Effects of substituents in the cationic and anionic η3-allylpalladium complexes according to data from 13C NMR spectroscopy and quantum chemical calculations

A linear correlation of chemical shifts (δ) of signals in the 13C NMR spectra of the unsubstituted terminal carbon atom of the allyl ligand in [(1-R-η3-C3H4)Pd]NO3 (R = Me, CH2OMe, CO2Me, COMe, CHO) with the substituent constants σ+ and σs- in acetone solutions was found. A considerable deviation from linearity was observed for R = Ph. The 13C nuclear magnetic screening constants were calculated by the DFT method in the GIAO approximation for equilibrium geometries of the cations [(1-R-η3-C3H4)Pd(Me2C=0)2]+ and anions [(1-R-η3-C3H4)PdCl2]s-. In the latter case, the theoretical and experimental δ values are consistent. The influence of the substituent R on the geometric parameters and charges on atoms in the neutral, anionic, and cationic η3-allylpalladium complexes is discussed.