Experimental and theoretical study of the kinetics of dissociation in cis-[RuCl2(P-P)(N-N)] type complexes

• Autor(a) principal: Monteiro,Marcos C. R.
• Data de Publicação: 2010
• Outros Autores: Nascimento,Fabio B., Valle,Eliana M. A., Ellena,Javier, Castellano,Eduardo E., Batista,Alzir A., Machado,Sergio de Paula
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532010001000027
• topic: DFT; ruthenium complexes; trans-effect; kinetics; dissociation

The substitution reactions [RuCl2(P-P)(N-N)] + L → [RuCl(L)(P-P)(N-N)]+ + Cl-, where P-P = 1,4-bis(diphenylphosphino)butane and N-N = 2,2´-bipyridine, 4,4´-dimethoxy-2,2´-bipyridine, 4,4´-dimethylpyridine-2,2´-bipyridine and 4,4´-dichloro-2,2´-bipyridine, L = pyridine (py) or 4-methylpyridine (4-pic), were studied under pseudo-first order conditions. The reactions proceeded by means of a dissociative mechanism. The rate constants of the substitution reactions increased as the pKa of the N-heterocyclic ligands increased and as the oxidation potential of the metal center decreased. The greater the participation of the atomic d orbitals of the metal in the HOMO, according to DFT calculations, the easier is the dissociation of the chloride from the coordination sphere of the complex. In the 31P{¹H} NMR spectra of the series of complexes of general formula [RuCl(L)(P-P)(N-N)]PF6, there are two doublets with Δ&#963; < 1. This is consistent with products formed by dissociation of the chloride trans to one of the phosphorus atoms in the precursors.