Carlo Busetto

Catalysts for low-temperature methanol synthesis. Preparation of Cu-Zn-Al mixed oxides via hydrotalcite-like precursors

Cu-Zn-Al-mixed oxides are well known as catalysts for methanol synthesis at low temperature. An in-depth investigation into the nature and characteristics of a ternary compound (Mg/sub 6/Al/sub 2/(OH)/sub 16/CO/sub 3/ x 4H/sub 2/O) and its evolution with the calcination temperature until the formation of the oxide phases was carried out. X-ray patterns of the pure hydrotalcite-like phase calcinated at different temperatures (90/sup 0/-45/sup 0/C) and also ESR spectra at this range were reported. After calcination at 350/sup 0/C for 24 hours, the total decomposition of the precursors, with the formation of CuO and ZnO was revealed by X-ray diffraction. There was no evidence of the presence of free Al/sub 2/O/sub 3/. 4 figures, 2 tables.

Paramagnetic anisotropy in cobalt(II) Schiff-base complexes. X-Ray crystal structure and electron spin resonance of NN′-ethylenebis-(acetylacetoneiminato)cobalt(II)-doped NN′-ethylenebis(acetylacetone-iminato)nickel(II)

The e.s.r. study of a single crystal of NN′-ethylenebis(acetylacetoneiminato) cobalt(II)-doped NN′-ethylenebis-(acetylacetoneiminato) nickel(II), [Co(acacen)] and [Ni(acacen)], is reported; determination of the ground state of the cobalt complex was attempted. [Ni(acacen)] Is isomorphous with [Co(acacen)] as shown by a single-crystal structural determination: the doped crystals are orthorhombic, space group Pna21, Z= 4, a= 12.18(1), b= 10.28(1), and c= 10.37(1). The equatorial principal axes of the g tensor were found to be almost parallel with the cobalt–ligand bond, rather that between these bonds, as expected.

Electronic and magnetic properties of the inactive form of the complex NN′-ethylenebis(salicylideneiminato)cobalt(II), and of five-co-ordinate complexes of cobalt(II) with Schiff's bases

The dimeric structure of the inactive form of the complex [Co(salen)][salen =NN′-ethylenebis(salicylideneiminato)] has been confirmed by e.s.r. measurements. From electronic and magnetic properties the structure of the complex seems to be intermediate between those of monomeric planar [Co(salen)] and square-pyramidal [Co(salen)], pyridine. All the features due to five-co-ordination are already present, so there is no electronic reason for the inactivity of the complex towards oxygen.

New adducts of phthalocyaninatocobalt(II) with pyridine and 4-methylpyridine and their vibrational, magnetic, and electronic properties. Part I. Reactivity towards oxygen

Different reaction temperatures have allowed the isolation of 1 : 1 and 1 : 2 adducts of phthalocyaninatocobalt(II) with pyridine and 4-methylpyridine. Thermal, vibrational, and magnetic-susceptibility analyses have provided useful information about the structural properties of these complexes; e.s.r. and electronic spectra have permitted a detailed investigation of the ligand-field levels of the cobalt atom. All the adducts react with oxygen and form, at low temperatures, well characterized Co : O2 1 : 1 adducts.

Optically active complexes of Schiff bases. Part II. Complexes of cobalt(II) with tetradentate Schiff bases and their reactivity with oxygen

Complexes of cobalt(II) with Schiff bases obtained by condensation of salicylaldehyde with substituted ethylenediamines have been synthesised together with five-co-ordinated pyridine adducts. E.s.r., electronic, and c.d. spectra and magnetic susceptibilities have been reported. Energy level schemes have been calculated by a ligand field approach in order to fit the magnetic properties and allow an assignment of the observed absorption bands. The reaction with oxygen has been studied and discussed in terms of both the electron configuration of the cobalt atom and the steric effects of substituents on the carbon atoms of the substituted ethylenediamines.

New adducts of phthalocyaninatocobalt(II) with 3-methylpridine and pyridazine and their vibrational, magnetic, and electronic properties. Part II. High-spin adducts

The tendency to six co-ordination and the strength of the intermolecular interaction in phthalocyaninatocobalt(II) are discussed with reference to the properties of its adducts with 3-methylpyridine and with pyridazine. The various span states of (3-methylpyridine)pathalocyaninatocobalt(II) strongly resemble those found in the haem group on changing the axial lignad.