New lanthanide thioantimonate(V) compounds, [Ln(en)
3(H
2O)
x(
3-x-SbS
4)] (en = ethylenediamine, Ln = La,
x =0,
Ia; Ln = Nd,
x = 1,
Ib) and [Ln(en)
4]SbS
4·0.5en (Ln = Eu,
IIa; Dy,
IIb; Yb,
IIc), were synthesized under mildsolvothermal conditions by reacting Ln
2O
3, Sb, and S in en at 140
C. These compounds were classified as twotypes according to the molecular structures. The crystal structure of type I (
Ia and
Ib) consists of one-dimensionalneutral [Ln(en)
3(H
2O)
x(
3-x-SbS
4)]
(
x = 0 or 1) chains, in which SbS
43- anions act as tridentate or bidentatebridging ligands to interlink [Ln(en)
3]
3+ ions, while the crystal structure of type II (
IIa,
IIb, and
IIc) contains isolated[Ln(en)
4]
3+ cations, tetrahedral SbS
43- anions, and free en molecules. A systematic investigation of the crystalstructures of the five lanthanide compounds, as well as two reported compounds, clarifies the relationship betweenthe molecular structure and the entity of the lanthanide(III) series, such as the stability of the lanthanide(III)-encomplexes, the coordination number, and the ionic radii of the metals.