ELONGATED DIHYDROGEN COMPLEXES - A COMBINED ELECTRONIC DFT PLUS NUCLEAR-DYNAMICS STUDY OF THE -DOT-CENTER-DOT-CENTER-DOT-H)(C5H5)(H2PCH2PH2)](+) COMPLEX

A study on a modeled version of the complex [Ru(H ... H)(C5Me5)(dppm)] (+) has been performed both at electronic structure level and includin g quantum treatment of nuclei. Density functional theory (DFT) electro nic structure calculations alone fail to reproduce the experimentally reported geometry of the elongated dihydrogen ligand of the complex, e ven though the rest of the complex is satisfactorily described. Quantu m nuclear motion calculations manage to correctly explain the geometri es found experimentally by means of neutron diffraction measurements. Isotopic effects are predicted for the hydrogen-hydrogen distance of t he elongated dihydrogen ligand depending on its isotopic composition. Moreover, the temperature dependence of the J(H,D) coupling constant i s also interpreted successfully on the grounds of varying population o f the vibrational excited states of the Ru-H-2 unit.