M. Vidali

The preparation of binuclear complexes and their catalytic behaviour in the oxidation of 3,5-di-butycatechol

The complexes of type M(HL)2nH2O (n = 0, 1, 2,; M = Cu+, Ni+, Mn+, TiO+, Pd+; H2L = β,δ-triketones or β(ketophenols) have been prepared and characterized by elemental analyses and physico-chemical measurements. These mononuclear compounds were used as ligands to prepare homo - and heterobinuclear complexes. Magnetic moments and spectral data are reported. The copper(II) homo-dinuclear complexes have been tested as catalysts in the oxidation of 3,5-di-t-butylcatechol.

Preparation, properties and crystal structure of dioxane-bis-{μ-oxobis[oxo-vanadium(V) 2-(2′-hydroxypheny)iminomethylphenato]}

Abstract The title compound has been prepared by oxydation of vanadyl(IV) 2-(2′-hydroxyphynel)liminomethylphenato. The crystal structure has been determined by X-ray analysis from diffractometer data and refined to R 0.085. The crystals are triclinic, space group P 1 , with a = 12.98(1), b = 11.99(1), c = 11.97(1) A, α=94.12(4)°, β = 97.99(4)° and γ=102.13(4)°. Two five-coordinate vanadium atoms are oxygen bridged to form the binuclear asymmetric unit of the cell. Such units are additionally bridged in pairs by a dioxane molecule which makes two weak bonds with two symmetry related vanandium atoms forming a tetramer. Axial Vue5fbO distances are 1.55 and 1.56 A whereas Vue5f8O distances to the terminal oxygen atoms average 1.85 A and those to the bridging oxygens average 1.78 A. The Vue5f8O(dioxane) bond (2.51 A) is opposite to the axial bond.

Binuclear complexes of tetraketones

Abstract The tetraketones 1,1′-(1,3-phenylene)-bis-1,3-butanedione (H 2 L a ) and 1,1′-(1,4-phenylene)-bis-1,3-butanedione (H 2 L b have been isolated and characterised. They are potentially tetradentate ligands and H 2 L a could act as binucleating agent. The reaction of the tetraketones with different metal ions has been investigated. Homobinuclear complexes of the type (ML) 2 nS (S = H 2 O, MeOH or pyridine; n = 0, 1, 2, 4) have been prepared and characterised on the basis of analytical, i.r. and visible spectra, and magnetic susceptibility data. Metal complexes of 1,4-bis(acetoacetyl)-piperazine (H 2 L c ) have also been prepared.

Uranyl complexes with bidentate derivatives of pyridine N-oxide. The crystal structure of dimethylsulphoxidebis(1-oxo-2-thiopyridinato)dioxouranium(VI) and aquabis(1,2-dioxo-pyridinato)dioxouranium(VI) monohydrate

Abstract Some uranyl complexes with bidentate derivatives of pyridine-N-oxide have been prepared and their crystal structures determined by X-ray crystallography. Dimethylsulphoxidebis(1-oxo-2-thio-pyridinato)dioxouranium(VI) is monoclinic, space group P21/n with a = 18.70(2), b = 13.57(1), c = 6.87(1) A, and β = 99.80(3)°. Two bidentate ligands and one dmso molecule are equatorially bonded to the uranyl group in a distorted pentagonal bipyramidal coordination geometry. The Uue5f8O (equatorial) bond distances (mean 2.33 A) are of the same order and the Uue5f8S bond distances are 2.85 and 2.88 A. The Nue5f8O and the Nue5f8C bonds are partial double and Cue5f8S is double, suggesting the presence of a mesomeric distribution of electronic density over the ligand system. Aquabis(1,2-dioxopyridinato)dioxouranium(VI) monohydrate is orthorhombic, space group Pnam, with a = 12.26(1), b = 6.89(1) and c = 15.81(1) A. Two bidentate ligands and one water molecule are equatorially bonded to the uranyl group in the pentagonal bipyramidal coordination geometry. The Uue5f8O(equatorial) bond distances (mean 2.37 A) are of the same order and the Nue5f8O, Nue5f8C and Cue5f8O bonds are partial double. One additional water molecule is clathrate. The molecule has the Cs symmetry, with the uranyl group and the water oxygen atoms on the mirror plane.

Catalytic activity of vanadium(III) and oxovanadium(IV) complexes in the ziegler-natta synthesis of ethylenepropylene elastomers

Abstract Vanadium and oxovanadium(IV) complexes with β-diketones, β,δ-triketones, ketophenols and their Schiff bases were prepared and their performance as components of Ziegler-Natta catalysts in ethyleneue5f8propylene copolymerization were investigated. Attempted correlations of catalytic activity with the coordination geometry, coordination number of the vanadium, steric and electronic effect of the ligands do not give regular trends. No significant improvement on the features of the copolymer produced nor on the catalyst activity was found over the commonly known vanadium catalysts.

Preparation, characterization and reactivity of vanadyl(IV) and uranyl(VI) complexes with β,δ-triketones and ketophenols

Abstract Some β,δ-triketones and β-diketophenols have been prepared and characterized. A series of mononuclear oxovanadium(IV) adducts with these ligands have been isolated and characterized. All these mononuclear complexes have a free coordination set and may act as ligands towards a second metal ion. The syntheses of dinuclear complexes using the mononuclear ones as ligands are reported. Their stereochemistry is discussed on the basis of ir, uv and magnetic data. Mono- and dinuclear complexes were tested as ethylene-propylene copolymerization catalysts.

Synthesis and catalytic activity of alkoxyoxovanadium(IV) diketonates, crystal and molecular structure of bis-[methoxyoxovanadium(IV) acetylacetonate]

Abstract Methoxyoxovanadium(IV) acetylacetonate crystalizes in the monoclinic system, space group P2 1 /n, with a = 10.50(1), b = 11.10(1), c = 7.67(1) A, and β = 107.63(3)°. The complex consists of dimeric [VO(OCH 3 )acac] 2 units with molecular and crystallographic Ci symmetry, in which the vanadium atoms are in the tetragonal pyramidal coordination geometry. The Vue5fbO length is 1.587(3) A and all other Vue5f8O lengths are in the range 1.953(3)–1.968(3) A. The V V separation (3.104 A) compares well with metal-metal separations in binuclear complexes of atoms of comparable dimensions. The synthesis and the catalytic activity in ethylene-propylen co-polymerization of three other diketonates are reported.

Thorium complexes with bidentate ligands. Crystal structure of methanoltetrakis(1,2-dioxo-pyridinato)thorium(IV)

Abstract The X-ray crystal structure of the title compound has been determined from diffractometer data. The substance crystallizes in the triclinic system, space group P 1 , with a = 10.13(1), b = 13.89(1), c = 9.47(1) A, α = 82.85(3), β = 117.14(3) and γ = 107.05(3)°; D c = 2.06 g cm −3 for Z =2. The final conventional R was 0.052 based on the 5986 observed reflexions. Four bidentate ligands and one methanol molecule are bonded to thorium to form a distorted monocapped square antiprismatic coordination polyhedron. The Thue5f8O bond of 2.58 A to the uncharged solvent molecule is significantly longer than the eight Thue5f8O(L) bond distances (mean 2.45 A).

Crystal structure of 1-(2-hydroxyphenyl-3-(2-thiomethoxyphenyl)-1,3-propanedione), C16H14O3S

The crystal structure of the enol tautomer of 1-(2-hydroxphenyl)-3-(2-thiomethoxyphenyl)-1,3-propanedione C16H14O3S, was determined from X-ray crystallography. The finalR value was 5.99% based on 1945 unique observed reflections. The crystals are monoclinic,P21/c, witha=7.406(6),b=8.585(6),c=21.992(4) Å,β=93.42(2),Dc=1.36 g cm−3 forz=4. The compound is present in the solid state as a unique enol tautomer.There are two short, intramolecular O⋯O contacts of 2.553(4) and 2.577(4) Å. Both the phenol and the enol H atoms are asymmetrically located with respect to the O atoms.