An experimental and theoretical approach to phosphonodithioato complexes: molecular orbital analysis by hybrid-DFT and EHT calculations on trans-bis[O-alkyl-phenylphosphonodithioato][Ni.sup.II], and vibrational assignments

The synthesis and the full spectroscopic characterization (FT-IR, FT- Raman, [sup.31]P CP MAS NMR) of trans-bis[O-ethyl-phenylphosphonodithioato][Ni.sup.II] (3) are reported. On the basis of hybrid-Density Functional Theory (DFT) calculations and Extended Huckel Theory (EHT) calculations, performed on the simpler trans-bis[O-methyl-phenylphosphonodithioato][Ni.sup.II] (2) model complex, the electronic structures of phosphonodithioato complexes in their ground states are fully described, and in particular the vibrational features are deeply analyzed, allowing an unprecedented insight into the vibrational features of trans-bis-O-methyl-phenylphosphono- and trans-bis(isopropylamidophosphono)-dithioato complexes of nickel(II), palladium(II), and platinum(II). Key words: phosphonodithioato complexes, IR, Raman, DFT calculation.