Novel Cyclopentadienyl-Free Organolanthanides: The First Examples of Five-Membered Amidolanthanide Heterocycles^†

Reactions of LnCl3 (Ln = Nd, Gd, Yb) and [{Me2SiN(R)Li}2] (R = t-Bu, Ph) give the chloride-bridged dimers [{{(t-Bu)NSiMe2SiMe2N(t-Bu)}Ln(μ-Cl)(THF)}2] (1, Ln = Nd; 2, Ln = Gd; 3, Ln = Yb) and [{{(Ph)NSiMe2SiMe2N(Ph)}Ln(μ-Cl)(THF)2}2] (4, Ln = Nd; 5, Ln = Gd; 6, Ln = Yb) in good yields. Compounds 2 and 5 were structurally characterized by X-ray crystallography: 2, triclinic, P1̄, a = 10.321(2) Å, b = 11.116(2) Å, c = 13.434(3) Å, α = 107.57(3)°, β = 111.31(3)°, γ = 90.67(3)°, V = 1356.1(5) Å3, Z = 1, R = 0.0233; 5, monoclinic, P21/n, a = 13.913(13) Å, b = 12.914(9) Å, c = 16.434(14) Å, β = 105.64(3)°, V = 2843(4) Å3, Z = 2, R = 0.0281. The chloro functions in 1−6 remain reactive, demonstrated by the isolation of the trifluoroacetate derivatives of 1 and 2. Treatment of 1 or 2 with 2 equiv of NaOCOCF3 gives [{{(t-Bu)NSiMe2SiMe2N(t-Bu)}Ln(μ-OCOCF3)(THF)}2] (7, Ln = Nd; 8, Ln = Gd). The structure of 8 was determined by a single-crystal X-ray diffraction analysis. Crystal data for 8: triclinic, P1̄, a = 11.045(2) Å, b = 16.120(3) Å, c = 16.949(3) Å, α = 66.17(3)°, β = 85.51(3)°, γ = 78.27(3)°, V = 2702.9(9) Å3, Z = 2, R = 0.0311. The structure of 8 shows the trifluoroacetate group adopting a bridging bidentate mode of coordination.