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

[摘要] English: A number of triazolecyclooctadienemetal(l) complexes of the type[M(LL')(cod)] (where M = Ir or Rh and LL' represents the differentbidentate N-N'- donor atom ligands, such as bpt-Nl+ and bpt) aswell as their oxidative addition products [M(LL')(cod)(Me)(I)] havebeen prepared and characterised by IR, ¹H NMR and elementalanalyses. It was found that in general these complexes aremonomeric 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 linearrelationships were found indicating second order kinetics. All of thekinetic data had zero intercepts (within experimental error)indicating that no reverse reactions occur. The reactions werecarried out in different solvents to study the influence of solventproperties on the reaction rate.The reactions were also conducted at different temperatures tocalculate the activation parameters. These indicated an associativemechanism as what is usually expected from these types ofcomplexes.The ability of the LL' bidentate ligands to increase the Lewisbasicity of the metal center are reflected in the values of thesecond order rate constants. From this we can compile thefollowing series indicating the different bidentate ligands' donatingcapabilities:macsm> AnMetha > hpt > bpt-Nl+ > sacac> tfaa > cupf > bpt'The activation ability of the bpt-Nl+ ligand for oxidative addition tothe metal center is better than that of the bpt ligand given thecorrect solvent and metal center are chosen. It seems that in thecase of the [M(bpt-NH)( cod)] complexes the rhodium analogue ismore 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.

[发布机构] University of the Free State