Synthesis and structural diversity of trivalent rare-earth metal diisopropylamide complexes

摘要

A series of rare-earth metal diisopropylamide complexes has been obtained via salt metathesis employing LnCl(3)(THF)(x) and lithium (LDA) or sodium diisopropylamide (NDA) in n-hexane. Reactions with AM : Ln ratios >= 3 gave ate complexes (AM)Ln(NiPr2)(4)(THF)(n) (n = 1, 2; Ln = Sc, Y, La, Lu; AM = Li, Na) in good yields. For smaller rare-earth metal centres such as scandium and lutetium, a Li : Ln ratio = 2.5 accomplished ate-free tris(amido) complexes Ln(NiPr2)(3)(THF). The chloro-bridged dimeric derivatives [Ln(NiPr2)(2)(mu-Cl)-( THF)](2) (Ln = Sc, Y, La, Lu) could be obtained in high yields for Li : Ln = 1.6-2. The product resulting from the Li : La = 1 : 1.6 reaction revealed a crystal structure containing two different molecules in the crystal lattice, [La(NiPr2)(2)(THF)(mu-Cl)](2)center dot La(NiPr2)(3)(THF)(2). Recrystallization of the chloro-bridged dimers led to the formation of the monomeric species Ln(NiPr2)(2)Cl(THF)(2) (Ln = Sc, Lu) and La(NiPr2)(3)(THF)(2). The reaction of YCl3 and LDA with Li : Y = 2 in the absence of THF gave a bimetallic ate complex LiY(NiPr2)(4) with a chain-like structure. For scandium, the equimolar reactions with LDA or NDA yielded crystals of tetrametallic mono(amido) species, {[Sc(NiPr2)Cl-2(THF)](2)(LiCl)}(2) and [Sc(NiPr2)Cl-2(THF)](4), respectively. Depending on the Ln(III) size, AM, and presence of a donor solvent, ate complexes (AM) Ln(NiPr2)(4)(THF) n show distinct dynamic behaviour as revealed by variable temperature NMR spectroscopy. The presence of weak Ln center dot center dot center dot CH(iPr) beta-agostic interactions, as indicated by Ln-N-C angles < 105 degrees, is corroborated by DFT calculations and NBO analysis.