Z. Naturforsch. **2013**,
*68b*, 616 – 624

doi:10.5560/ZNB.2013-3083

Syntheses and Crystal Structures of the Bromide-derivatized Lanthanoid(III) Ortho-Oxomolybdates(VI) *Ln*Br[MoO_{4}] (*Ln* = Pr, Nd, Sm, Gd–Lu)

Tanja
Schustereit,
Harald
Henning,
Thomas
Schleid, and
Ingo
Hartenbach

University of Stuttgart, Institute for Inorganic Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany

Received February 20, 2013 / published online Juli 2, 2013

Dedicated to Professor Heinrich Nöth on the occasion of his 85^{th} birthday

The lanthanoid(III) bromide ortho-oxomolybdates(VI) *Ln*Br[MoO_{4}] (*Ln* = Pr, Nd, Sm, Gd–Lu) crystallize triclinically in the space group *P*1̅ (*a* = 686–689, *b* = 713–741, *c* = 1066–1121 pm, *α* = 103–106, *β* = 107–108, *γ* = 92–95°) with *Z* = 4. The crystal structure contains two crystallographically distinguishable *Ln*^{3+} cations, each one with a coordination number of seven *plus* one. (*Ln*1)^{3+} is surrounded by three bromide and four *plus* one oxide anions, while for
(*Ln*2)^{3+} just one bromide and six *plus* one oxide anions belong to the coordination sphere. Considering the smallest lanthanoids, however, the distances to the farthest anions increase so much that their contribution to the coordination spheres becomes negligible in both cases. The polyhedra around (*Ln*1)^{3+} are connected to each other *via* common edges, which consist of two crystallographically identical Br^{−} anions (Br1). Furthermore, the common structure of the *Ln*Br[MoO_{4}] series contains two crystallographically different, discrete [MoO_{4}]^{2−} ortho-oxomolybdate(VI) tetrahedra. Two *plus *one oxygen atoms of each [(Mo1)O_{4}]^{2−} unit are used to interconnect the polyhedra around (*Ln*1)^{3+} and (*Ln*2)^{3+} together with one Br^{−} anion (Br2). The connection between two polyhedra around (*Ln*2)^{3+} is generated exclusively by two *plus* one oxygen atoms of two [(Mo2)O_{4}]^{2−} anions. The complete structural arrangement can be considered as a bundle of primitively packed _{∞}^{1}{*Ln*Br[MoO_{4}]} chains with two alternating motifs of linkage, which are running parallel along [012].

*Key words:* Lanthanoids, Bromides, Oxomolybdates, Crystal Structure