Agatino Spadaro

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.

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.

Selective synthesis of alkynes by catalytic dehydrogenation of alkenes over polymer-supported palladium acetate in the liquid phase

A heterogenized palladium acetate catalyst, in the presence of oxygen and perchloric acid in theanol–water caused the direct conversion of terminal and internal monoalkenes into the corresponding alkynes, under mild conditions and in high yields; Wacker-type ketonization occurs with the same reagents in dioxane–water.