title: Iron coordination chemistry with new ligands containing triazole and pyridine moieties. Comparison of the coordination ability of the N-donors.
abstract: We report the synthesis, characterization, and solution chemistry of a series of new Fe(II) complexes based on the tetradentate ligand N-methyl-N,N'-bis(2-pyridyl-methyl)-1,2-diaminoethane or the pentadentate ones N,N',N'-tris(2-pyridyl-methyl)-1,2-diaminoethane and N,N',N'-tris(2-pyridyl-methyl)-1,3-diaminopropane, modified by propynyl or methoxyphenyltriazolyl groups on the amino functions. Six of these complexes are characterized by X-ray crystallography. In particular, two of them exhibit an hexadentate coordination environment around Fe(II) with two amino, three pyridyl, and one triazolyl groups. UV-visible and cyclic voltammetry experiments of acetonitrile solutions of the complexes allow to deduce accurately the structure of all Fe(II) species in equilibrium. The stability of the complexes could be ranked as follows: [L(5)Fe(II)-py](2+) > [L(5)Fe(II)-Cl](+) > [L(5)Fe(II)-triazolyl](2+) > [L(5)Fe(II)-(NCMe)](2+), where L(5) designates a pentadentate coordination sphere composed of the two amines of ethanediamine and three pyridines. For complexes based on propanediamine, the hierarchy determined is [L(5)Fe(II)-Cl](+) > [L(5)Fe(II)(OTf)](+) > [L(5)Fe(II)-(NCMe)](2+), and no ligand exchange could be evidenced for [L(5)Fe(II)-triazolyl](2+). Reactivity of the [L(5)Fe(II)-triazolyl](2+) complexes with hydrogen peroxide and PhIO is similar to the one of the parent complexes that lack this peculiar group, that is, generation of Fe(III)(OOH) and Fe(IV)(O), respectively. Accordingly, the ability of these complexes at catalyzing the oxidation of small organic molecules by these oxidants follows the tendencies of their previously reported counterparts. Noteworthy is the remarkable cyclooctene epoxidation activity by these complexes in the presence of PhIO.
authors.affiliation: Institut de Chimie Moléculaire et des Matériaux d'Orsay, Université Paris Sud, F-91405 Orsay, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Ségaud
authors.forename: Jean-Noël
authors.initials: JN
authors.lastname: Rebilly
authors.forename: Katell
authors.initials: K
authors.lastname: Sénéchal-David
authors.forename: Régis
authors.initials: R
authors.lastname: Guillot
authors.forename: Laurianne
authors.initials: L
authors.lastname: Billon
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Baltaze
authors.forename: Jonathan
authors.initials: J
authors.lastname: Farjon
authors.forename: Olivia
authors.initials: O
authors.lastname: Reinaud
authors.forename: Frédéric
authors.initials: F
authors.lastname: Banse
mesh_terms: D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D017672:Nitrogen Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D014230:Triazoles / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D017672:Nitrogen Compounds; D011725:Pyridines; D014230:Triazoles; D007501:Iron; C023666:pyridine