Synthesis and structural characterization of five-, six-, and seven-coordinate mononuclear manganese(II) complexes with N-tridentate ligands

A series of four mononuclear manganese (11) complexes with the N-tridentate neutral ligands 2,2':6,2"-terpyridine (terpy) and N, N-bis(2-pyridylmethyl)ethylamine (bpea) have been synthesized and crystallographically characterized. The complexes have five- to seven-coordinate manganese(II) ions depending on the additional ligands used. The [Mn(bpea)(Br)(2)] complex (1) has a five-coordinated manganese atom with a bipyramidal trigonal geometry, while [Mn(terpy)(2)](I)(2) (2) is hexa-coordinated with a distorted octahedral geometry. Otherwise, the reactions of Mn(NO3)(2).4H(2)O with terpy or bpea afforded novel seven-coordinate complexes [Mn(terpy)(NO3)(2)(H2O)] (3) and [Mn(bpea)(NO3)(2)] (4), respectively. 3 has a coordination polyhedron best described as a distorted pentagonal bipyramid geometry with one nitrate acting as a bidentate chelating ligand and the other nitrate as a monodentate one. 4 possesses a highly distorted polyhedron geometry with two bidentate chelating nitrate ligands. These complexes represent unusual examples of structurally characterized complexes with a coordination number seven for the Mn(II) ion and join a small family of nitrate complexes. (C) 2004 Elsevier B.V. All rights reserved.