C−F Bond Activation by the 14-Electron M(X)(PH₃)₂ (M = Rh, Ir; X = CH₃, H, Cl) Complex. A Density Functional Study

Abstract

The oxidative addition of the F−CH3 bond to coordinatively unsaturated trans-M(X)(PH3)2 (M = Rh, Ir; X = CH3, H, Cl) was theoretically investigated by density functional theory. All of the stationary points were determined at the B3LYP/LANL2DZ level. A configuration mixing model based on the theory of Pross and Shaik has been used to develop an explanation for the barrier height as well as the reaction enthalpy. Our theoretical findings suggest that the singlet−triplet splitting (ΔE st = E triplet − E singlet) of the ML3 species can be used as a basis to predict its reaction activity for oxidative additions; i.e., the smaller the ΔE st of ML3, the lower the barrier height and the larger the exothermicity, in turn, the faster the oxidative addition reaction. Considering the substituent effect, and the nature of the central metal, the following conclusions therefore emerge: for the 14-electron trans-M(X)(PH3)2 complex, a stronger π-donor ligand (such as Cl) as well as a heavier transition metal center (the third-row) will result in a smaller ΔE st, and thus will provide a potential model for the oxidative addition of saturated C−F bonds. In this work, an energetically feasible reaction mechanism which should not have radical intermediates involved is suggested.

Ill‐defined chemical concepts: The problem of quantification

“…There has been (and still is) a long lasting controversy about the bond order of the gallium-gallium bond in Greg Robinson's trans-bent Na 2 [Mes* 2 C 6 H 3 2 GaGa 2 C 6 H 3 Mes* 2 ] (Mes* 5 2,4,6-i-Pr 3 C 6 H 2 ), published nearly 20 years ago. [36] The small GaAGa distance of 2.32 Ang measured by X-ray experiments (see Figure 6) and theoretical studies using different population analysis methods pointed to a triple bond, while the numerical values of the calculated bond order differed between 1.7 and 3.2.…”

“…Is there a gallium-gallium triple bond? The crystal structure of compound published by Su et al, which led to so many discussions in the literature[36] FIG URE 7 Computed (B3LYP/D3 def2tzvp) structures of a prototypical Gallane (1), Gallene (2), Gallyne (3; Nimag 5 2) and Greg Robinson's trans bent di-gallium compound(4)Compared with the carbon carbon (4.54 N/cm) or the carbon hydrogen bonds (5.55 N/cm) in (4) the Gallium backbone is extremely soft (0.84 and 1.15 N/cm for the GaAGa and the GaAC connectivity, respectively). To maximize the sodium-(p) sandwich attraction, and in turn to minimize the total energy, the weakest part of the system (the GaAGa bond) will be compressed, without paying too much penalty.This is exactly what a computed soft (relaxed) force constant predicts: it does not matter if the bond is stretched or compressed by secondary interactions by, let us say, 10%.…”

Synthesis and Structure of the “Dialuminyne” Na2[Ar′AlAlAr′] and Na2[(Ar′′Al)3]: AlAl Bonding in Al2Na2 and Al3Na2 Clusters

“…Compounds 3 and 4 were synthesized by reduction of solutions of Ar'AlI 2 (5) and Ar''AlI 2 (8) in diethyl ether with excess sodium [Eq. (1)].…”

Atmospheric Selective Oxidation of Benzyl Alcohol Catalyzed by Pd Nanoparticles Supported on CeO2 with Various Morphologies

“…97%, much higher than the value gained in the presence of toluene. The difference is probably owing to the fact that the fluorinated solvent is able to dissolve higher amount of oxygen, which is also reported by Su et al [28] Furthermore, it is of interest to discover that the selective oxidation reaction could also offer a moderate activity in the presence of H 2 O or ethanol. The inferior catalytic activity to the cases gained in the abovementioned organic solvents is mainly originated from the Table 1.…”