Syntheses and structures of bora-amidinate lanthanide(iii) complexes

Abstract

The use and coordination modes of the dianionic bora-amidinate ligand in lanthanide(III) chemistry is explored. Synthetic routes to complexes of the type ^DIPPNBN-LnR (Ln = lanthanide, ^DIPPNBN = HB[N(2,6-iPr₂-phenyl)]₂, R = an amide or benzylide group) have been developed. The reaction of ^DIPPNBN-H₂ with (DMA)₃Sm (DMA = 2-Me₂N-benzyl) gave dark-red crystals of ^DIPPNBN-Sm(DMA) in 68% yield. The yttrium analogue, ^DIPPNBN-Y(DMA), was prepared similarly (yellow crystals, 58% yield). The reaction of ^DIPPNBN-Sm(DMA) with (Me₃Si)₂NH gave ^DIPPNBN-SmN(SiMe₃)₂·(THF)₂ (yellow crystals, 54% yield). Crystal structure determinations of ^DIPPNBN-Sm(DMA) and ^DIPPNBN-Y(DMA) revealed dimeric complexes that are held together by Ln⋯DIPP interactions. The complex ^DIPPNBN-SmN(SiMe₃)₂·(THF)₂ crystallized as a monomer. NMR investigations of [^DIPPNBN-Y(DMA)]₂ in benzene indicate that it is also dimeric in solution. The addition of THF resulted in its dissociation into monomeric units of ^DIPPNBN-Y(DMA)·(THF)_x.