BONDING IN ELONGATED DIHYDROGEN COMPLEXES - THEORETICAL-ANALYSIS OF THE ELECTRON-DENSITY IN [ML(N)(H-CENTER-DOT-CENTER-DOT-CENTER-DOT-H)] SPECIES

The geometry of a series of four [ML(n) ''H-2''] complexes (W(H-2)(CO) (3)(PR(3))(2), IrH(H ... H)-Cl-2(PR(3))(2), [OS(H ... H)(NH2(CH2)(2)NH 2)(2)(RCO(2))](+), and OsH4(PR(3))(3)) spanning a large range of H-H v alues is optimized at the B3LYP computational level, yielding satisfac tory agreement with available neutron-diffraction data. The electron d ensity resulting from these theoretical calculations is analyzed after ward within the ''atoms in molecules'' formalism, resulting in a posit ive assignment of the complexes W(H-2)(CO)(3)(PR(3))(2) and IrH(H ... H)Cl-2(PR(3))(2) as dihydrogen complexes and of the complexes [Os(H .. . H)(NH2(CH2)(2)NH2)(2)(RCO(2))](+) and OsH4-(PR(3))(3) as dihydride c omplexes.