Grzegorz Romanowski

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.

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.

Crystal structure and magnetic properties of catena-μ-(pyrazine-N,N′)bis[(p-nitrobenzoyl)trifluoroacetonato-O,O′]copper(II)

Abstract The X-ray crystal structure, variable-temperature magnetic susceptibilities and e.s.r. spectra are reported for the title complex. The complex crystallises as infinite chains in which the copper(II)-β-diketonate units are bridged axially by ambidentate pyrazine ligands with a Cu⋯Cu separation of 7.6700(2) A. The magnetic susceptibility measurements in the range 5–325 K are consistent with the ferromagnetic intrachain exchange. The S =1/2 Heisenberg ferromagnetic linear chain analysis results in magnetic parameters of g =2.12 and J/k =0.6 K.

Potentiometric, spectrophotometric, and AM1d studies of the equilibria between silver(I) ion and monoaza-crown ethers with anthraquinone in various solvents

Complex formation and stability constants between silver(I) and monoaza-12-crown, monoaza-15-crown, and monoaza-18-crown ethers with anthraquinone were determined in acetonitrile, methanol, and propylene carbonate by potentiometric and UV-spectrophotometric methods. Complexes of 1 : 1 and 1 : 2 metal-to-ligand stoichiometry were formed. The solvent composition and the size of the macrocyclic ring affect the stability constants of the complexes. The energetically most favorable structures of the 1 : 1 metal-to-ligand complexes were calculated and visualized by the AM1d method at a semiempirical level of theory.

Nickel(II) and palladium(II) complexes with singly condensed diprimary triamines and 2-aminobenzaldehyde

Abstract Six new nickel(II) and one palladium(II) complexes are obtained by complexation of unsymmetrical Schiff bases HA, HD and HB resulting from 1:1 condensation of 2-aminobenzaldehyde with 1,5-diamino-3-azapentane, 1,7-diamino-4-azaheptane and 1,7-diamino-4-methyl-4-azaheptane, respectively. NiAX (X=Cl, NO3, ClO4), NiBI, and Ni(HD)X2 (X=Cl, NO3) display an alternation of configuration at the metal center from planar, over pseudohedral to octahedral when going from A, through B, to D containing complexes, as indicated by the variation in their spectroscopic and magnetic properties. NiAX complexes retain their planar structure in solution, whereas NiBI solutions show a weak paramagnetism in consequence of a rapid (on the NMR time-scale) equilibrium between low spin (S=0) planar and high spin (S=1) close to tetrahedral forms. Crystal structures of NiAClO4 and NiBI obtained by X-ray diffraction studies revealed a planar coordination in the former and a planar-to-tetrahedral distorted metal configuration with an angle between N1, Ni, N2 and N3, Ni, N4 planes of 41° in the latter compound. An intermolecular charge transfer transition accounting for an absorption of solid NiAClO4 in the 600–800 nm region, which is unusual for planar nickel(II) complexes, has been postulated.

{2-[1-(2-Amino-2-methyl­propyl­imino)eth­yl]phenolato-κ3N,N′,O}dioxidovanadium(V)

In the crystal structure of the title compound, [V(C12H17N2O)O2], the vanadium(V) centre is five-coordinate in a distorted square-pyramidal environment. The three atoms of the deprotonated Schiff base and a double-bonded O atom comprise the basal plane. N—H⋯O hydrogen bonds lead to a zigzag chain structure parallel to [001].

Spectrophotometric and AM1d studies of the equilibria between oxidovanadium(IV) and four isomers of n-propyl-3-azido-2,3-dideoxy-d-hexopyranosides in aqueous solution

Abstract Complex formation and stability constants for complexes between isomers of n-propyl-3-azido-2,3-dideoxy-d-hexopyranosides and oxidovanadium(IV) were determined in aqueous solution by the spectrophotometric method. Complexes of 1 : 2 metal-to-ligand stoichiometry were formed. The impact of the structures of the ligands on the complex formation was discussed. The energetically most favorable structures of the complexes were calculated and visualized by the AM1d method at the semi-empirical level of theory.

Di-μ-oxido-bis­({2-[(R,R)-(−)-(2-amino­cyclo­hexyl)imino­meth­yl]-4-nitro­phenolato-κ3N,N′,O}oxidovanadium(V)) dimethyl sulfoxide disolvate

The title compound, [V2(C13H16N3O3)2O4]·2C2H6OS, is a centrosymmetric dimeric complex solvated by two dimethyl sulfoxide molecules. Each VV atom is six-coordinated by one oxide group, two N atoms and one O atom from the tridentate Schiff base ligand, and by two additional bridging O atoms in a distorted octahedral coordination geometry. Three atoms of the cyclohexane ring are each disordered over two sites, with occupancy factors of 0.501 (10) and 0.499 (10). C—H⋯O and N—H⋯O hydrogen bonds link the dimers and solvent molecules into a supramolecular network.

Di-μ-oxido-bis­({(R)-(–)-2-[1-(2-amino­propyl­imino)eth­yl]-1-naphtholato-κ3 N,N′,O}oxidovanadium(V))

In the title dinuclear compound, [V(2)(C(15)H(17)N(2)O)(2)O(4)], each V(V) atom is six-coordinated by one oxide group, and by two N and one O atom of the tridentate Schiff base ligand, and bridged by two additional oxide O atoms, resulting in a centrosymmetric dimer. The metal centre has a distorted octa-hedral coordination with the monoanionic Schiff base ligand occupying one equatorial and two axial coordination positions. The separation between V atoms is 3.214 (3) Å. In the crystal structure, there are N-H⋯O, C-H⋯O and C-H⋯π hydrogen bonds, and π-π inter-actions.

Di-μ-oxido-bis­{[(R,R)-(+)-1-amino-2-(3-methoxy-2-oxidobenzyl­ideneamino-κ2O2,N)-1,2-diphenyl­ethane-κN]oxidovanadium(V)} dihydrate

In the crystal structure of the title compound, [V2(C22H21N2O2)2O4]·2H2O, oxide-bridged dimers of the complex are linked to water molecules by hydrogen-bonding interactions. The two five-membered chelate rings in the dimeric molecule both adopt twist conformations. Each VV atom is six-coordinated by one oxide group and by two N and one O atom of the tridentate Schiff base ligand, and is bridged by two additional oxide atoms. The metal centre has a distorted octahedral coordination. The monoanionic ligands occupy one equatorial and two axial positions.