Application of Pd(II) Complexes with Pyridines as Catalysts for the Reduction of Aromatic Nitro Compounds by CO/H2O

Many efforts have been undertaken to minimize the cost of large-scale conversion of aromatic nitro compounds to amines Toward this end, application of CO/H2O as a reducing agent instead of molecular hydrogen seems to be a promising method, and the process can be catalyzed by Pd(II) complexes. In this work, the catalytic activity of square planar complexes of general structure PdCl2(XnPy)(2) (where XnPy = pyridine derivative) was studied. Particular attention was paid to the effects of substituents both in the aromatic ring of XnPy (ligand) and the nitro compound to be reduced (YC6H4NO2). Incorporation of electron-withdrawing Y in the aromatic ring of YC6H4NO2 increases the conversion, indicating that the kinetics of this process is similar to that for the carbonylation of nitrobeznene by CO in the absence of water (described in J. Mol. Catal. A: Chem. 2011, 337, 9-16). Surprisingly, the incorporation of electron-withdrawing substituents into the aromatic ring of the XnPy ligand also increases the conversion of YC6H4NO2 (regardless of the structure of the YC6H4NO2 substrate).