Lanthanide Complexes of Boraamidinate Ligands: Synthesis and X-ray Structures of {[Li(THF)4][bamLnCl2(THF)]}2 (bam = [PhB(NDipp)2]2−; Ln = Y, Pr, Nd, Sm, Ho, Er, Yb) and {bamLnCl(THF)2}2 (Ln = Y, Sm)

Abstract

The first examples of the incorporation of the boraamidinate ligand into lanthanide complexes have been prepared by reaction of equimolar amounts of [Li(2)][PhB(NDipp)(2)] and LnCl(3) in tetrahydrofuran (THF), which produces "ate" complexes of the form {[Li(THF)(4)][bamLnCl(2)(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 ((1)H, (13)C, (7)Li, and (11)B) NMR spectroscopy. The (1)H and (7)Li 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)][bamLnCl(2)(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 (1)H NMR and X-ray crystallography.