David E. Fenton

The activation of small molecules by dinuclear complexes of copper and other metals

Revue synthetique concernant la reactivite de complexes avec des coordinats divers (macrocycles, bases de Schiff, heterocycles azotes), vis a vis de O 2 , CO 2 H 2 O 2 etc... Synthese bibliographique

Heterodinuclear metal complexes of phenol-based compartmental macrocycles

Abstract This article concerns recent progress in the derivation of heterodinuclear metal complexes from phenol-based compartmental macrocycles. Focus is placed on the design of unsymmetrical macrocycles whose two metal-binding sites, sharing two phenolic oxygens, are dissimilar with respect to the cavity size, coordination number, or the nature of donor atom. The stereochemistry, physicochemical properties and reactivities of the heterodinuclear complexes derived from these compartmental macrocycles are reviewed.

METAL COMPLEXES OF BIBRACCHIAL SCHIFF BASE MACROCYCLES

Abstract This article discusses polynuclear metal complexes of Schiff base macrocycles and their potential application to the modelling of metallobiosites, in particular di- and tri-nuclear copper(II)-containing sites. A brief perspective of the area is presented and then the article addresses the development of pyridinyl-derived bibracchial (doubly pendant-armed) Schiff base macrocycles and their metal complexes. The cleft-like configurations of the complexes bear resemblance to the metal-containing pockets present in metalloproteins. A ‘first generation’ model for the trinuclear copper site in ascorbate oxidase, and a dinuclear manganese(II) complex bearing a single acetato-bridge, and which may have relevance to the modelling of dinuclear manganese biosites, are discussed. An extension of the work to thiophene-derived macrocycles and their dicopper(I) complexes is also presented.

Lanthanide complexes of some macrocyclic schiff bases derived from pyridine-2,6-dicarboxaldehyde α,ω-primary diamines

Abstract The synthesis of macrocyclic lanthanide complexes via the reaction of pyridine-2,6-dicarboxaldehyde with 1,2-diaminoethane, 1,2-diaminopropane and 1,3-diaminopropane in the presence of lanthanide nitrates as templating agents is discussed together with the use of the lanthanum derivatives in transmetallation reactions with copper(II).

A coordination polymer derived from the copper(II) complex of a bis-(salicylhydrazone) derived from iminodiacetic acid diethyl ester

Abstract A coordination polymer bearing alternate mononuclear and phenoxy-bridged dinuclear copper(II) motifs has been synthesised from a bis-(salicylhydrazone) derived from the diethyl ester of iminodiacetic acid. The structure of the polymer has been established by X-ray crystallography.

Dicopper(II,II) and dicopper(I,II) complexes of a series of dinucleating macrocycles

The dinucleating macrocycles H2Lm,n containing two 2,6-di(aminomethyl)-4-methylphenol entities combined through two alkane chains, (CH2)m and (CH2)n, at the amine nitrogens have been prepared for the (m,n) sets (2,3), (2,4), (2,5), (3,3) and (3,4). The dinuclear copper(II) complexes having general formula [Cu2Lm,n][ClO4]2 have been prepared. Cryomagnetic investigations (80–300 K) reveal a strong antiferromagnetic spin-exchange between the copper(II) ions within each complex (J based on ℋ=–2JS1S2 in the range –345 to –255 cm–1). The cyclic voltammograms show two reduction couples, CuIICuII–CuICuII and CuICuII–CuICuI. The comproportionation constants Kcom for the mixed-valence CuICuII complexes have been determined electrochemically. The Kcom value increase in the order of the macrocycles (L2,3)2– < (L2,4)2– < (L2,5)2– and (L3,3)2– < (L3,4)2–. The CuICuII mixed-valence state is shown to be ‘spin-trapped’(Class I) for all the complexes based on ESR spectra.

The syntheses, properties and crystal and molecular structures of the copper(II) and nickel(II) complexes of the non-symmetric schiff bases, derived from 1,2-diaminoethane, pentane-2,4-dione and 2-pyrollecarboxaldehyde

Abstract The synthesis of a non-symmetric Schiff base derived from 1,2-diaminoethane, pentane-2,4-dione and 2-pyrollecarboxaldehyde is described and the copper(II) and nickel(II) complexes are reported. The crystal structure of the nickel(II) complex is monoclinic, R = 0.0368, 1451 reflections: the crystal structure of the copper(II) complex is isomorphous, ( R = 0.0387, 1239 reflections). In both structures, the metals adopt square-planar coordination geometries and long intermolecular contacts lead to weak oligomerisation. The EPR spectra of the copper(II) complex is discussed and related to the structure.

Formation of axial phenolate–metal bonds in square-pyramidal complexes

Copper(II) complexes derived from tripodal ligands capable of forming 5,6,6- or 5,5,6-membered chelate ring sequences have been synthesised and characterised. The crystal structures of two complexes [CuL-(O2CBut)]·MeCN [HL =(2-hydroxy-5-nitrophenylmethyl)(pyridin-2-ylethyl)(pyridin-2-ylmethyl)amine] and [CuL(O2CMe)]·H2O [HL =(2-hydroxy-5-nitrophenylmethyl)bis(pyridin-2-ylmethyl)amine] have been solved. They are neutral, mononuclear copper(II) species in the solid state. In contrast to copper(II) complexes derived from related tripodal ligands forming 6,6,6-membered chelate rings, the present complexes have an axial phenolate–copper(II) bond in their square-pyramidal structures. The formation of this bond is related to the steric factors arising from the flexibility of the ligand pendant arms. The complex [CuL(O2CMe)] exhibits structural features related to the biosite in galactose oxidase; an acetate co-ordinates to copper equatorially and a phenolate oxygen atom occupies the axial position.

Metal complexes of some tetraketones and their schiff bases

Abstract Metal complexes of the tetraketones N-(o-tolyl)-diacetoacetamide (H 2 L a and 1,1′-(2,6-pyridyl)bis-1,3-butanedione (H 2 L b ) are reported. The reaction of H 2 L b with hydroxyalkyl- and hydroxyarylamines to yield Schiff bases (H 4 L) is given and metal complexes of the type, M 2 L, M(H 4 L)X 2 and M 2 (H 2 L)X 2 have been prepared. The properties of the metal complexes are discussed and suggested structures presented.

Manganese(II) and iron(III) complexes of the tridentate ligands bis(benzimidazol-2-ylmethyl)-amine (L1) and -methylamine (L2). Crystal structures of [MnL1(CH3CO2)2], [FeL2Cl3], and [Fe2L12(µ-O){µ-(CH3)3CCO2}2][ClO4]2

The preparation and characterisation of [MnL1(CH3CO2)2](1), [Mn6(µ4-O)2(C6H5CO2)10(H2O)4](9), [FeL1Cl3](10), [FeL2Cl3](2), and [Fe2L12(µ-O){µ-(CH3)3CCO2}2][ClO4]2(3) are reported where L1 and L2 are bis(benzimidazol-2-ylmethyl)amine and bis(benzimidazol-2-ylmethyl)methylamine. The molecular structures of (1), (2), and (3) were determined by X-ray diffraction. Complex (1) exists as a discrete, neutral, mononuclear species in the solid state. The manganese(II) ion is five-co-ordinate with the tridentate ligand bound in a meridional manner. Both acetates are monodentate with Mn–O distances of 2.076(5) and 2.158(5)A. Complex (9) contains a [Mn6(µ-O)2]10+ core, formally 4MnII :2MnIII. Complex (2) is neutral, mononuclear, distorted octahedral. The ligand co-ordinates in a similar manner to that seen in (1) and the chlorides occupy the three remaining meridional sites, with Fe–Cl(equatorial) 2.318(5)A and Fe–Cl(axial) 2.322(5) and 2.433(5)A. The Mossbauer spectrum of (10) at room temperature comprises a quadrupole doublet: δ= 0.40(1), ΔEQ= 0.33(2) mm s–1. Complex (3) is a dinuclear iron(III) species containing the triply bridged [Fe2(µ-O)(µ-RCO2)2]2+ core. The Fe ⋯ Fe distance is 3.075(5)A and the Fe–O(oxo)–Fe angle is 117.0(6)°. The high-spin iron(III) centres are antiferromagnetically coupled with J=–116 cm–1. The Mossbauer spectra of (3) at room temperature and 70 K consist of doublets with δ= 0.44(1), ΔEQ= 1.37(2), and δ= 0.55(1), ΔEQ= 1.30(2) mm s–1 respectively.