Iron-Catalyzed Oxidation of 1-Phenylethanol and Glycerol With Hydrogen Peroxide in Water Medium: Effect of the Nitrogen Ligand on Catalytic Activity and Selectivity.

The iron(II) complexes [Fe(bpy)3](OTf)2 (bpy = 2,2'-bipyridine; OTf = CF3SO3) (1) and [Fe(bpydeg)3](OTf)2 (bpydeg = N 4,N 4-bis(2-(2-methoxyethoxy)ethyl) [2,2'-bipyridine]-4,4'-dicarboxamide) (2), the latter being a newly synthesized ligand, were employed as catalyst precursors for the oxidation of 1-phenylethanol with hydrogen peroxide in water, using either microwave or conventional heating. With the same oxidant and medium the oxidation of glycerol was also explored in the presence of 1 and 2, as well as of two similar iron(II) complexes bearing tridentate ligands, i.e., [Fe(terpy)2](OTf)2 (terpy = 2, 6-di(2-pyridyl)pyridine) (3) and [Fe(bpa)2](OTf)2 (bpa = bis(2-pyridinylmethyl)amine) (4): in most reactions the major product formed was formic acid, although with careful tuning of the experimental conditions significant amounts of dihydroxyacetone were obtained. Addition of heterocyclic amino acids (e.g., picolinic acid) increased the reaction yields of most catalytic reactions. The effect of such additives on the evolution of the catalyst precursors was studied by spectroscopic (NMR, UV-visible) and ESI-MS techniques.

Evaluation of the donor ability of phenanthrolines in iridium complexes by means of synchrotron radiation photoemission spectroscopy and DFT calculations.

Synchrotron radiation XPS measurements of Ir 4f, N 1s and I 4d core levels for the compounds Ir(cod)(N-N)X (cod=1,5-cyclooctadiene; N-N=1,10-phenanthroline and substituted derivatives; X=Cl, I) are reported. The compounds Ir(cod)(3,4,7,8-Me4phen)X (3,4,7,8-Me4phen=3,4,7,8-tetramethyl-1,10-phenanthroline) were structurally characterized by single crystal X-ray analyses. The comparison among the binding energies shows differences that are interpreted in terms of electron density variations due to the change of the phenanthroline substituents. Such analysis provides a quantitative evaluation of the ligand donor properties. The trend in the measured binding energies is confirmed by the results obtained by DFT DeltaSCF calculations, which include final state relaxation effects, while the specific role of initial state effects has been assessed in terms of the Kohn-Sham eigenvalues analysis.