Bonding in Elongated Dihydrogen Complexes. Theoretical Analysis of the Electron Density in [MLn(H···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)(NH 2 (CH 2 ) 2 NH 2 ) 2 (RCO 2 )] +, and OsH 4 (PR 3 ) 3 ) spanning a large range of H−H values is optimized at the B3LYP computational level, yielding satisfactory agreement with available neutron-diffraction data. The electron density resulting from these theoretical calculations is analyzed afterward within the “atoms in molecules” formalism, resulting in a positive 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)(NH 2 (CH 2 ) 2 NH 2 ) 2 (RCO 2 )] + and OsH 4 (PR 3 ) 3 as dihydride complexes.