Complexes of Triamidoamines with the Early Actinides. Synthetic Routes to Monomeric Compounds of Tetravalent Uranium and Thorium Containing Halide and Amide Ligands.

The reaction of the lithiated triamidoamine [Li3(NN‘3)(THF)3] [NN‘3 = N(CH2CH2NSiMe2But)3] with AnCl4 (An = U, Th) followed by sublimation gives monomeric [An(NN‘3)Cl]. Reaction of these complexes with SiMe3X (X = Br, I) gives [An(NN‘3)X]. The amido derivatives [An(NN‘3)(NEt2)] are prepared from H3(NN‘3) and [U(NEt2)4] and from [Th(NN‘3)Cl] and [Li(NEt2)]. In each case, the complexes [U(NN‘3)X] (X = Cl, Br, I, NEt2) are shown by X-ray crystallography to contain a triamidoamine ligand disposed with 3-fold symmetry about the metal center. The structures are distorted from trigonal bipyramidal by displacement of the uranium atoms out of the equatorial plane of the three amido nitrogen atoms by ca. 0.8 A. The ligand backbone is distorted in such a manner as to cause the tert-butyldimethylsilyl groups to encircle the equatorial plane of the metal atom rather than surround the apical coordination site as is observed in the transition metal complexes of this type. Variation of the auxiliary ligand has little eff...