Reactivity of Pd(dppm)(CO) and Pd(dppm)(CO)(RCCR) (n = 0, +1, +2) Towards F. Evidence of Reactive Intermediates and X-Ray Structure of [Pd(dppm)(MeOCC≡CCOMe)(F)]PF

The reactivity of the trinuclear palladium cluster [Pd(dppm)(CO)] (dppm = bis(diphenylphosphinomethane); n = 2, 1) towards F was investigated by electrochemical and spectroscopic methods. The reaction depends on the charge of the cluster. The chemical reduction of the cluster dication is observed in the presence of F generating the paramagnetic monocationic cluster. Spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) provided evidence for the radical F as an intermediate. In a similar manner to the dication, the monocationic cluster [Pd(dppm)(CO)] is also reduced, but in a slower process, by the F ion to produce [Pd(dppm)(CO)]. Additionally, the alkyne cluster adducts [Pd(dppm)(CO)(RCCR)] (n = 2, 1; R = COMe) are also reactive towards F. Particularly, the dication adduct leads to a metastable fluoride adduct [Pd(dppm)(CO)(RCCR)(F)]. The electroreductive behavior of this adduct involves electron-transfer steps and F exchange equilibriums, for which digital simulation enables the extraction of the thermodynamic parameters (standard potentials and equilibrium constants). Concurrently, the monocation adduct [Pd(dppm)(CO)(RCCR)] with F, leads to a disproponation generating 0. 5 equiv. of [Pd(dppm)(CO)(RCCR)(F)] and 0. 5 equiv. of [Pd(dppm)(CO)(RCCR)]. The former slowly evolves to [Pd(dppm)(RCCR)(F)], which was described by X-ray diffraction method. © 2010 Springer Science+Business Media, LLC.