Triamidotriazacyclononane Complexes of Group 3 Metals. Synthesis and Crystal Structures

Reaction of yttrium and lanthanide trichlorides (Ln = La, Eu, Yb) with 1 equiv of the trisodium salt of 1,4,7-tris(dimethylsilylaniline)-1,4,7-triazacyclononane (Na3[(SiMe2NPh)3-tacn](THF)2) gives good yields of the compounds
[M{(SiMe2NPh)3-tacn}] (M = Y (1), Eu (3), Yb (4)) and [La{(SiMe2NPh)3-tacn}(THF)] (2). Reduction of 3 with
Na/Hg followed by recrystallization in the presence of diglyme yielded crystals of [Eu{(SiMe2NPh)3-tacn}][Na(diglyme)2] (5). Synthesis of the uranium(III) complex [U{(SiMe2NPh)3-tacn}] (6) is achieved by reaction of 1 equiv
of Na3[(SiMe2NPh)3-tacn](THF)2 with uranium triiodide. The U(IV) complexes, [U{(SiMe2NPh)3-tacn}X] (X = Cl (7);
I (8)), were prepared via oxidation of 6 with benzyl chloride or I2, but salt metathesis from UCl4 provided a higher
yield route for 7. The solid-state structures of 1−7 were determined by single-crystal X-ray diffraction. The ligand
[(SiMe2NPh)3-tacn] generates a trigonal prismatic coordination environment for the metal center in the neutral
complexes 1, 3, 4, and 6 and the ionic 5. In 2 the six nitrogen atoms of the ligand are in a trigonal prismatic
configuration with the oxygen atom of the THF capping one of the triangular faces of the trigonal prism. In 7 the
coordination geometry around the uranium atom is best described as bicapped trigonal bipyramidal.