Encapsulation of the transition metals chromium through cobalt in zirconium cluster iodides
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The phases Zr6I12Cr, Zr6I12Mn, Zr6I14Fe, Zr6I14Co, CsZr6I14Mn, Cs0.63Zr6I14Fe, and CsxZr6I14Co have been synthesized by reaction of Zr, Zrl4, the appropriate transition-metal diiodide, and cesium iodide where appropriate at 750850 C in sealed tantalum containers. They have the structural frameworks of Zr6I12C (space group R3) or CsZr6I14C (Cmca) but with the transition metal interstitial instead of carbon centered in the expanded zirconium octahedra. The structures of CsZr6I14Mn and Cs0.63Zr6I14Fe were established by single-crystal X-ray diffraction methods. The zirconium-interstitial distances in the relatively large clusters are short compared with other examples, averaging 2.490 and 2.484 , respectively. Extended Hckel calculations for Zr6I14Fe highlight the differences between transition-metal and main-group interstitial elements, the former exhibiting a preferred stability at 18 rather than 14 cluster-binding electrons through the addition of the nonbonding eg4 level on the interstitial. The iron-zirconium bonding in the cluster is notably greater than that in Zr3Fe. The phase CsZr6I14Mn is properly diamagnetic, while the magnetic susceptibility data for the 19-electron Zr6I12Mn are well described by a high-temperature eff of 1.84 B and an intracluster spin-orbit coupling ( = 312 cm1) that partially quenches the moment at lower temperatures. 1988, American Chemical Society. All rights reserved.