728042-52-2

Two anilinosalen and a mixed phenol-anilinosalen ligands involving sterically hindered anilines moieties were synthesized. Their nickel(II) complexes 1, 2, and 3 were prepared and characterized. They could be readily one-electron oxidized (E1/2=-0.30, -0.26 and 0.10 V vs. Fc +/Fc, respectively) into anilinyl radicals species [1]+, [2]+, and [3]+, respectively. The radical complexes are extremely stable and were isolated as single crystals. X-ray crystallographic structures reveal that the changes in bond length resulting from oxidation do not exceed 0.02 A within the ligand framework in the symmetrical [1] + and [2]+. No quinoid bond pattern was present. In contrast, larger structural rearrangements were evidenced for the unsymmetrical [3]+, with shortening of one Cortho-Cmeta bond. Radical species [1]+ and [2]+ exhibit a strong absorption band at around 6000 cm-1 (class III mixed valence compounds). This band is significantly less intense than [3]+, consistent with a rather localized anilinyl radical character, and thus a classification of this species as class II mixed-valence compound. Magnetic and electronic properties, as well as structural parameters, have been computed by DFT methods.

A series of new chiral N4-Schiff bases, containing amine or sulfonamide functionalities has been synthesized. Coupled with ruthenium catalysts, these Schiff bases induce interesting results in the hydrogenation of acetophenone: complete conversion and 76% ee were obtained with the catalytic system Ru(PPh3)3Cl2/(1R,2R)-N,N′-bis-(2- p-tosylaminobenzylidene)-1,2-diphenylethylenediamine. A very important phosphine co-ligand effect was observed on both activity and enantioselectivity of the catalysts. However, without the co-ligand, we obtained an enantioselectivity for the (R)-enantiomer, whereas with nonchiral co-ligand an enantioselectivity for the (S)-enantiomer was observed.