In all cases there seem to be an offset of approximately 0.5 kcal/mol in the D e -values compared to the reference DF-CCSD(T)-F12b/cc-pVDZ-F12 calculations. Overall, decent agreement between most of the MP2 methods is seen, with DF-MP2/aug-cc-pVDZ deviating and being slightly worse. Accuracy-wise the DF-MP2-F12/cc-pVTZ-F12 calculations of the D e best resembles the DF-CCSD(T)-F12b/cc-pVDZ-F12 reference.