Lanthanide Complexes of Boraamidinate Ligands: Synthesis and X-ray Structures of {[Li(THF)<sub>4</sub>][<i>bam</i>LnCl<sub>2</sub>(THF)]}<sub>2</sub> (<i>bam</i> = [PhB(NDipp)<sub>2</sub>]<sup>2−</sup>; Ln = Y, Pr, Nd, Sm, Ho, Er, Yb) and {<i>bam</i>LnCl(THF)<sub>2</sub>}<sub>2</sub> (Ln = Y, Sm)
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The first examples of the incorporation of the boraamidinate ligand into lanthanide complexes have been prepared by reaction of equimolar amounts of [Li2][PhB(NDipp)2] and LnCl3 in tetrahydrofuran (THF), which produces “ate” complexes of the form {[Li(THF)4][bamLnCl2(THF)]}2 [Ln = Y (9a), Pr (9b), Nd (9c), Sm (9d), Ho (9e), Er (9f), Yb (9g)] through the inclusion of the LiCl by-product. The isostructural complexes 9a−g were characterized in the solid state by X-ray crystallography, which revealed ion-separated complexes composed of a dimeric anion with a terminal and a bridging chloride ligand on each metal center and a tetrasolvated cation, [Li(THF)4]+. In solution, the yttrium complex 9a was characterized by multinuclear (1H, 13C, 7Li, and 11B) NMR spectroscopy. The 1H and 7Li NMR spectra of the paramagnetic complexes 9b−9d showed broad resonances, but NMR spectra could not be obtained for 9e−g. The complexes 9a−g are readily soluble in THF, but insoluble in diethyl ether and hexane. The reaction of {[Li(THF)4][bamLnCl2(THF)]}2 (Ln = Y, Sm) with an excess of trimethysilyl trifluoromethanesulfonate (TMSOTf) generates the dimeric neutral complexes {bamLnCl(THF)2}2, which have been characterized by 1H NMR and X-ray crystallography.
