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A recent study of the oxidative addition of zerovalent Ni to the C–CN bond of F-substituted benzonitriles showed significantly increased stabilization of the C–CN oxidative addition products with o-F groups (−6.6 kcal/mol per o-F) compared to m-F groups (−1.8 kcal/mol per m-F). To answer the question of whether this is an o-F effect or an orthoeffect, in this study the effect of CF3and CH3groups on the oxidative addition of the [Ni(dmpe)] fragment [dmpe = 1,2-bis(dimethylphosphino)ethane] to the C–CN bond of benzonitriles has been studied. A density functional theory study of the reaction pathway between η2-CN complexes and the C–CN oxidative addition products shows stabilization of the C–CN oxidative addition product with the electron-withdrawing CF3group and destabilization with the electron-donating CH3group in both tetrahydrofuran and toluene. There is a slightly larger orthoeffect with CF3(−7.4 kcal/mol) than with F. However, due to steric crowding, two o-CF3groups did not show considerably more stabilization than one o-CF3group. There is a linear relationship between ΔG°and the number of metagroups (2.0 kcal/mol stabilization per m-CF3and 0.8 kcal/mol destabilization per m-CH3). On the basis of natural population analysis, as the C–CN bond becomes more polarized, the stability of the C–CN oxidative addition products with respect to the η2-CN complexes increases.

A thermal reaction of amines, anilines, and amides with Tp′Rh(PMe3)(CH3)H (1, Tp′ = tris(3,5-dimethyl-pyrazolyl)borate) is described in this report. No N–H bond cleavage was observed for reactions between ammonia or unsubstituted aliphatic amines with the reactive fragment [Tp′Rh(PMe3)]. Instead, amine coordination products (κ2-Tp′)Rh(PMe3)(NHR1R2) (R1= H, R2= H, nPr, iPr, octyl; R1= R2= Et; R1, R2: pyrrolidine) were observed, and the crystal structure of (κ2-Tp′)Rh(PMe3)(NH2iPr) is reported. No coordination products were observed when 1was reacted with 1,1,1,3,3,3-hexafluoropropan-2-amine, anilines, and amides. Instead, the oxidative addition products (κ3-Tp′)Rh(PMe3)(NHR)H (R = CH(CF3)2, C6H5, 3,5-dimethylbenzyl, C6F5, C(O)CH3, C(O)CF3) were observed. Both RhI–N coordination products (κ2-Tp′)Rh(PMe3)(NH2CH2CF3) and RhIIIN–H addition products (κ3-Tp′)Rh(PMe3)(NHCH2CF3)H were generated when 1was reacted with 2,2,2-trifluoroethylamine. Coordination products dissociate ammonia and amines in benzene much faster than oxidative addition products eliminate anilines and amides. The relative metal–nitrogen bond energies were studied using established kinetic techniques. Analysis of the relationship between the relative M–N bond strengths and N–H bond strengths showed a linear correlation with a slope = RM–N/N–Hof 0.91 (10), indicating that the Rh–N bond strength varies in direct proportion to the N–H bond strength.