Crystal structures and magnetic properties of Ni-bisdithiolene complexes with decamethylmetallocenium cations

Three new compounds of formula (1), (2), and (3) have been synthesised, and structurally and magnetically characterised (dmit²⁻ = 1,3-dithiol-2-thione-4,5-dithiolato; dmid²⁻ = 1,3-dithiol-2-one-4,5-dithiolato). Their structural features and magnetic behaviours are compared with those of and . The result of this is that the interactions between the Ni(dmit)₂ units in 1 are of ferromagnetic-type, as suggested previously for . The change from acetonitrile to acetone when going from to 2 results in stronger ferromagnetic intermolecular interactions. This better cooperativity is due to a significant increase of the number of contacts between the various moieties within the . On the contrary, the inclusion of larger solvents such as benzonitrile in this type of complexes results in a totally different structural arrangement, which leads to an antiferromagnetic behaviour for 3.     

Kinetics and mechanism of the oxidation of oxalic acid by tetrachloroaurate(III) ion

The oxidation of oxalic acid by tetrachloroaurate(III) ion in 0.005 ? [HClO₄] ? 0.5 mol dm⁻³ is first order in and a fractional order in [oxalic acid], the reactive entities being AuCl₃(OH)⁻ and ions. The pseudo first-order rate, k_obs, with respect to [Au(III)], is retarded by increasing [H⁺] and [Cl⁻]. The retardation by H⁺ ion is caused by the dissociation equilibrium . A mechanism in which a substitution complex, is formed from AuCl₃(OH)⁻ and ions prior to its rate limiting disproportionation into products is suggested. The rate limiting constant, k, has been evaluated and its activation parameters are reported. The equilibrium constant K₁ for the formation of the substitution complex and its thermodynamic parameters are also reported.