title: Expanding the Chemistry of Molecular U(2+) Complexes: Synthesis, Characterization, and Reactivity of the {[C5 H3 (SiMe3 )2 ]3 U}(-) Anion.
abstract: The synthesis of new molecular complexes of U(2+) has been pursued to make comparisons in structure, physical properties, and reactivity with the first U(2+) complex, [K(2.2.2-cryptand)][Cp'3 U], 1 (Cp'=C5 H4 SiMe3 ). Reduction of Cp''3 U [Cp''=C5 H3 (SiMe3 )2 ] with KC8 in the presence of 2.2.2-cryptand or 18-crown-6 generates [K(2.2.2-cryptand)][Cp''3 U], 2-K(crypt), or [K(18-crown-6)(THF)2 ][Cp''3 U], 2-K(18c6), respectively. The UV/Vis spectra of 2-K and 1 are similar, and they are much more intense than those of U(3+) analogues. Variable temperature magnetic susceptibility data for 1 and 2-K(crypt) reveal lower room temperature χM T values relative to the experimental values for the 5f(3) U(3+) precursors. Stability studies monitored by UV/Vis spectroscopy show that 2-K(crypt) and 2-K(18c6) have t1/2 values of 20 and 15 h at room temperature, respectively, vs. 1.5 h for 1. Complex 2-K(18c6) reacts with H2 or PhSiH3 to form the uranium hydride, [K(18-crown-6)(THF)2 ][Cp''3 UH], 3. Complexes 1 and 2-K(18c6) both reduce cyclooctatetraene to form uranocene, (C8 H8 )2 U, as well as the U(3+) byproducts [K(2.2.2-cryptand)][Cp'4 U], 4, and Cp''3 U, respectively.
authors.affiliation: Department of Chemistry, University of California-Irvine, Irvine, CA 92697 (USA).
authors.forename: Cory J
authors.initials: CJ
authors.lastname: Windorff
authors.affiliation: Department of Chemistry, University of California-Irvine, Irvine, CA 92697 (USA).
authors.forename: Matthew R
authors.initials: MR
authors.lastname: MacDonald
authors.affiliation: Department of Chemistry, University of California-Berkeley, Berkeley, CA 94720 (USA).
authors.forename: Katie R
authors.initials: KR
authors.lastname: Meihaus
authors.affiliation: Department of Chemistry, University of California-Irvine, Irvine, CA 92697 (USA).
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Ziller
authors.affiliation: Department of Chemistry, University of California-Berkeley, Berkeley, CA 94720 (USA). jrlong@berkeley.edu.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Long
authors.affiliation: Department of Chemistry, University of California-Irvine, Irvine, CA 92697 (USA). wevans@uci.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Evans
keywords: cyclopentadienyl ligands; hydrides; oxidation states; reduction; uranium