A computational study on mixed-ligand N2P3 donor-set iron(II) and ruthenium(II) classical and non-classical hydrides

Iron and ruthenium classical and non-classical hydrides of the type [MH(N–N)P3]+ and [M(η2-H2)(N–N)P3]2+ {M = Fe, Ru; N–N = 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen); P = phosphites} were reported in 2004 together with an evaluation of the pseudo-aqueous pKa values of the η2-H2 complexes. The non-classical hydrides, even if doubly charged, showed a relatively low acidity, their pKa values ranging between −5.4 and −4.3. Moreover, ruthenium(II) derivatives showed to be more acidic than the corresponding iron(II) complexes. Information about the structural and electronic proprieties of complexes of this type, which allowed to better understand the role of both the metal centres and the ancillary ligands in the acidity of the co-ordinated hydrogen molecule, was obtained on the basis of DFT B3LYP calculations.

The results of DFT calculations on hydride complexes of the type [MH(N–N)P3]+ and [M(η2-H2)(N–N)P3]2+ {M = Fe, Ru; N–N = 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen); P = PH3, PF3}, are described. A good correlation between various computed molecular properties and experimental data reported in the literature is highlighted. The charge distributions obtained from DFT calculations allow to hypothesize that the different acidities of iron and ruthenium non-classical hydrides could be mainly justified on the basis of the difference of electronegativity of the two metal ions considered.Figure optionsDownload as PowerPoint slide