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

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(N i Pr 2 ) 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(N i Pr 2 ) 3 (THF). The chloro-bridged dimeric derivatives [Ln(N i Pr 2 ) 2 (-Cl)(THF)] 2 (Ln = Sc, Y, La, Lu) could be obtained in high yields for Li:Ln = 1.62. The product resulting from the Li:La = 1:1.6 reaction revealed a crystal structure containing two different molecules in the crystal lattice, [La(N i Pr 2 ) 2 (THF)(-Cl)] 2 La(N i Pr 2 ) 3 (THF) 2 . Recrystallization of the chloro-bridged dimers led to the formation of the monomeric species Ln(N i Pr 2 ) 2 Cl(THF) 2 (Ln = Sc, Lu) and La(N i Pr 2 ) 3 (THF) 2 . The reaction of YCl 3 and LDA with Li:Y = 2 in the absence of THF gave a bimetallic ate complex LiY(N i Pr 2 ) 4 with a chain-like structure. For scandium, the equimolar reactions with LDA or NDA yielded crystals of tetrametallic mono(amido) species, {[Sc(N i Pr 2 )Cl 2 (THF)] 2 (LiCl)} 2 and [Sc(N i Pr 2 )Cl 2 (THF)] 4 , respectively. Depending on the Ln( iii ) size, AM, and presence of a donor solvent, ate complexes (AM)Ln(N i Pr 2 ) 4 (THF) n show distinct dynamic behaviour as revealed by variable temperature NMR spectroscopy. The presence of weak LnCH( i Pr) -agostic interactions, as indicated by LnNC angles