Lanthanide metal amides revisited; the use of the 2,2,6,6-tetramethylpiperidinato (TMP) ligand

Abstract

Group 3 (Y) and 4f (largely Ce) metal(III) amides (largely 2,2,6,6-tetramethylpiperidinates) have been prepared and structurally characterised: [Y(TMP)₃] (1), [Ce(TMP)₃(thf)] (2), [Li(thf)₄][CeBr(TMP)₃] (3), [{Y(TMP)₂(μ-OEt)}₂] (4), [{Y(TMP)₂}₂(μ-OEt)(μ-OBuⁿ)] (5), [{Ce(TMP)₂(μ-OEt)}₂] (6) and [LaBr{N(SiMe₃)(C₆H₃Prⁱ₂-2,6)}₂(thf)] (10) [TMP = NC(Me)₂(CH₂)₃C(Me)₂]. Low yields of crystalline TeCl(TMP) (7) and [CeCl₂(thf)₅][TeCl₅(thf)] (9) were obtained from unsuccessful attempts to oxidise compound 2 by treatment with TeCl₄. The compound Br(TMP) (8), obtained from H(TMP) and N-bromosuccinimide, failed to react with tellurium. The X-ray structures of 1–7, 9 and 10 are reported. Such data for the TMP derivates 1–7 and 9 show significant differences from those of N(SiMe₃)₂ analogues, largely because the TMP ligand is sterically more demanding.