ZIRCONIUM CHLORIDE CLUSTER PHASES CENTERED BY TRANSITION-METALS MN-NI - EXAMPLES OF THE NB6F15 STRUCTURE

Reactions of Zr, ZrCl4, chlorides of Mn-Ni (Z), and LiCl where appropriate in sealed Ta tubing at 750-900-degrees-C yield the dark purple Li2Zr6Cl15Mn, LiZr6Cl15Fe, Zr6Cl15Co, and Zr6Cl15Ni, all with the basic Nb6F15 structural framework. The structures of all four have been refined by single-crystal X-ray means in the cubic space group Im3BARm, Z = 2. The a dimensions (angstrom) and R and R(W) (%) are, respectively, as follows: Mn, 10.3459 (4), 2.4, 3.4; Fe, 10.2645 (4), 3.3, 4.2; Co, 10.186 (4), 2.4, 2.0; Ni, 10.1907 (4), 2.1, 3.1. Transition-metal-centered clusters in this structure type are interconnected at all vertices by linear chlorine bridges into three-dimensional ReO3-like networks [Zr6(Z)Cl(i)12]Cl(a-a)6/2, and two such networks interpenetrate but are unlinked. The relative sizes of the clusters and bridging halogens are critical for this disposition. The lithium atoms in Li2Zr6Cl12Mn were refined in an internetwork, six-coordinate site of D2h symmetry, consistent with the solid-state NMR spectrum observed for Li-7. The expansions of the networks about Zr-Cl(a-a) necessary to accommodate the lithium ions correspond to volume increments of 12-13 angstrom3 for each ion. The effective sizes of the metal interstitials Z increase slightly from Mn to Ni.