Solvothermal syntheses and characterizations of lanthanide(iii)/SbS43− complexes associated by a dien ligand: A detailed study based on the lanthanide contraction effect

Abstract

Neutral lanthanide thioantimonate complexes with the formula [Ln(dien)₂(μ-η¹, η²-SbS₄)]_n (Ln1) (Ln = Pr 1a, Nd 1b, Sm 1c) and [Ln(dien)₂(η²-SbS₄)] (Ln2) (Ln = Eu 2a, Dy 2b) have been synthesized by the solvothermal reaction of antimony and sulfur powders with the corresponding lanthanide oxide in diethylenetriamine (dien). In 1a–1c, the tetrathioantimonate SbS₄³⁻ anion acts as a μ-η¹, η²-SbS₄ tridentate bridging ligand to interlink [Ln(dien)₂]³⁺ ions into neutral 1D coordination polymers [Ln(dien)₂(μ-η¹, η²-SbS₄)]_n, but it coordinates to the Ln³⁺ ions of [Ln(dien)₂]³⁺ in 2a and 2b as a η²-SbS₄ bidentate chelating ligand, leading to neutral complexes [Ln(dien)₂(η²-SbS₄)]. The Ln³⁺ ions are in 9-fold and 8-fold coordinations in Ln1 and Ln2 respectively. A systematic investigation of the crystal structures of five complexes as well as two reported compounds revealed that the soft Lewis basic ligand SbS₄³⁻ coordinates to the larger lanthanide ions La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, and Sm³⁺ as a μ-η¹, η²-SbS₄ tridentate bridging ligand, and to the smaller lanthanide ions Eu³⁺ and Dy³⁺ as a η²-SbS₄ bidentate chelating ligand, which exhibits a lanthanide contraction effect on the coordination mode of the SbS₄³⁻ ligand to the Ln³⁺ centers.