SYNTHESIS AND STRUCTURE OF THE CENTERED CLUSTER COMPOUND BA3(ZR6CL18BE)

Reaction of powdered Zr with ZrCl4, BaCl2 and Be in suitable proportions in a Ta container at 800-degrees-C produces the title compound. Suitable monocrystals for X-ray diffraction were obtained from reactions to which a comparable amount of Hg2Cl2 had been added. The structure of Ba3Zr6Cl18Be is a superstructure of the K2ZrCl6.Zr6Cl18H type (R3cBAR, Z = 6; a = 9.6852 (9) angstrom, c = 52.52 (1) angstrom; R, R(w) = 2.7, 3.2 % for 826 independent reflections, 2-theta less-than-or-equal-to 50-degrees). Trigonally compressed [Zr6(Be)Cl12i]Cl6a clusters are interconnected by six-coordinate barium atoms that lie in Cl(a) antiprisms (a twisted version of the Zr(IV) site) while (9 + 3)-coordinate barium substitutes for potassium within chlorine layers. Distortions associated with the size and field of barium are responsible for the superstructure and for differences from other analogues.