NMR spectroscopic study of adduct formation of neptunium(IV). beta. -diketonates

Neptunium(IV) pivaloyltrifluoroacetonate Np(PTFA)/sub 4/, its adduct with trimethylphosphine oxide (TMPO), neptunium(IV) hexafluoroacetylacetonate Np(HFA)/sub 4/, and its adducts with TMPO and trimethyl phosphate (TMP) were synthesized. It was shown by NMR spectroscopy that adducts of Np(PTFA)/sub 4/ with TMPO and Np(HFA)/sub 4/ with TMP have a 1:1 composition; moreover, there is no coordination of subsequent molecules of the neutral ligand when it is present in excess. In the system Np(HFA)/sub 4/=TMPO, on the contrary, the formation of 1:1, 1:2, and 1:3 adducts is observed; moreover, in the last two cases there is an opening of the chelate rings with maintenance of a coordination number of 9 for neptunium. Thus, the ability of NP(IV) ..beta..-diketonates for adduct formation increases sharply as the basicity of the ..beta..-diketonates anion is weakened (the previously studied perfluorinated chelate - neptunium(IV)dipivaloylmethanate - does not form adducts at all).