Metal benzoylpivaloylmethanates. Part III. Manganese(III) and iron(III) chelates

Summary The synthesis and principle properties of several novel tris[1-(4-X-phenyl)-4,4-dimethylpenta-1, 3-dionato]-iron(III) and manganese(III) complexes, where X=MeO, Me, H, F, Cl and NO₂, are described. Magnetic susceptibility measurements in the 4.2–295 K range show a near Curie behaviour and a constant magnetic moment for manganese(III) complexes and for iron complexes, with X=F, Cl or NO₂. Iron complexes with ligands having substituents: X=MeO, Me and H, show weak antiferromagnetic interaction (J=ca.–8 cm^–1 for the two former compounds) and a decrease in magnetic moment with decreasing temperature. In both manganese(III) and iron(III) complexes the diketonate ligand can be easily replaced by chlorine. Equilibrium constants could be evaluated only for substitution of the third diketonate ligand by chloride in the iron complexes on the basis of spectrophotometric measurements. For manganese chelates, the replacement of the second diketonate by chloride is accompanied by reduction of manganese(III) manganese(II) and free organic radical formation is observed.     

Metal benz oylpivaloylmethanates,part I. Free ligands and copper(II) chelates

Summary Syntheses and properties ofpara-substituted benzoylpivaloylmethanes and their copper(II) chelates are described.¹H n.m.r., u.v. and i.r. spectra of free ligands indicate a very high enol content. Molecular weight determin tions showed that the bulky t-butyl and phenyl groups do not prevent association of chelates in chloroform solutions. All the chelates obey the Curie-Weiss law with the Weiss constant close to zero; magnetic moments lie within the 1.87–2.02 B.M. range over the 77–300 K range. I.r. and Raman spectra suggest that the complexes have a square planar stereochemistry and a trans geometrical structure.Reprints of this article are not available.     

Metal Complexes with Macrocyclic Ligands. Part XLI. Nickel(II) and copper(II) complexes with mono-N-functionalized dithiadiazamacrocycles

Three N₂S₂ macrocycles ( 3, 10, 12 ) carrying an amino group as a pendant arm have been synthesized and their complexation properties towards Ni²⁺ and Cu²⁺ studied. The crystal structures of the Cu²⁺ complexes with 10-methyl-1,4-dithia-7,10-diazacyclododecane-7-ethanamine ( 3 ) and 11-methyl-1,4-dithia-8,11-diazacyclotetradecane-8-ethanamine ( 10 ) show that, in both cases, the Cu²⁺ is pentacoordinated by the four donor atoms of the macrocycle and the amino group of the side chain. In aqueous solution, however, two forms of the complexes with stoichiometries [MLH] and [ML] (M = Cu²⁺ or Ni²⁺) have been observed. In [MLH], the amino group is protonated and does not bind to the metal ion, whereas in [ML] the amino group is bound, and a pentacoordinated geometry results. The pK_a values for the equilibrium [ML] + H⁺?[MLH]⁺ decrease in the order 12 > 10 > 3 , indicating that the 2-aminoethyl side chain binds better to the Cu²⁺ than the 3-aminopropyl side chain. Cyclic voltammetry for the Cu²⁺/Cu⁺ pair shows that the 2-aminoethyl pendant arm stabilizes the Cu²⁺ oxidation state, when the metal ion is in the 14-membered ring ( 10 ), whereas it stabilizes Cu⁺ for the 12-membered macrocycle ( 3 ).     

Metal chelates of heterocyclic Nitrogen containing ketones. XV. Five-coordinate nickel(II) and copper(II) complexes with a sulphur-nitrogen tridentate schiff base

Summary Complexes of the Schiff base, 2-picolylphenylketone-hydrazine-S-benzyl dithiocarbazate, PPKBzTE, with nickel(II) and copper(II) halides have been prepared and characterized using spectral (¹H n.m.r., i.r., uv-visible and e.s.r.) and magnetic measurements. A square pyramidal geometry is assumed for [Ni(PPKBzTE-H)X]₂(X=Cl or. Br) and a square planar structure for [Ni(PPKBzTE-H)I]. The spectral studies in inert solvents show the presence of temperature dependent equilibria between tetrahedral and five-coordinate species in the chloro-and bromo-complexes. The interaction of nickel(II) complexes with various heterocyclic nitrogen Lewis bases yielded distorted octahedral 12 adducts. Copper(II) complexes, [Cu₃(PPKBzTE)(PPKBzTE-H)Cl₅] and [Cu(PPKBzTE-H)Br]₂ were separated and associated with a five-coordinate structure. Variable temperature magnetic susceptibility and the spectral studies showed that they are trimeric and dimeric, respectively.Abstracted from his Ph.D. Thesis.     

Spectroscopic studies of zinc(II)tetraphenylporphyrin molecular complex with 1,4-dioxane

The molecular complex of zinc(II)tetraphenylporphyrin with 1,4-dioxane has been obtained. The IR spectra of the [Zn(TPhP)(1,4-dioxane)2] stabile molecular complex between 4000 and 50cm(-1) have been studied. An interpretation is given on the base the "chair" conformation of 1,4-dioxane molecule.     

Iron(II), cobalt(II), nickel(II) and copper(II) chelates of 1,1′-Dibenzoylacetylferrocene

Summary 1,1-Dibenzoylacetylferrocene (DBAFc) complexes of iron(II), cobalt(II), nickel(II) and copper(II) have been prepared and characterized. The physical properties of the complexes are discussed on the basis of uv-visible, Mössbauer spectra and magnetic measurements.     

Metal compounds in free-radical processes. II. Interaction of copper (II) chelates of N-alkylnorephedrines with peroxides and 2,2′-diphenyl-1-picrylhydrazyl

The reactions of the copper (II) chelates of norephedrine (I), N-methylnorephedrine (II), N-ethylnorephedrine (III), and N-n-butylnorephedrine (IV) with benzoyl peroxide, cumene hydroperoxide, and 2,2′-diphenyl-1-picrylhydrazyl have been studied. Only the chelates of N-alkyl-substituted norephedrines enter into the reactions with free radicals, while their reactivity increases with the length of the alkyl substituent in the amino group of the ligand. The decomposition of cumene hydroperoxide was catalyzed by all four chelates; the catalytic efficiency increases in the order I<II<III < IV.     

Metal chelates of ligands containing the ONS donor grouping,Part II. Metal chelates of schiff bases derived from β-diketones and α-N-Methyl-S-methyldithiocarbazate

Summary The Schiff bases RC(OH)=CHC(R)=NNMeC(S)SMe (R = Ph,p-MeC₆H₄, R = Me; R = R = Ph) have been prepared by condensation of -diketones with -N-methyl-S-methyldithiocarbazate. By the loss of a proton they act as singly negatively charged tridentate ligands with oxygen, nitrogen and sulphur donor atoms (ONS). Iron forms the high-spin complexes [Fe^III(ONS)₂][Fe^IIICl₄]. Copper(II), palladium(II), and platinum(II) yield the square-planar 1 : 1 complexes, M(ONS)CI (M = Cu, Pd, Pt) and Cu(ONS)NO₃. Cobalt(II) and nickel(II) form high-spin, six-coordinate 1 : 2 complexes, M(ONS)₂. For M = Ni and R = R = Ph, the complex is high-spin and octahedral, but when R = Ph orp-MeC₆ H₄ and R = Me, the complexes are diamagnetic and square-planar with nitrogen and sulphur (NS) coordinatio of the Schiff base, indicating that a change in the Rgroup can bring about a change in spin-state and stereochemistry of nickel.Part I: see ref. 1.     

Metal chelates in vinyl polymerization. II. Mechanism of initiation by Fe(DPM)3

The nature of the interaction between the unsaturated monomer and the chelate, Fe(DPM)₃, is studied in detail. The interaction is found to occur only in solution. The stoichiometry of interaction and the equilibrium constant are evaluated. With the help of spectral evidence, attempts are made to point out the specific sites of interaction.     

Metal Complexes with Macrocyclic Ligands. Part XLIII. Tetraazamacrocyclic nickel(II) and copper(II) complexes with aliphatic methylthio- and methoxy-substituted pendant chains

The 14-membered tetraazamacrocyclic Ni²⁺ and Cu²⁺ complexes of 4 (1, 4, 8-trimethyl-11-[(2-methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), 5 . (1, 4-dimethyl-8, 11-bis[2-(methylthio)ethyl]-l, 4, 8, 11-tetraazacyclotetradecane), and 7 (1, 4, 8, ll-tetrakis[2-(methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), with pne, two, and four methylthio-substituted pendant chains, respectively, and the Ni²⁺ complex of 6 (1, 4-dimethyl-8, 11-bis (2-methoxyethyl)-1, 4, 8, 11-tetraazacyclotetradecane), with two methoxy-substituted pendant chains, were synthesized and their chemistry studied with regard to modelling F430. Solution spectra in H₂O, MeCN, and DMF indicate participation of the side chain in metal coordination when the donor group is a thioether, whereas no coordination with the metal ion is observed with the ether group. Similarly the X-ray structures of the thioether-containing compounds [Ni( 5 )](ClO₄)₂, [Cu( 5 )](ClO₄)₂, and [Cu( 7 )](ClO₄)₂ show a coordination number of 5, whereas that of [Ni( 6 )](ClO₄)₂ with ether pendant chains, shows a coordination number of 4. Cyclic voltammetry of these complexes in MeCN reveals that Ni²⁺ is reversibly reduced to Ni⁺ between ?0.64 and ?0.77 V vs. SCE, the potential being influenced by the nature and number of the pendant chains. At more negative potentials, the thioether is cleaved, whereby a thiol is formed; the thiol is then oxidized at ca. + 0.8 V vs. SCE, when a glassy carbon electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in [Ni( 6 )](ClO₄)₂ is observed under similar conditions.     

Iron(II), cobalt(III), nickel(II) and copper(II) chelates of furan and thiophene azo-oximes

Summary Complexes of furan and thiophene azo-oximes with iron(II), cobalt(III), nickel(II) and copper(II) have been prepared and characterised. Iron(II), cobalt(III) and copper(II) complexes are diamagnetic in the solid state. The diamagnetism of the copper(II) chelates is suggestive of antiferromagnetic interaction between two copper centres.¹H n.m.r. spectral data suggest atrans-octahedral geometry for the tris-chelates of cobalt(III). Nickel(II) complexes are paramagnetic, in contrast to the diamagnetism of the analogous complexes of arylazooximes. The electronic spectra are suggestive of octahedral geometry for the iron(II), cobalt(III) and nickel(II) complexes, andD _4h -symmetry for copper(II). Infrared data indicate N-bonding of the oximino-group to the metal ions.     

Metal complexes of phytohormones. Part II. Copper(II) complexes of 6-benzylaminopurine

Summary Copper(II) complexes with 6-benzylaminopurine (BAPH) of the types Cu(BAPH)₂(ClO₄)₂·2H₂O (1) Cu(BAP)₂·4H₂O (2), and Cu(BAPH₂)Cl₃·MeOH (3), have been synthesized and characterized by conductivity, magnetic measurements, i.r., electronic and e.s.r. spectroscopy.     

Thermal decomposition of copper(II) glutarate trihydrate. Part I. The mechanism of dehydration of copper(II) glutarate trihydrate

The mechanism of thermal dehydration of copper(II) glutarate trihydrate has been determined from the analysis of the kinetic data for isothermal and non-isothermal dehydration experiments. Microscopic investigations for the dehydration process of a single crystal of copper(II) glutarate trihydrate have been carried out to support the mechanism. The simultaneous DTG—DTA—TG curves of the salt are also described.     

Metal Complexes with Macrocyclic Ligands. Part XXXVIII. Steric effects in the copper(II) and nickel(II) complexes with tetra-N-alkylated 1,4,8,11-tetraazacyclotetradecanes

A series of tetra-N-alkylated 1,4,8,11-tetraazacyclotetradecanes have been synthesized and their complexation potential towards Ni²⁺ and Cu²⁺ studied. In the case of sterically demanding alkyl substituents, such as i-Pr, PhCH₂, or 2-MeC₆H₄CH₂, no metal complexes are formed, whereas for substituents such as Me, Et, and Pr, the metal ion is incorporated into the macrocycle. The spectroscopic properties of the Ni²⁺ and Cu²⁺ complexes in aqueous solution indicate that, depending on the sterical hindrance of the N-substituents, the complexes are either square planar or pentacoordinated. All these Ni²⁺ and Cu²⁺ complexes react with N to give ternary species, the stability of which have been determined by spectrophotometric titrations. The tendency to bind N decreases with increasing steric hindrance of the alkyl substituents. The X-ray studies of the Ni²⁺ complex with the macrocycle 11 , substituted by two Me and two Pr groups, and that of the Cu²⁺ complex with the tetraethyl derivative 8 show that in the solid state, the metal ions exhibit square planar coordination with a small distortion towards tetrahedral geometry.     

Ion-association compounds of anionic surfactants with iron(II)chelates: Part II. Selective determination of surfactants

Homologous anionic surfactants may be separated from each other by solvent extraction of their ion-association compounds with iron(II) chelates. Separations of components from a number of surfactant mixtures were investigated, and the effect of solution variables on extraction and separation was studied. A method is proposed for the determination of surfactants of various chain lengths. Applications of this method to synthetic mixtures and to biodegradation experiments are described.