The organophosphorus compounds o-Ph2P(O)C6H4OCH3 and Ph2P(O)C2H4OCH3, which are analogs of podands' terminal groups, have been synthesized. The thermodynamic characteristics of their complexation with LiNCS and NaNCS in acetonitrile were obtained by calorimetry. Molecular mechanics calculations on M+ L complexes with different stoichiometries M+:L = 1:1, 1:2 and 1:4 (M+ = Li+, Na+) were performed, as well as on their solvates with a limited number of MeCN molecules. It has been shown that the experimental data could be explained by taking into account both the specific features of the complex structure and the solvent effects. The possibility of the application of additive schemes in the investigation of the complexation of polydentate molecules is discussed.