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.