Iron(II) Complexes of Chiral Tridentate Nitrogen Donors and their Application in Catalytic Hydrosilylation Reactions

Abstract

Enantiomerically pure, C2‐symmetric 2,6‐bis(pyrazol‐3‐yl) pyridine ligands were obtained by treatment of diethyl‐2,6‐pyridinedicarbonate with (1R,4R)‐(+)‐camphor in the presence of NaH followed by ring closure with hydrazine. After twofold N‐alkylation at the pyrazole rings, the addition of iron(II) chloride led to the according pentacoordinate dichloridoiron(II) complexes. All intermediates of the ligand synthesis, the ligands bearing NCH3 and NCH2C6H5 groups and the derived iron(II) complexes were structurally characterized by means of X‐ray structure analysis. In‐situ reaction with iron(II) carboxylates resulted in the formation of iron(II) carboxylate complexes, which turned out to be highly active in the hydrosilylation of acetophenone. However, even at room temperature, the enantiomeric excess of the product 1‐phenylethanol is poor. 57Fe Mössbauer spectroscopy gave an insight into the species formed during catalysis.