Unusual CuII and MnII Complexes of Phenol‐Based Ligands Containing Amine, Pyridine and Formyl Functions: Unexpected Structural Features and Solution Studies

The phenol-based ligand Hpy2ald containing formyl, amine and pyridine functions reacts with copper(II) nitrate, copper(II) bromide and manganese(II) chloride to yield complexes with unexpected structures. In contrast to previously reported coordination compounds with similar ligands, the carbonyl group of the ligand in all complexes does not coordinate to the metal ions. The metal-to-ligand ratio is 2:1 in the case of the copper(II) nitrate complex and 1:1 in the case of the copper(II) bromide and manganese(II) chloride complexes. The copper(II) nitrate complex exhibits both donor-atom and coordination number asymmetry, as one copper ion is pentacoordinate with an N3O2 donor set, and the other one is hexacoordinate with an O6 donor set. In the latter two complexes, the phenol group of the ligand remains protonated and fails to bridge the two metal ions; instead it is semi-coordinated to only one metal ion. This results in the formation of mononuclear complexes in which copper(II) or manganese(II) ions have a distorted square-pyramidal surrounding. All complexes were structurally, spectroscopically and magnetically investigated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)