Toward the Rational Design of an OsM4 Center for Methane Activation: Gas-Phase Result-Derived Neural Network Model.

Gas-phase reactions of [OsB_x]⁺ (x = 1-4) with methane at ambient temperature have been studied by using quadrupole-ion trap mass spectrometry combined with quantum chemical calculations. The [OsB_x]⁺ (x = 1-4) cluster ions can undergo dehydrogenation reactions with methane. Comprehensive analysis of the [OsB_x]⁺/CH₄ (x = 1-4) system with Os-complexes ([OsC_y]⁺ (y = 1-3) and [OsO_z]⁺ (z = 1-3)) shows that the large polarity of the cluster and the high sum of the pair energies between Os and the ligand in the ETS-NOCV combine to promote the ability of the cluster to activate methane. Cluster polarity may induce heterolytic cleavage of the C-H bond, and the sum of the pair energies of the fragments may reduce the cluster orbital energy to match the methane orbital and improve the cluster stability. The synergistic interplay of these two factors may offer a viable approach for the activation of methane in the condensed phase, which involves modulating the coordination environment of the active sites to enhance the stability and facilitate C-H bond cleavage and the degree of matching with methane orbitals. A nonlinear function is used to extract second-order characteristic features that have a significant impact on the energy difference based on the limited energy difference data of the OsB_mC_nO_lH_k units. A neural network model is next designed to predict the reaction barrier for methane conversion by OsM₄⁺ (M = C, N, O, Al, Si, or P) with high accuracy.