Calculations on the Kinetics, Thermodynamics, and Selectivity of Methyl Radical Addition to Olefins Coordinated to d8 and d0 Transition-Metal Fragments: Two Distinct and Opposite anti-Evans−Polanyi Effects with Potential Practical Implications

Density functional study of S(N) 2 substitution reactions for CH(3) Cl + CX(1) X(2•-) (X(1) X(2) = HH, HF, HCl, HBr, HI, FF, ClCl, BrBr, and II)

A systematic investigation on the S(N) 2 displacement reactions of nine carbene radical anions toward the substrate CH(3) Cl has been theoretically carried out using the popular density functional theory functional BHandHLYP level with different basis sets 6-31+G (d, p)/relativistic effective core potential (RECP), 6-311++G (d, p)/RECP, and aug-cc-pVTZ/RECP. The studied models are CX(1) X(2•-) + CH(3) Cl → X(2) X(1) CH(3) C(•) + Cl(-) , with CX(1) X(2•-) = CH(2) (•-) , CHF(•-) , CHCl(•-) , CHBr(•-) , CHI(•-) , CF(2) (•-) , CCl(2) (•-) , CBr(2) (•-) , and CI(2) (•-) . The main results are proposed as follows: (a) Based on natural bond orbital (NBO), proton affinity (PA), and ionization energy (IE) analysis, reactant CH(2) (•-) should be a strongest base among the anion-containing species (CX(1) X(2•-) ) and so more favorable nucleophile. (b) Regardless of frontside attacking pathway or backside one, the S(N) 2 reaction starts at an identical precomplex whose formation with no barrier. (c) The back-S(N) 2 pathway is much more preferred than the front-S(N) 2 one in terms of the energy gaps [ΔE cent≠(front)-ΔE cent≠(back)], steric demand, NBO population analysis. Thus, the back-S(N) 2 reaction was discussed in detail. On the one hand, based on the energy barriers (ΔE cent≠ and ΔE ovr≠) analysis, we have strongly affirmed that the stabilization of back attacking transition states (b-TSs) presents increase in the order: b-TS-CI(2) < b-TS-CBr(2) < b-TS-CCl(2) < b-TS-CHI < b-TS-CHBr < b-TS-CHCl < b-TS-CF(2) < b-TS-CHF < b-TS-CH(2) . On the other hand, depended on discussions of the correlations of ΔE ovr≠ with influence factors (PA, IE, bond order, and ΔE def≠), we have explored how and to what extent they affect the reactions. Moreover, we have predicted that the less size of substitution (α-atom) required for the gas-phase reaction with α-nucleophile is related to the α-effect and estimated that the reaction with the stronger PA nucleophile, holding the lighter substituted atom, corresponds to the greater exothermicity given out from reactants to products.

Radicals in transition metal catalyzed reactions? transition metal catalyzed radical reactions? a fruitful interplay anyway: part 1. Radical catalysis by group 4 to group 7 elements

This review summarizes the current status of radical-based transition metal catalyzed reactions in organic chemistry. The underlying features of radical generation from transition metal complexes and radical reactivity in the framework of transition metal catalysis are discussed. The available arsenal to detect radicals in transition metal catalyzed transformations is presented. Available strategies to combine radical intermediates with transition metal catalysis are outlined. In the main part the currently known synthetic methodology of transition metal catalyzed reactions proceeding via radical intermediates is discussed. This part covers catalytic radical reactions involving group 4 to group 7 elements.