Sterically Demanding Chelating Diamide Complexes of Yttrium and Lutetium

Deprotonation of the bridged diamine ArHN(CH2)3NHAr (Ar = 2,6-iPr2C6H3) with
n-butyllithium and potassium hydride, respectively, gives the corresponding alkali metal
derivatives M2{ArN(CH2)3NAr} (M = Li (1a), K (1b)). 1a reacts with yttrium trichloride to
form the metalate complex [Y{ArN(CH2)3NAr}(THF)2(μ-Cl)2Li(THF)2] (2). The coordination
number of yttrium in 2 is six. The structure of 2 shows two bridging chloride ligands and an
alkali metal bound by two solvate molecules. Further reaction of 2 with NaC5H5 in THF
affords the complex [Y{ArN(CH2)3NAr}(η5-C5H5)(THF)] (4). The structure of 4 in solution
and in the solid state is best described as a distorted tetrahedron. Reaction of 1b with
anhydrous lutetium trichloride leads to the unexpected ionic product [LuCl2(THF)5][Lu{ArN(CH2)3NAr}2] (5). 5 can be formally considered as a derivative of the ionic compound [LuCl2(THF)5][LuCl4(THF)2], in which all four chlorine atoms of the anion are substituted by 2
equiv of the {ArN(CH2)3NAr}2- ligand. As seen from all three structures, the steric demand
of the {ArN(CH2)3NAr}2- ligand is less than that of two (C5Me5)- moieties.