P. Alessandro Vigato

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.

The preparation and crystal structure of N,N′-bis(salicylidene)-1,5-diamino-3-thiapentane-dioxouranium(VI)

Abstract The title compound has been prepared and crystallized from acetonitrile. The crystals are ortho rhombic, space group Pcab, with a = 18.91(2), b = 16.13(2), c = 12.10(1) A, z = 8. The structure was determined from MoKα diffractometer data by standard methods and refined to R = 0.066. The coordination geometry of the uranium atom is a pentagonal bipyramid with the pentadentate ligand coordinated in the plane normal to the uranyl group. The UO (ligand) bonds (mean 2.25 A) are shorter than the UN bonds (2.60 A). The sulphur atom is significantly displaced from the equatorial plane and makes with uranium a bond of 2.96 A.

The template synthesis and crystal and molecular structure of a sexidentate Schiff-base macrocyclic complex of samarium(III), [Sm(C18H18N6)(NO3)(OH)(H2O)]NO3·2MeOH

The template condensation of 2,6-pyridinedicarbaldehyde with ethylenediamine in the presence of Sm(NO3)3 gave a complex formulated as [Sm(C18H20N6O)(NO3)3]. The complex was recrystallised from water and the X-ray crystal structure determined by the heavy-atom method and refined by least squares to a final R value of 0.073. The recrystallised compound can be formulated as the title complex. The Sm3+ cation is enclosed in the cyclic ligand and bonded to its six N atoms as well as to a bidentate NO3– anion, to one OH– anion, and to a water molecule: Some O ⋯ O contact distances can be ascribed to hydrogen bonds; the clathrate solvent molecules are disordered.

Complexes of ligands providing endogenous bridges. Part 5. Solution studies on a novel ‘3 + 3’ hexamine Schiff-base macrocyclic complex of lanthanum

Structural studies in solution show that when lanthanum nitrate is used as a template in the reaction of 2,6-diacetylpyridine and 1,3-diamino-2-hydroxypropane a ‘3 + 3’ macrocycle containing three lanthanum ions is the predominant species formed. Hydrogen-1 n.m.r. decoupling and n.O.e. difference spectroscopy confirms the presence of a two-fold axis of symmetry where two ‘sides’ of the macrocycle are identical and different from the third.

DIOXOURANIUM(VI) COMPLEXES WITH 2,6-DIFORMYL-4-CHLOROPHENOL

Abstract The ligand H(DIAL) reacts with uranyl acetate to form the complexes [UO2(DIAL)2.H2O], and [VO2(DIAL)2.MeOH]. Vhermal degradation of the adducts yields two different [UO2(DIAL)2] species as intermediates. The compounds have been characterized by infrared and 1H nmr spectroscopy and by thermogravimetric measurement.

Preparation and crystal structure of a copper(II) homobinuclear chelate

SummaryThe structure of the homobinuclear complex Cu2(aapen)H2O, where aapen is the tetraanionic ligand derived from the condensation of 1,2-diaminocthane witho-acetoacetylphenol, has been determined from diffractometer data and refined to R = 6.1%. The crystals are monoclinic,P21/c, witha = 12.991(5),b = 8.530(4),c = 18.546(6) Å, andβ = 104.10(4)°; Z = 4. The ligand employed has two different coordination sets of atoms, N2O2 and O2O2, two oxygen atoms being common to both donor sets. In the complex, one copper atom is retained in the plane of the inner N2O2 chamber whilst the other, which is incorporated in the outer O2O2 chamber, is five-coordinate, being axially bonded to a water molecule.

Synthesis and crystal structure of bis(dimethylthioacetonedicarboxylate)nickel(II)

SummaryThe title compound has been synthesized and characterized. The crystal structure has been determined by single-crystal x-ray analysis from diffractometer data, and refined to R= 0.063 for 1889 observed reflections. Crystals are monoclinic, space group P21/n, witha=21.97(2),b=8.21(1),c=10.44(1) A, and β=101.87(3), and Z=4. Both ligands are coordinated to nickel through sulphur and one oxygen atom to realize thecis form of the complex in the square planar coordination geometry. Bond distances are: Ni-S, 2.14(1), Ni-O, 1.87(1) and 1.90(1) Å. Each nickel atom also forms two close contacts with oxygen atoms from adjacent molecules.

Metal complexes of binucleating ligands derived from 2,6-diformyl- and 2,6-diacetyl-4-methylphenol

Abstract The preparation and complexing properties towards Cu(II), Ni(II) and UO 2 (VI) of acyclic and macrocyclic Schiff base ligands derived from the reaction of 2,6-diformyl- and 2,6-diacetyl-4-methyl- phenol with the facultative diamine 1,5-diamino-3- oxapentane and the functionalised diamine 1,3-di- amino-2-hydroxy-propane are discussed.

Mononuclear barium and dinuclear copper(II) complexes of a 24-membered bibracchial tetraimine Schiff-base macrocycle derived from N,N-bis(2-aminoethyl)-2-methoxyethylamine

The X-ray structure of a mononuclear barium complex of the bibracchial tetraimine Schiff-base macrocycle derived from the cyclocondensation of 2,6-diacetylpyridine and N,N-bis(2-aminoethyl)-2-methoxyethylamine [monoclinic, space group P2/n(no. 13), a= 27.494(20), b= 14.120(13), c= 21.024(14)A, β= 91.68(57)°, Z= 8] confirms that the macrocycle folds to present a molecular cleft within which the metal is co-ordinated. Transmetallation with CuII gives a homodinuclear copper(II) complex the crystal structure of which [monoclinic, space group P21/c, a= 14.807(6), b= 9.558(4), c= 17.432(8)A, β= 113.89(5)°, Z= 2] shows that the copper(II) atoms are held by the ‘head’ units of the macrocycle, an opening of the cleft having occurred.

Transition metal complexes with new acyclic Schiff bases

Abstract New acyclic Schiff bases derived from the condensation of o-methoxyphenylbutane-1,3-dione or o-methoxyphenylpentane-1,3-dione with ethylenediamine have been prepared and characterized and mononuclear copper(II), nickel(II) and vanadyl(IV) complexes of these ligands have been synthesized. The crystal structure of the nickel complex with the latter ligand has been determined from X-ray data. The crystals are triclinic, space group P 1 , with (cya) = 12.27(1), (cyb) = 11.40(1), (cyc) = 8.50(1) A , α = 98.2(2), β = 95.5(2), and γ = 95.6(2)°. The metal ion is bonded to the inner N 2 O 2 donor set of the ligand and is approximately square planar.