title: Intrinsic hydration of monopositive uranyl hydroxide, nitrate, and acetate cations.
abstract: The intrinsic hydration of three monopositive uranyl-anion complexes (UO(2)A)(+) (where A = acetate, nitrate, or hydroxide) was investigated using ion-trap mass spectrometry (IT-MS). The relative rates for the formation of the monohydrates [(UO(2)A)(H(2)O)](+), with respect to the anion, followed the trend: Acetate > or = nitrate >> hydroxide. This finding was rationalized in terms of the donation of electron density by the strongly basic OH(-) to the uranyl metal center, thereby reducing the Lewis acidity of U and its propensity to react with incoming nucleophiles, viz., H(2)O. An alternative explanation is that the more complex acetate and nitrate anions provide increased degrees of freedom that could accommodate excess energy from the hydration reaction. The monohydrates also reacted with water, forming dihydrates and then trihydrates. The rates for formation of the nitrate and acetate dihydrates [(UO(2)A)(H(2)O)(2)](+) were very similar to the rates for formation of the monohydrates; the presence of the first H(2)O ligand had no influence on the addition of the second. In contrast, formation of the [(UO(2)OH)(H(2)O)(2)](+) was nearly three times faster than the formation of the monohydrate.
authors.affiliation: Department of Chemistry, Wichita State University, Kansas 67620-0051, USA. mike.vanstipdonk@Witchita.edu
authors.forename: Winnie
authors.initials: W
authors.lastname: Chien
authors.forename: Victor
authors.initials: V
authors.lastname: Anbalagan
authors.forename: Melvin
authors.initials: M
authors.lastname: Zandler
authors.forename: Michael
authors.initials: M
authors.lastname: Van Stipdonk
authors.forename: Dorothy
authors.initials: D
authors.lastname: Hanna
authors.forename: Garold
authors.initials: G
authors.lastname: Gresham
authors.forename: Gary
authors.initials: G
authors.lastname: Groenewold