Electrochemical and spectroscopic studies of tungstencarbonyl complexes containing nitrogen and phosphorous ligands

Abstract

Este trabalho tratou da síntese, caracterização espectroscópica e do comportamento eletroquímico dos compostos [W(CO) 4 (bipy)] (1), [W(CO) 3 (bipy)(dppm)] (2) e [W(CO) 3 (bipy)(dppf)] (3), bipy = 2,2'-bipiridina; dppm = bis(difenilfosfina)metano; dppf = 1,1'-bis(difenilfosfina)ferroceno. Os dados provenientes das espectroscopias no infravermelho e de RMN 31 P{ 1 H} mostraram que o tungstênio apresenta uma geometria de coordenação octaédrica com as fosfinas atuando como ligantes monodentados. Os estudos eletroquímicos foram realizados empregando-se as técnicas de voltametria cíclica e coulometria a potencial controlado. Os voltamogramas cíclicos mostraram que os carbonil complexos contendo ligantes fosforados apresentam uma maior estabilidade frente à oxidação do que o composto (1).The present work deals with the synthesis, spectroscopic investigation and electrochemical behaviour of the compounds [W(CO) 4 (bipy)] (1), [W(CO) 3 (bipy)(dppm)] (2) and [W(CO) 3 (bipy)(dppf)] (3), bipy = 2,2'-bipyridine; dppm = bis(diphenylphosphino)methane; dppf = 1,1'-bis(diphenylphosphino)ferrocene. The IR and 31 P{ 1 H} NMR spectroscopic data have shown an octahedral coordination geometry for the tungsten atom with the diphosphines acting as monodentate ligands. The electrochemical behaviour of the complexes was investigated by cyclic voltammetry and controlled potential coulometry. Cyclic voltammograms have indicated that the compounds containing diphosphines ligands are more stable towards oxidation than compound (1).

Untitled

“…Stability towards oxidation is gained by the presence of the diphosphines. 122 The compound [Mo(CO) 3 (PF 3 ) 3 ] was originally described as occurring only in the mer-form, on the basis of IR spectra. This was an unexpected result, and a reinvestigation using high-field 19 F and 31 P NMR, including computer simulations, has shown that in solution this compound occurs as a mixture of mer-and fac-isomers.…”