Synthesis, characterisation and alkylation reactions of lanthanide β-diketiminates; crystal structures of [Nd(L–L)2Cl] and [Ce(L–L)(CHR2)2] [L–L = N(R)C(Ph)C(H)C(Ph)NR, R = SiMe3]

Abstract

Treatment of two equivalents of the sodium β-diketiminate Na(L–L) 1 with a lanthanide metal(III) chloride, LnCl ₃ , yielded the mononuclear complex [Ln(L–L) ₂ Cl] (Ln = Ce 3, Pr, Nd 5, Sm or Yb); similarly, two equivalents of 1 with TmI ₃ gave [Tm(L–L) ₂ I] [L–L = N(R)C(Ph)C(H)C(Ph)NR; R = SiMe ₃ ]. When 3 was mixed with either one or two equivalents of Li(CHR ₂ ) in diethyl ether, the only new cerium-contaning product was [Ce(L–L)(CHR ₂ ) ₂ ] 9. Lanthanide metal(III) β-diketiminates [Ln(L–L) ₂ (thf) ₂ ] (Ln = Sm or Yb) or [Yb(L–L) ₂ ] and [Yb(L–L′) ₂ ] 13 were obtained from [LnI ₂ (thf) ₂ ] (Ln = Sm or Yb) and K(L–L) in thf, or YbI ₂ and K(L–L) or K(L–L′) in Et ₂ O [L–L′ = N(R)C(Ph)C(H)C(Bu ^t )NR; thf = tetrahydrofuran]. The various lanthanide metal β-diketiminates were characterised by elemental analysis, mass spectrometry and multinuclear NMR spectra. The last of these indicated (by variable-temperature experiments) that for [Yb(L–L′) ₂ ] 13 two isomers were present. X-Ray diffraction data for [NdL–L) ₂ Cl] 5 and [Ce(L–L)(CHR ₂ ) ₂ ] 9 revealed that for each of these crystalline mononuclear complexes the metal atom is well shielded, due to the extremely sterically demanding monoanionic [L–L] ^- ligand, which has some η ⁵ character in these molecules.