Preparation and properties of halogeno-, oxyhalogeno-, and ethoxyhalogeno-complexes of uranium(V)

Abstract

Hexahalogenouranates(V), [M][UX₆][M = N(C₂H₅)₄ or As(C₆H₅)₄; X = Cl or Br]. and pentahalide–tppo complexes, UX₅·tppo (X = Cl or Br; tppo = triphenylphosphine oxide), react with anhydrous oxygen-free ethanol at room temperature to yield new complexes of the types [M][U(OC₂H₅)₂X₄] and U(OC₂H₅)₂X₃˙tppo, respectively. Controlled hydrolysis of [N(C₂H₅)₄][U(OC₂H₅)₂Cl₄] and interaction of [N(C₂H₅)₄][UCl₆] and As₂O₃ in non-aqueous solvents containing [N(C₂H₅)₄]Cl provide new routes to [N(C₂H₅)₄]₂[UOCl₅], which crystallises in the monoclinic space group Cc with a= 14.20(1), b= 14.36(1), c= 13.29(1)Å, and β= 90.25(3)°. Oxygen-18 substitution studies have been undertaken in order to facilitate assignment of the vibrational spectrum of this compound. Infrared and electronic spectral data are also reported for the ethoxyhalogeno-complexes and for the previously uncharacterised fluoro-complexes [N(C₂H₅)₄][UF₆] and [N(C₂H₅)₄]₂[UF₇]. Attempts to obtain oxychloro-complexes of the type UOX₃·2tppo by controlled hydrolysis of the appropriate ethoxy-complex or by reactions involving UX₅·tppo and As₂O₃ have resulted in disproportionation of U^V to U^IV and U^VI.