Abstract:
The ruthenium complex with (N,N,N-tris
(benzimidazol-2yl-methyl)amine, L1
) was prepared, and characterized.
Fukui data were used to localize the reactive sites on
the ligand. The structural and electronic properties of the complex
were analyzed by DFT in different oxidation states in
order to evaluate its oxidant properties for phenol oxidation.
The results show that the hard Ru(IV) cation bonds preferentially
with a hard base (Namine = amine nitrogen, or axial chloride
ion), and soft Ru(II) with a soft base (Nbzim = benzimidazole
nitrogen or axial triphenyl phosphine). Furthermore, the
Jahn-Teller effect causes an elongation of the axial bond in the
octahedral structure. The bonding nature and the orbital contribution
to the electronic transitions of the complex were
studied. The experimental UV-visible bands were interpreted
by using TD-DFT studies. The complex oxidizes phenol to
benzoquinone in the presence of H2O2 and the intermediate
was detected by HPLC and 13C NMR. A possible mechanism
and rate law are proposed for the oxidation. The adduct formation
of phenol with [Ru(O)L1
]
2+ or [Ru(OH)L1
]
+ is theoretically
analyzed to show that [Ru(OH)L1
-OPh]+ could produce
the phenol radical.
