Electron transfers? assessment between stannol ring of triple-decker complexes and M(CO)5 (M = Cr, Mo, W), MnCp(CO)2 and CoCp(CO) metallic fragments: Bonding and energy decomposition analysis

Density functional theory (DFT) calculations using BP86 and B3LYP* functionals have been performed on a series of triple-decker complexes [(M'Cp)(2)(C4Sn)](R) (M' = Fe, Ru and R = Cr(CO)(5), Mo(CO)(5), W(CO)(5), MnCp(CO)(2) and CoCp(CO)) of 30-MVE (metal valence electrons) count to investigate the electronic structure, the bonding and the energy decomposition. The bonding is evaluated through the interactions between Sn(II) and R metallic fragments. The optimized structures for the considered complexes are comparable to the available X-ray data. The bonding energies have been calculated for all considered systems and their dependence on the nature of the metal cation of the R metallic fragment and its environment has been discussed. The increase of the MVE of the R fragments conducts to a remarkable increase of Sn-metal interactions. The natural charges and the localization of the molecular orbitals have been used to predict the variation of the interactions with the nature of the metal fragment. The sigma-donation (L -> M) and pi-backdonation (L -> M) (L = (M'Cp)(2)(C4Sn) and M = the metal of the R metallic fragment) are evaluated based on the donor-acceptor electrons transfers showing the strength of the former and the cancellation or partial cancellation of the later. The electrostatic and orbital interaction contributions and the role of sigma donor and pi acceptor bonding are for a great significance in relationship with the energy decomposition analysis (EDA). The Sn-Metal bonding was revealed to be more ionic than covalent in relationship with the proportion of delta E(elstat )and delta E(orb )into the total of attractive interactions (delta E-elstat + delta E-orb) and it is well correlated to its bond distance and its Wiberg bond index. The pi bonding for Cr(CO)(5), Mo(CO)(5) and W(CO)5 is weak but not totally suppressed, contrarily to that for MnCp(CO)(2) and CoCp(CO) which contributes significantly by about 22% and 26%, into the total orbital interactions, respectively.