Edmund Kwiatkowski

Metal complexes with unsymmetrical tetradentate schiff bases

Abstract A simple method for the synthesis of 1-amino-3-aza-4-methylhept-4-ene-6-one is presented. The dominant tautomeric form of the compound in CDCl 3 has been established. Using this compound eight (five new) unsymmetrical tetradentate Schiff bases and their nickel(II), palladium(II) and copper(II) complexes have been prepared and characterized by various physical techniques. Data for the complexes indicate that they are all of square-planar geometry. High resolution 1 H nmr studies, including lanthanide shift reagents on nickel and palladium chelates, allowed us to assign almost all proton resonances. Data for nickel(II) and palladium(II) chelates with 1-(2′-hydroxyphenyl)-1-phenyl-2,5-diaza-6-methylnona-1,6-diene-8-one are consistent with the ketoenamine structure of both the acetylacetone and hydroxybenzophenone portions of the molecules. Good resolved nitrogen hyperfine splitting was observed in the esr spectrum of the copper complex with the aforementioned ligand.

Dioxovanadium(V) Schiff base complexes of N-methyl-1,2-diaminoethane and 2-methyl-1,2-diaminopropane with aromatic o-hydroxyaldehydes and o-hydroxyketones: synthesis, characterisation, catalytic properties and structure

Abstract Nineteen new dioxovanadium(V) complexes with unsymmetrical tridentate Schiff base ligands, obtained by a single condensation of 2-methyl-1,2-diaminopropane or N-methyl-1,2-diaminoethane with salicylaldehyde and its derivatives, 2-hydroxy-1-naphthaldehyde, 2-hydroxyacetophenone, 1-hydroxy-2-acetonaphthone and 2-hydroxybenzophenone, were prepared. The complexes were characterized by their 1H and 51V NMR, IR, and UV–Vis spectra. Crystal structure of the 2-(4-amino-4-methyl-2-aza-1-penten-1-yl-κ2N)-3,5-dimethoxyphenolato-κO-dioxovanadium(V), VO2(C13H19N2O3), has been obtained by X-ray diffraction studies. The structure revealed a rarely encountered in VO2(tridentate Schiff base) complexes a distorted trigonal-bipyramidal coordination geometry. The complexes comprising ligands derived either from N-methyl-1,2-diaminoethane or 2-methyl-1,2-diaminopropane and 5-methoxysalicylaldehyde catalyse the oxidation of thioanisole to the corresponding sulfoxide by cumene hydroperoxide.

A convenient synthetic route to the monocondensation products of pentane-2,4-dione and aliphatic α,ω-diamines. Synthesis, x-ray structure and magnetic properties of a trinuclear copper(II) complex with 8-amino-5-aza-4-methyl-3-octene-2-one

A convenient synthesis of four, new, tridentate-N 2 O ligands which are monocondensation products of pentane-2,4-dione and aliphatic α,ω-diamines is described, and the basic properties of these ligands are reported. The reaction of one of them, 8-amino-5-aza-4-methyl-3-octene-2-one, HL 1 , with copper(II) perchlorate affords the trinuclear μ 3 -hydroxo bridged complex [(CuL 1 ) 3 (OH)](ClO 4 ) 2 . The single-crystal X-ray structure, spectroscopic and magnetic properties of this complex are described. The trinuclear cation consists of three CuL 1 subunits bound by a triply-bridging hydroxy group and three bridges formed by carbonyl oxygen atoms of three ligand molecules. Two trinuclear cations are held together within the unit cell by hydrogen bonding to the perchlorate anions. Crystallographic data: triclinic space group P (No. 2), a = 11.720(1), b = 12.283(2), c = 14.252(2) A; α = 71.78(1)°, β = 81.07(1)°, γ = 65.69(1)°, final R and R w factors are 0.0418 and 0.0536 respectively. Magnetic susceptibility data indicate a weak antiferromagnetic exchange within the trinuclear core with J = −15 cm −1 .

Unsymmetrical schiff base complexes of nickel(II) and palladium(II)

Abstract The unsemmetrical Schiff bases salicyladehyde-acetylacetoneethylenediimine (Hsal)(Hacac)en, o-hydroxyacetophenoneacetylacetoneethylenediimine(Hhap)(Hacac)en, o-hydroxybenzophenoneacetyl-acetoneethylenediimine(Hhbp)(Hacac)en, and their nickel(II) and palladium(II) complexes have been synthesized and studied by different techniques. Mass, pmr and double pmr spectra suggest that the free Schiff bases comprise two different hybridized nitrogen atoms. Diamagnetism and spectral data of Ni(II) and Pd(II) chelates are consistent with their square-planar stereochemistry. Pmr spectra indicate that a conjugation between aromatic rings in Ni(hbp)(acac)en and Pb(hbp)(acac)en favours the ketoamine form of the arromatic part of complexes rather than the normal Schiff base struture. Pmr spectrum of Ni(sa)(acac)en studied over the - 70°C, + 30°C range suggests a high flexibility of the five-membered chelate ring.

A novel unsymmetrical quadridentate ligand 1-(2′-aminophenyl)-6-methyl-2,5-diazanona-l,6-diene-8-one and its complexes with copper(II), nickel(II) and palladium(II)

Two routes for the preparation of the title compound (6) have been developed. Reaction of equimolar quantities of 2-aminobenzaldehyde, pentane- 2,4-dione and 1,2-diaminoethane yields the ligand 6 and 2-methyl-3-acetylquinoline as side product. The compound 6 was obtained in high yield in a one- step condensation of 2-aminobenzaldehyde with 1-amino-4-methyl-3-azahept-4-ene-6-one (5). Studies on the condensation of 5 with various 2-aminobenz- aldehyde derivatives revealed that the yield of unsymmetrical ligand is evidently influenced by the acidic properties of the hydrogen atom (of atoms) of the ring substituent in the ortho position to the carbonyl group. Copper(II), nickel(II) and palladium(II) complexes of 6 have been prepared and characterized. Spectroscopic data of nickel and palladium complexes are consistent with their planar structure. A superhyperfine splitting due to nitrogen is observed in the EPR spectrum of the copper complex in spite of the presence of azomethine hydrogen atom.

Synthesis, structure and magnetic properties of a new chloro-bridged dimeric copper complex, bis(μ-chloro)bis(8-amino-5-aza-4-methyl-3-octene-2-onato)dicopper(II)

Abstract The synthesis, structure and important properties of the title compound are reported. The complex, formulated as Cu2L2Cl2 (L=singly deprotonated 8-amino-5-aza-4-methyl-3-octene-2-one ligand), has a dimeric structure composed of two CuLCl subunits linked via bridging chlorine atoms. Each copper atom is five-coordinate in a distorted square-pyramidal coordination environment. The Cu2Cl2 structural core is characterized by an acute Cu-Cl-Cu′ angle of 82.9° and a short Cu-Cu′ separation of 3.418 A. Crystallographic data: monoclinic space group P21/c (No. 14), a=6.150(1), b=11.224(2), c=15.057(3) A; β=99.08(1)°; R=0.0222, Rw=0.0291. Magnetic susceptibility and magnetization measurements indicate ferromagnetic coupling of the copper(II) centers within the dimer, contrary to the predictions of a previously reported empirical correlation between the exchange energy, 2J, and structural factors.

Metal complexes with unsymmetrical tetradentate ketoenamines derived from β-diketones or ethoxymethylene-β-dicarbonyl compounds and 1-amino-4-methyl-3-azahept-4-ene-6-one

Abstract New preparative possibilities of the monocondensation product of pentane-2,4-dione and 1,2-diaminoethane for the synthesis of unsymmetrical ligands and their deuterated derivatives are demonstrated. Using this compound several new unsymmetrical tetradentate ketoenamines, various 9, 10, 11 substituted 4-methyl-5,8-diazaundeca-3,9-diene-2,11-diones and their copper(II), nickel(II) and palladium(II) complexes were obtained. On the basis of the 1 H nmr studies the structure of ligands and complexes were established. An unexpected stereochemistry was observed for the product of the reaction of 1,1,1-trifluoro-4-phenylbutane-2,4-dione with the mono-condensation product of pentane-2,4-dione and 1,2-diaminoethane. Spectroscopic data for the metal complexes are consistent with their planar structure. Utilizing the double resonance technique, deuteration of ligands, lanthanide and solvent shift reagents the assignment of almost all the 1 H nmr resources of ligands and complexes was accomplished.

New nickel(II) and palladium(II) complexes with unsymmetrical quadridentate Schiff bases derived from 8-amino-4-methyl-5-azaoct-3-en-2-one. Crystal and molecular structure of [4,10-dimethyl-3-(nitroso-χN)-5,9-(diaza-χ2N)-trideca-3,10-diene-2,12-(dionato-χO)(2–)]nickel(II)

A monocondensation product of pentane-2,4-dione and 1,3-diaminopropane, 8-amino-4-methyl-5-azaoct-3-en-2-one, has been used as a precursor in preparation of three new unsymmetrical quadridentate Schiff-base ligands comprising a trimethylenedi-imine moiety. Nickel(II) and palladium(II) complexes of these ligands have been obtained and characterized by spectroscopic techniques. They are of essentially square-planar geometry and diamagnetic. The single-crystal structure of (4,10-dimethyl-3-nitroso-5,9-diazatrideca-3,10-diene-2,12-dionato)nickel(II) has been determined and shows the co-ordination of nickel by a nitroso group through the nitrogen atom. Crystallographic data: space group P21/c(no. 14), a= 8.788(2), b= 7.562(2), c= 21.502(8)A, β= 98.49(2)°, final R and R′ 0.0422 and 0.0490, respectively.

Molecular structure and magnetic properties of bis(μ-chloro)bis[7-amino-4-methyl-5-azahept-3-en-2-onato(1−)]dicopper(II)

Abstract The molecular structure and magnetic properties of the title compound along with some other solid-state and solution properties are reported. The complex formulated as (CuLCl) 2 (L=singly deprotonated tridentate ligand 7-amino-4-methyl-5-azahept-3-en-2-one) is dimeric and consists of two identical CuLCl monomers wherein the copper center adopts a distorted square-pyramidal geometry. The monomers are bound together through two chloro bridges forming a four-membered planar central Cu 2 Cl 2 ring. The complex is weakly antiferromagnetic (2 J =−5 cm −1 and poorly fits to the previously reported empirical correlation linking J to the structural parameter Φ/ R in this class of compounds. Crystallographic data: monoclinic, P 2 1 / n , a =6.018(1), b =12.648(4), c =12.877(5) A, β=101.39(2)°, R =3.2%.

The optically active and racemic products of monocondensation of 1,2-diaminopropane and 2,4-pentadione as ligands and precursors for preparation of unsymmetrical Schiff bases and their nickel(II) complexes

Abstract The reaction of 2,4-pentadione with an excess of R-(−)-1,2-diaminopropane yields the optically active 4-methyl-7-amino-5-aza-3-octene, HL1. The compound has been used for further condensations with pyrrole-2-carboxaldehyde, pyridine-2-carboxaldehyde, 4-methyl-imidazole-5-carboxaldehyde and isoquinoline-3-carboxaldehyde to give unsymmetrical tetradentate Schiff bases H2L2, HL3, HL4 and HL5, respectively. All the tetradentate Schiff bases and the tridentate HL1 ligand react readily with Ni(II) to form optically active complexes, [NiL1(Mepy)]ClO4, [NiL1(Meim)]ClO4, NiL2, [NiL3–5]ClO4, where Mepy and Meim denote 4-methylpyridine and 1-methylimidazole, respectively. Using unresolved 1,2-diaminopropane as a starting material the racemic (±)NiL2 has also been obtained. All the complexes have been characterized by spectroscopic methods. The structure of (±)NiL2 has been determined by X-ray diffraction.