Stabilization of Pu(IV) in PuBr4(OPCy3)2 and Comparisons with Structurally Similar ThX4(OPR3)2 (R = Cy, Ph) Molecules

Cory J. Windorff, Conrad A. P. Goodwin, Joseph M. Sperling, Thomas E. Albrecht-Schönzart, Zhuanling Bai, William J. Evans, Zachary K. Huffmann, Renaud Jeannin, Brian N. Long, David P. Mills, Todd N. Poe, Joseph W. Ziller

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Abstract

The pursuit of a trivalent plutonium halide phosphine oxide compound, e.g., "PuBr3(OPR)3," instead led to the isolation of the tetravalent trans PuIVBr4(OPCy3)2, PuBr/Cy, compound by spontaneous oxidation of PuIII. Generally, binary PuIV halides are unstable in both solution- and solid-state compounds. The donating nature of phosphine oxides has allowed the isolation and characterization of PuBr/Cy by crystallographic, multi-nuclear NMR, solid state and solution phase UV-vis-NIR spectroscopic techniques. The presence of a putative plutonyl(VI) complex formulated as "trans-PuVIO2Br2(OPCy3)2" was also observed spectroscopically and tentatively observed by single-crystal X-ray diffraction as a co-crystal of PuBr/Cy. A series of transThX4(OPCy3)2 (X = Cl, ThCl/Cy; Br, ThBr/Cy; I, ThI/Cy) complexes were synthesized for comparison to PuBr/Cy. The triphenylphosphine oxide, OPPh3, complexes trans-AnI4(OPPh3)2,
(An = Th, ThI/Ph; U, UI/Ph) were also synthesized for comparison completing the series transUX4(OPPh3)2 (X = Cl, Br, I), UX/Ph. To enable the synthesis of ThI/Cy and ThI/Ph, a new nonaqueous thorium-iodide starting material, ThI4(Et2O)2, was synthesized. The synthesis of organic solvent soluble ThI4L2 (L = Et2O, OPCy3, and OPPh3) are the first examples of crystallographically characterized neutral thorium tetraiodide materials beyond binary ThI4. To show the viability of
ThI4(Et2O)2 as a starting material for organothorium chemistry (C5Me4H)3ThI was synthesized and crystallographically characterized.
Original languageEnglish
JournalInorganic Chemistry
DOIs
Publication statusPublished - 24 Oct 2023

Keywords

  • Plutonium
  • Actinide
  • Tetravalent
  • Octahedral
  • Phosphine oxide

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