Synthesis and Structure of Novel RuII-NC-Me Complexes and Their Activity Towards Nitrile Hydrolysis: An Examination of Ligand Effects

MOLA, JOAQUIN; PUJOL, DAVID; RODRÍGUEZ, MONTSERRAT; ROMERO, ISABEL; SALA, XAVIER; KATZ, NÉSTOR; PARELLA, TEODOR; BENET-BUCHHOLZ, JORDI; FONTRODONA, XAVIER; LLOBET, ANTONI

AUSTRALIAN JOURNAL OF CHEMISTRY

CSIRO Publishing

Lugar: Collingwood, Vic.; Año: 2009 vol. 62 p. 1675 - 1683

0004-9425

The synthesis and isolation of new Ru(II)-acetonitrile complexes, of general formula trans,fac-[Ru(bpea)(B)(MeCN)](BF4)2 (bpea = N,N-bis(2-pyridylmethyl)ethylamine; B = bpy, 2,2'-bipyridine, 4; B = dppe, 1,2-diphenylphosphinoethane, 5), together with a synthetic intermediate trans,fac-[Ru(NO3)(bpea)(dppe)](BF4), 6, are described. Ru(bpea)Cl3, 1, is used as the starting material for the synthesis of all complexes 2-5 presented in this paper that are characterized by analytical, spectroscopic (IR, UV/Vis, 1D and 2D NMR), and electrochemical techniques (Cyclic voltammetry). Furthermore, complexes 4, 5 and 6 have also been characterized in the solid state by monocrystal X-ray diffraction analysis. Their structures show a distorted octahedral geometry where the bpea ligand bonds in a facial mode, the didentate ligands bpy and dppe bond in a chelate manner and finally the MeCN or the NO3- ligand occupy the sixth position of the octahedral Ru metal center. The kinetics of the basic hydrolysis of the coordinated MeCN ligand for complexes 4, 5 and a for a related complex [Ru(phen)(MeCN)([9]- aneS3)](BF4)2, 7, containing the 1,4,7-trithiacyclonane ligand ([9]aneS3) and 1,10- phenanthroline (phen) is also described. Second-order rate constants measured at 25 oC of k = 1.01 x 10-3 M-1s-1 for 4, 1.08 x 10-4 M-1s-1 for 5 and 6.8 x 10-3 M-1s-1 for 7, have been obtained, through UV-Vis spectroscopy. Activation parameters have also been determined over the temperature range 25.0-45.0 oC and agree with a mechanism that involves an associative rds. Finally the electronic and steric influence of the auxiliary ligands for the above and related complexes is discussed.