Abstract
We report a reparameterization of PM6 parameters for fluorine and chlorine using our training set containing transition metal complexes. Spin unrestricted calculations with the resulting rPM6 (UrPM6) were examined quantitatively using two test sets: (i) the description of magnetic interactions in 25 dinuclear metal complexes and (ii) the prediction of barrier heights and reaction energies for epoxidation and fluorination reactions catalyzed by high-valent manganese-oxo species. The conventional UPM6 and UPM7 methods were also evaluated for comparison on the basis of either experimental or computational (the UB3LYP/SVP level) outcomes. The merits of UrPM6 are highlighted by both the test sets. As regards magnetic exchange coupling constants, the UrPM6 method had the smallest mean absolute errors from the experimental data (19 cm−1), followed by UPM7 (119 cm−1) and UPM6 (373 cm−1). For the epoxidation and fluorination reactions, all of the transition state searches were successful using UrPM6, while the success rates obtained by UPM6 and UPM7 were only 50%. The UrPM6-optimized stationary points also agreed well with the reference UB3LYP-optimized geometries. The accuracy for estimating reaction energies was also greatly remedied.
Highlights
In oxidation reactions, mononuclear metal-oxo species such as Fe(IV)=O and Mn(IV)=O are considered to be key intermediates that activate inert C–H and C=C bonds to generate alcohols and epoxides [1]
As a continuation of our recent work, we presented the reparameterization of the PM6 parameter sets for fluorine and chlorine, both of which can play an important role in catalytic reactions
To avoid the degradation of the reparameterization’s accuracy for general chemical problems, several subsets in the GMTKN30 database were adopted in our training set
Summary
Mononuclear metal-oxo species such as Fe(IV)=O and Mn(IV)=O are considered to be key intermediates that activate inert C–H and C=C bonds to generate alcohols and epoxides [1]. Chiral MnIII -salen complexes achieve enantioselective epoxidation of olefins, so-called the Jacobsen-Katsuki epoxidation (see Scheme 1a) [2,3] This type of epoxidation reaction is expected to start with the attack of a MnV =O on one of the carbon atoms of the C=C bond. Groves and co-workers developed a late-stage developed a late-stage process for the 18F fluorination into the benzylic position of a molecule [10] They revealed a Mn(salen) into complex with p–toluenesulfonate significantly outperforms that with. We proposed the rPM6 method [48,49,50,51,52], which is a reparameterization variant of PM6 [53], and tested the spin unrestricted PM6 (UrPM6) against organic diradicals and iron– and manganese–catalyzed C–H and C=C bond activation reactions. The other set was composed of the two oxidation reactions as already noted above (see Scheme 1)
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