Configurational Trend in the Coordination Arrangement of some Lanthanide(III) Complexes. The Crystal and Molecular Structure of Yb(NCS)3 (THF)4 . Part II.,

The series of lanthanide(III) complexes Ln(NCS)3(THF)4 [Ln = lanthanide(III) ion, THF = tetrahydrofuran] has been synthesized and examined by X-ray diffractometric methods. The study has shown that four oxygen atoms (THF) and three nitrogen atoms (NCS) are arranged around the Ln3+ ions according to well-defined coordination geometries: the square antiprism (SQA) for eight-coordination and the pentagonal bipyramid (PB) for seven-coordination. The dimeric square antiprismatic structures (Ln = Nd, Gd, Eu, Dy and Er) have been previously described. Here we report the crystal structure of Yb(NCS)3(THF)4. The coordination geometry of the metal ion consists of a slightly distorted pentagonal bipyramid, in which two nitrogen atoms (NCS) are in the apical positions and four oxygens atoms (4THF) and one nitrogen (NCS) lie in the equatorial plane. A correlation between the two coordination arrangements (SQA) and (PB) is discussed.