Both theoretical values of NMR <sup>13</sup>С chemical shifts and frontier orbital energies (DFT method) for syn-[(1-R-η<sup>3</sup>-C<sub>3</sub>H<sub>4</sub>)Pd(Me<sub>2</sub>C=O)<sub>2</sub>]<sup>+</sup> follow one- and two-parameter linear regressions which involve σ<sup>+</sup> and σ<sup>-</sup> constants, as well as Swain-Lupton parameters R<sup>+</sup>, R<sup>-</sup> and F