title: A coordinatively flexible hexadentate ligand gives structurally isomeric complexes M2(L)X3 (M = Cu, Zn; X = Br, Cl).
abstract: Polypyridyl multidentate ligands based on ethylenediamine backbones are important metal-binding agents with applications in biomimetics and homogeneous catalysis. The seemingly hexadentate tpena ligand [systematic name: N,N,N'-tris(pyridin-2-ylmethyl)ethylenediamine-N'-acetate] reacts with zinc chloride and zinc bromide to form trichlorido[μ-N,N,N'-tris(pyridin-2-ylmethyl)ethylenediamine-N'-acetato]dizinc(II), [Zn2(C22H24N5O2)Cl3], and tribromido[μ-N,N,N'-tris(pyridin-2-ylmethyl)ethylenediamine-N'-acetato]dizinc(II), [Zn2Br3(C22H24N5O2)]. One Zn(II) ion shows the anticipated N5O coordination in an irregular six-coordinate site and is linked by an anti carboxylate bridge to a tetrahedral ZnX3 (X = Cl or Br) unit. In contrast, the Cu(II) ions in aquatribromido[μ-N,N,N'-tris(pyridin-2-ylmethyl)ethylenediamine-N'-acetato]dicopper(II)-tribromido[μ-N,N,N'-tris(pyridin-2-ylmethyl)ethylenediamine-N'-acetato]dicopper(II)-water (1/1/6.5) [Cu2Br3(C22H24N5O2)][Cu2Br3(C22H24N5O2)(H2O)]·6.5H2O, occupy two tpena-chelated sites, one a trigonal bipyramidal N3Cl2 site and the other a square-planar N2OCl site. In all three cases, electrospray ionization mass spectra were dominated by a misleading ion assignable to [M(tpena)](+) (M = Zn(2+) and Cu(2+)).
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, Odense 5230, Denmark.
authors.forename: Christina
authors.initials: C
authors.lastname: Wegeberg
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, Odense 5230, Denmark.
authors.forename: Vickie
authors.initials: V
authors.lastname: McKee
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, Odense 5230, Denmark.
authors.forename: Christine J
authors.initials: CJ
authors.lastname: McKenzie
keywords: ESI mass spectrometry; biomimetics; copper; crystal structure; ethylenediamine backbone; hexadentate ligand; homogeneous catalysis; polypyridyl ligands; structural isomery; tpena; zinc