Franco Zingales

Kinetic studies of group VII metals carbonyls-IV-dimerisation and substitution reactions of Mn(I) and Re(I) pentacarbonyl halides.

Abstract Carbon monoxide replacements on rhenium pentacarbonyl halides with different neutral, mono- and bidentate entering groups are reported. The reactions proceed by a dissociation pathway, and the rate constants change with the nature of the halogen in the order Cl>Br>I. The dependence of the rate constants on the temperature has also been determined. For these reactions a mechanism is proposed which involves as a rate-determining step the formation of a five-coordinated intermediate, Re(CO) 4 X, followed by a rapid reaction with the reagent ligand. The rates of formation of the rhenium and manganese dimeric, halogen-bridged tetracarbonyl compounds from the parent pentacarbonyl halides have also been determined. In these reactions an equilibrium is reached, which favours the monomeric form. The mechanism appears to be rather complicated and the dimerisation probably occurs through the same five-coordinated intermediate, M(CO) 4 X. The rate of dimerisation in n-heptane varies in the order: Cl>Br>I and, for a given halide, Mn>Re.

Organometallic phosphazenes: synthesis and characterization of Pt(II) and Pt(0) cinnammonitrile cyclophosphazene derivatives

Abstract Hexakis(4-formylphenoxy)cyclophosphazene has been reacted with (cyanomethylene)triphenylphosphorane to yield the hexakis(4-cinnammonitrile phenoxy)cyclophosphazene compound. The cinnammonitrile moieties have been used to bind six {(PPh3)2Pt} fragments on the olefin groups, six trans-{Pt(PPh3)2(CF3)} to the nitrile groups and both Pt(0) groups to yield compounds 2, 3 and 4, respectively.