Table and 2 show relevant energy gaps and SOCCs. As explained in Section 3.1, the calculations of MECPs in these species were far from trivial. The triplet propylene adducts are nearly isoenergetic, differing by less than 1 kcal/mol. At the optimized triplet geometries, the singlet is 2.3 kcal/mol above the triplet state. The MECP heights relative to the triplet minima are very small, i.e., less than 1 kcal/mol. All SOCCs for the propylene adduct (the arithmetic mean is 12.03 cm -1 and 15.00 cm -1 for the triplet geometries and the MECP respectively) are smaller than for the ethylene adduct, indicative of less efficient ISC, which qualitatively agrees with the experimentally observed smaller yield of singlet products in propylene.