Giampietro Cum

Preparation and analysis of ε-caprolactam and ε-thiocaprolactam platinue(II) and rhodium(III) complexes

Abstract The synthesis and properties of some Pt(II) and Rh(III) complexes with e-caprolactam (L) and e-thiocaprolactam (L′) are reported. The compounds, L 3 RhCl 3 , L 2 PtCl 2 , [L′ 4 RhCl 2 ]Cl and [L′ 4 Pt]Cl 2 , have been characterized by chemical analysis, infra-red, n.m.r. and electronic spectra, X-ray powder diffraction and electrical conductance. Evidence is presented for coordination of the unidentate ligands through the oxygen or sulfur atoms. Configurational assignments indicate trans-coordination in both the square-planar L 2 PtCl 2 and octahedral L 3 RhCl 3 complexes.

Palladium catalysts supported on oligomeric aramides in the liquid-phase hydrogenation of phenylacetylene

Abstract The catalytic behaviour of palladium supported on oligomeric aramides has been investigated in the liquid phase selective hydrogenation of phenylacetylene to styrene, by comparison with conventional Pd-supported systems, such as Pd/carbon. Pd/Al 2 O 3 and Pd/SiO 2 . The influences of the reduction temperature and metal loading on the activity/selectivity behaviour of the title reaction are explained in terms of different reducibility patterns of the catalysts, as well as in the light of a peculiar support effect of the organic matrix on Pd particles.

Thermal isomerization of photochemically synthesized (Z)-9-styrylacridines. An unusually high enthalpy of Z→E conversion for stilbene-like compounds

Eight stable (Z)-9-styrylacridines, have been photochemically synthesized and their enthalpies of thermal isomerization (ΔHZ→E) determined by means of thermal analysis. The enthalpy values were found to be influenced by both electronic and steric effects. The title compounds were used as models in order to gain insight into the energetic implications involved in the Z→E isomerization process and its applicability to photochemical energy conversion by irradiation in the visible wavelength region.

A high enthalpy value in thermal isomerization of photosynthesized cis-9-styrylacridines

Four stable stilbene-like cis-isomers - i.e. 9-styrylacridines - were photosynthesized and their ΔH cis → trans thermal isomerization determined.

Polymer-supported catalysts: preparation and characterisation of complexes between palladium derivatives and oligomeric aramides

Abstract Oligomeric aramides of the phenyleneterephthalamide structural type, impregnated with Pd salts, have been prepared and characterized. For a better understanding of the type of interactions between Pd and these oligomers, the corresponding monomeric model compound and simpler molecules have been investigated by several techniques. The results obtained establish that a coordination complex is formed through a specific linkage between Pd and the primary amino groups present as chain terminals both in the macromolecular species as well as in the model compound. No evidence has been found of significant bond interactions involving either carboxyl or secondary amido groups.

Synthesis and characterization of an hexamethylphosphortriamide derived palladium complex: Crystal structure of dichloro bis(dismethylamine)palladium(II)

When a solution of palladium(II) chloride in hexamethylphosphortriamide (HMPA = (Me 2 N) 3 PO) was heated, a sec-alkylamine (L) palladium complex —of the type PdL 2 Cl 2 — was isolated and characterized on the basis of analytical and spectral data. The crystal structure of the title compound was carried out by X-ray diffraction data: it crystallizes in a monoclinic cell P2 1 /c, with a = 7.699(2), b = 5.999(1), c = 10.454(3) A, β = 98.3(1)dg, Z = 2. Final R values: R = 0.035 and R w = 0.035 for 1059 independent reflections. A trans square planar coordination geometry around the palladium atom was ascertained. An alternative synthetic route to the complex is reported, together with the possible reasons for its formation.

Palladium-based catalysts supported on oligomeric aramides. A TPR investigation

Abstract The reduction pattern of PdCl2 supported on oligomeric aramides has been investigated by temperature programmed reduction (TPR) measurements in the range of temperature −80 to 305°C. The influence both of chemical composition of the oligomeric matrix and Pd loading has been ascertained. A peculiar metal—support interaction greatly affects the reducibility of Pd, allowing its stabilisation in the oxidised form (i.e., Pd2+).

Effect of static pressure on the ultrasonic activation of chemical reactions. Selective oxidation at benzylic carbon in the liquid phase

The effects of sonoactivation on kinetic rates and chemical yields of a model reaction, selective oxidation at the benzylic site of indane, was studied at subatmospheric static pressures ranging from 200 to 760 Torr. The reaction occurs at a rate up to five times higher when a suitable ultrasonic field activates the reagents in solution. By varying the pressure applied to the system, the total sonochemical yields were found to follow a non-monotonic trend, with a peak value related to the frequency of ultrasounds irradiated. According to the general theory of acoustic cavitation, the results obtained are accounted for in terms of distribution and dynamics of the cavitating bubbles, whose average radius of equilibrium reaches its resonant value when tuned to a definite value of pressure, so allowing the best coupling with the ultrasonic field; under these conditions, the sonocatalytic effects on reaction parameters are maximized.

Hydrodealkylation of toluene over polyamide-based catalysts

Abstract The activity and selectivity of poly-p-phenyleneterephthalamide based platinum, palladium and rhodium catalysts was studied in the hydrodealkylation reaction of toluene. With respect to conventional PdC, PtC and PtAl2O3 catalysts, the hydrodealkylation over the new catalysts occurs at lower temperatures. The polyamide-based systems show a very low hydrogenating activity. A mechanism for hydrogenolysis of toluene over polyamidecatalysts is proposed.

1,2-Oxazolidines. Part V. Spiro and condensed biheterocyclic isomers from nitrones and 1,3-oxazolidin-2-ones

The cycloaddition reaction between nitrones and substituted 1,3-oxazolidin-2-ones yields condensation products and spiro-compounds, each type of product containing a 1,2-oxazolidine nucleus. Their stereochemistry was elucidated by lanthanide shift analysis. The main spectrometric characteristics and the chemical behaviour of these new systems are discussed. Evidence is reported that the formation of the two types of isomeric adduct is controlled by a rearrangement process in competition with the cycloaddition.