Comparative Zirconium Bromide Cluster Chemistry. A New Structure in K4Zr6Br18C

Abstract

Reactions of ZrBr4, Zr,ABr (A=Li–Cs, Ba), andZ(Be, B, C, Mn) mixtures with suitable compositions in sealed Ta containers have revealed 19 additional examples ofAx(Zr6Br12Z) Bry-type phases that span 0≤y≤6. A new triclinic structure is reported for K4Zr6Br18C (P1,Z=1,a=10.114(2),b=10.283(3),c=10.374(3),α=118.54(2),β=99.98(2),γ=104.08(2),R(F)/Rw=5.1/4.7%) and K4Zr6Br18Fe. Nearly octahedral Zr6(C)Br4−18clusters stack in layers with K+in pseudo-tetrahedral bromine cavities on their outward surfaces. The present structure can be converted to a pseudo-C-centered monoclinic version that is related to those of Rb4Zr6Cl18C (C2/m) and, more distantly, Rb5Zr6Cl18B (Pnam) according to cluster size and the need for good bonding sites for the cations. A variety of other new bromide phases that form in seven known zirconium cluster chloride or iodide structure types according to powder pattern or single crystal data is also reported. Some of these demonstrate greater, lesser, or alternative cation site occupancies in the same basic structure types.