In this work, we establish quantitative structure–property relationships (QSPR) to predict the melting temperatures of diphosphine dioxides possessing a tetradecahydrophosphanthrene core, based on four two-parameter models. Three new compounds were synthesized using the Bouveault–Blanc reduction of appropriate tertiary phosphine oxides, and these compounds exhibit high melting temperatures (approximately 280–410 °C). Models were built using a dataset of 13 compounds, including the new ones. It was found that models 1 and 2, based on molecular volume, yield satisfactory results for the entire dataset, whereas models 3 and 4, based on the calculated lattice energy from crystal structures, provide even better predictions for all compounds. The new compounds were characterized by X-ray structural analysis, differential scanning calorimetry, and theoretical calculations. Cluster analysis indicates that, for crystal stability, van der Waals forces are as important as Coulombic interactions in stabilizing the crystal lattice. Graphical abstract: Rationalization of the thermal properties of some polycyclic organophosphorus compounds by structural and QSPR analyses