The characterisation and kinetic study of rhodium(I) and iridium(I) triazole complexes

English: A number of triazolecyclooctadienemetal(l) complexes of the type [M(LL')(cod)] (where M = Ir or Rh and LL' represents the different bidentate N-N'- donor atom ligands, such as bpt-Nl+ and bpt) as well as their oxidative addition products [M(LL')(cod)(Me)(I)] have been prepared and characterised by IR, ¹H NMR and elemental analyses. It was found that in general these complexes are monomeric containing one LL' and cod ligand respectively. The oxidative addition between CH31 and the studied metal(l) complexes have been investigated on a UVNis . spectrophotometer. Under pseudo-first order conditions linear relationships were found indicating second order kinetics. All of the kinetic data had zero intercepts (within experimental error) indicating that no reverse reactions occur. The reactions were carried out in different solvents to study the influence of solvent properties on the reaction rate. The reactions were also conducted at different temperatures to calculate the activation parameters. These indicated an associative mechanism as what is usually expected from these types of complexes. The ability of the LL' bidentate ligands to increase the Lewis basicity of the metal center are reflected in the values of the second order rate constants. From this we can compile the following series indicating the different bidentate ligands' donating capabilities: macsm> AnMetha > hpt > bpt-Nl+ > sacac> tfaa > cupf > bpt' The activation ability of the bpt-Nl+ ligand for oxidative addition to the metal center is better than that of the bpt ligand given the correct solvent and metal center are chosen. It seems that in the case of the [M(bpt-NH)( cod)] complexes the rhodium analogue is more reactive, while the opposite case' is observed for the- [M(bpt)(cod)] complexes. Thus the bpt-Nl+ ligand is the better 0- donor in the rhodium complex, while the bpt ligand is the better 0- donor in the iridium complex.