Dft Study On Pi Back-Donation Effects Of Aromatic And Alkyl Sulfoxide-Palladium(Ii) Complexes

Theoretical calculations on di-phenyl sulfoxide (DPSO) and di-n-hexyl sulfoxide (DHSO) Pd(II) complexes had been carried out by DFT method. d-pi* back-donation bond could be found in these sulfoxide Pd(II) complexes, and pi back-donation bond in DPSO-Pd (II) complex is stronger than that in DHSO-Pd(II) complex, indicating the substituent of sulfoxide ligand can influence Pd-sulfoxide d-pi* back-donation interaction significantly. By BHandH/6-31+G** (Pd, 3-21G*)//BHandH/6-31G* (Pd, 3-21G*) method, the calculated d-pi* back-binding orbital energy of etrans-PdCl2 (DPSO)(2) is -10.695 eV, which is slightly lower than that of trans-PdCl2 (DHSO)(2) (-10.320 eV). The pi back-donation effect on the Pd(II)-S bond lengths were further examined by calculations on model complexes [trans-PdCl2 (CO)DHSO], [trans-PdCl2 (NH3)DHSO], [trans-PdCl2 (CO)DPSO] and [trans-PdCl2(NH3)DPSO] which contains sigma-donor(NH3) or pi-acceptor(CO) ligands. The change of Pd-S bond lengths in DHSO-Pd(II) complexes is obviously less than that in DPSO-Pd(II) complexes after the ligand substitution, suggesting DPSO-Pd(II)) complex has a stronger pi back-donation interaction than DHSO-Pd(II) complex.