EXAFS study of the local structure of lead complex in ionic liquids

Under the condition of ultra diluted concentration omega[ Pb(OAc)(2)] or omega[Pb(OAc)(4)] < 0. 2%, the local structure of lead complex dissolved in ionic liquids has been studied by Pb L-m-edge EXAFS. PV4+ in bulk Pb(OAc)(4) shows 8 nearest oxygen neighbors at (0. 200 +/- 0.003) ran while Pb2+ in bulk Pb (OAc)(2) shows 6 nearest oxygen neighbors at (0.225 +/- 0.003) mn. However, both Pb4+ and Pb2+ dissolved in ionic liquids have very low coordination numbers, normally less than 4, indicating a low coordination property for the ionic liquids. On the other hand, the interatomic distance between Pb center and the nearest oxygen seems not comparable with each other. For example, the Pb-O distance observed for Pb4+ in [ bmim] PF6 is only (0.186 +/- 0.005) nm with a very low coordination number of 2.4, while the Fourier transform clearly indicates a second coordination shell for Pb4+ in [bmim]PF6. The Pb-O distance observed for Pb2+ in [bmim] PF6, which is only (0. 211 +/- 0.005) nm, is also significantly shorter than that (0.225 nm) in bulk Pb ( OAc )(2). The Pb ions dissolved in [bmim] BF4, which are 0.223 nm for Pb2+ and 0.210 nm for Pb4+ respectively, exhibit that the Pb-O distances are of no more difference with those in bulk samples.