Crystallochemistry of some new niobium bromides with (Nb6Br18) units: Structures of CsErNb6Br18 and Cs2EuNb6Br18

Abstract Two new series of Nb 6 bromides, CsRENb 6 Br 18 (RE = all the lanthanides excepted Eu and Yb, + Y) (type H ) and M 2 RENb 6 Br 18 (M = Cs, Rb, Tl; RE = Eu, Yb) (type R ) have been isolated. The crystal structures of CsErNb 6 Br 18 and Cs 2 EuNb 6 Br 18 , isotypic with the corresponding chlorides, have been determined by single crystal X‐ray diffraction data. The (Nb 6 Br 18 ) intra‐unit strength is related to the nature and the charge of the counter cation. A comparison between the corresponding chlorides and bromides series, based on the chemical properties and the size of the halogen is discussed.