with a development version of the GPU-accelerated electronic structure code TeraChem v1.9. We chose the range-separated hybrid functional ωPBEh (default ω = 0.2 bohr -1 ) to avoid the unphysical HOMO-LUMO gap closing that occurs in larger systems with global hybrid functionals. The LACVP* composite basis set was employed throughout our work, which consists of a LANL2DZ effective core potential for metals and the 6-31G* basis for all other atoms. We confirmed that reaction energetics are not strongly sensitive to our omission of semiempirical dispersion, choice of functional (i.e., B3LYP global hybrid versus range-separated hybrid wPBEh), and basis set size (i.e., def2-TZVP vs LACVP*, Supporting Information Figure ). We carried out closed-shell singlet calculations in a spin-restricted formalism and all other calculations in a spin-unrestricted formalism that employed level shifting 89 of 0.25 Ha for both majority-and minority-spin virtual orbitals to enable the convergence of the self-consistent field (SCF). We used the default SCF convergence threshold of 3x10 -5 hartree for the direct inversion of the iterative subspace (DIIS) error. We carried out geometry optimizations in the translationrotation-internal coordinate (TRIC) optimizer, with default tolerances for the maximum gradient of 4.5×10 -4 hartree/bohr and the energy difference between steps of 1×10 -6 hartree.