Effect of substituents in governing the homolytic gas-phase P–H bond dissociation enthalpies of phosphine-type oxides (R¹R²P(=O)H)

This study reports the gas-phase homolytic P–H BDEs of a set of 30 phosphine-type oxides (i.e., R¹R²P(=O)H) obtained using the W1w thermochemical protocol. We note that the P–H BDEs (at 298 K) of the species in this dataset differ by as much as 157.2 kJ mol^–1, with (H₂B)₂P(=O)H having the lowest BDE (249.3 kJ mol^–1) and F₂P(=O)H having the highest (406.5 kJ mol^–1). Furthermore, using the full set of 30 all-electron, non-relativistic, vibrationless bottom-of-the-well W1w P–H BDEs as reference values, we have identified several well-performing DFT methods that could be applied to the computation of the P–H BDEs of phosphine-type oxides. The best-performing DFTs (in conjunction with the A'VTZ basis set) were shown to be MN12-SX (MAD = 1.7 kJ mol^–1) and MN12-L (MAD = 2.7 kJ mol^–1).