Synthesis, characterization, and reactivity of a uranyl(V) diketiminate complex


Trevor W. Hayton and Guang Wu. Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA 93106
The uranyl(V) cation is generated upon photolysis of uranyl(VI) in the presence of alcohols and is implicated as an intermediate in the uranyl catalyzed photo-oxidation of alkanes. The uranyl(V) cation is known to undergo a facile disproportionation to uranyl(VI) and U(IV), probably via an oxo-bridged transition state. To prevent this disproportionation we have ligated uranyl(VI) to a bulky beta-diketiminate and explored the reduction chemistry of this complex. Thus, reaction of Li[Ar2nacnac] (Ar = 2,6-(iPr)2C6H3) with UO2Cl2(THF)3 provides [UO2(Ar2nacnac)Cl]2 (I) in high yield. Complex I has proven to be a useful starting material, as it reacts with many Lewis bases and its chloride ligands readily undergo metathesis. For instance, addition of Ph3PO to I provides UO2(Ar2nacnac)(OPPh3)Cl, while reaction of I with AgOTf in the presence DPPMO2 (DPPMO2 = (Ph2P=O)2CH2) or Ph2MePO generates [UO2(Ar2nacnac)(DPPMO2)][OTf] (II) and [UO2(Ar2nacnac)(Ph2MePO)2][OTf] (III) respectively. Reduction of II with Cp2Co surprisingly generates a new uranyl(VI) complex, UO2(Ar2nacnac)(CH{Ph2PO}2), which is formed by the formal loss of H from the DPPMO2 ligand. In contrast, reduction of III with Cp2Co provides the anticipated uranyl(V) complex, namely UVO2(Ar2nacnac)(Ph2MePO)2, in good yields. Characterization and preliminary reactivity studies of this new uranyl(V) complex will be discussed.

General Inorganic Chemistry
9:00 AM-1:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 219, Oral

Division of Inorganic Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008