+ moiety and then elimination of H2, are energetically favorable, which is in good agreement with the experimental observation. [Copyright &y& Elsevier]

Abstract: The reaction of La+ with CH3F, which was selected as a representative system of the activation of C–F bond in fluorohydrocarbons by bare lanthanide cations, has been examined using density functional theory (DFT) to explore more integrated reaction pathways and mechanisms on both singlet and triplet potential energy surfaces (PESs). A direct fluorine abstraction mechanism and an insertion–elimination mechanism were revealed, the related thermochemistry data involved in reaction of La++CH3F were determined. The crossing points (CPs) have been found by means of single-point computations as a function of the structural change along the intrinsic reaction coordinate (IRC) in this manuscript. The present results not only support the existing reaction conclusions inferred from early experimental data, but also complement the pathway and mechanism for this reaction, which can act as a guide for further experimental researches and theoretical investigations. [Copyright &y& Elsevier]

Abstract: The reactivity of X(3P) (X=Ge, Sn, Pb) with N2O(X1Σ) on both singlet and triplet potential energy surfaces have been investigated at the B3LYP level of theory. To accurately evaluate the activation barrier and reaction energy, the coupled cluster single point calculations using the B3LYP structures is performed. The calculated results are in good agreement with experimental observations. The (X=Ge, Sn, and Pb) reactions that Arthur Fontijn has been observed are spin-forbidden for formation of ground state products in the experiments. The present paper is discussed with the aid of the direct abstraction (DA) mechanism (also called the surface crossing model), a correlation argument based on separated fragments X+O+N2 can explain the inefficiency of the (X=Ge, Sn, and Pb) reactions at 298K by the need to switch electron configurations along low-energy adiabatic paths from ground-state reactants to energetically accessible product states. [Copyright &y& Elsevier]