Linear Trimeric Hafnium Clusters in Hf 0
The reduction of hafnium tetraiodide, HfI4, with aluminum at 600 °C or 850 °C in the presence of a NaI flux resulted in black single crystals of Hf0.86(1)I3. This composition corresponds well to the upper end of the non-stoichiometry range 0.89 ≤ x ≤ 1.00 previously reported for HfxI3. The crystal structure (a = 1250.3(2), c = 1999.6(3) pm, R-3m, Z = 18) is made up of hexagonal closest packed layers of iodide ions. One third of the octahedral holes would be filled as in TiI3 or ZrI3 if it were Hf1.00I3. In Hf0.86(1)I3, one out of six octahedral holes along [001] are, however, only occupied by 16%. In contrast to TiI3-I and ZrI3, one striking structural feature is in the formation of linear hafnium trimers with identical Hf―Hf distances of 318.3(2) pm rather than the formation of dimers. These may be associated with Hf―Hf bonding although only 2.64 electrons are available for one Hf5.16I18 column.
Magnetochemische Untersuchungen XLIX. Das magnetische Verhalten der Titantrihalogenide
TiCl3 zeigt bei tiefen Temperaturen Antiferromagnetismus; bei etwa –60°findet sich eine starke Zunahme der Suszeptibilitat. Diese ubersteigt bei hoher Temperatur den Wert, der sich fur freie Tia3+-Ionen berechnet. Es wird geschlossen, das bei hohen Temperaturen die Ti3+-Ionen in Tie2+-und Ti4+-Ionen disproportionieren.
Synthesis by hydrogen-driven disproportionation reactions. Synthesis and structure of the hexazirconium dodecahalide clusters Zr6Cl12 and Zr6Br12 and the double salt Zr6Cl12.M2ZrCl6 (M = sodium, potassium, cesium)
The ZrXH phases, X = Cr, Br, formed by reaction of H/sub 2/ with double-metal-layered ZrX at 150 to 450/sup 0/ are metastable and decompose at 630 to 780/sup 0/C to ZrH/sub 2/ plus the cluster compound Zr/sub 6/H/sub 12/, the latter being isostructural with Zr/sub 6/I/sub 12/. Transport of Zr/sub 6/Cl/sub 12/ occurs in the sealed Ta container at about 800/sup 0/C. The two cluster phases are also formed as powders from incomplete reactions of ZrX and ZrX/sub 4/ at 650 to 700/sup 0/C, while the layered 3R-ZrCl/sub 2/ is more stable at lower temperatures. Decomposition of ZrClH in the presence of NaCl, or CsCl at 750/sup 0/C yields the isostructural M/sub 2/Zr/sub 7/Cl/sub 18/ (M = Na, K, Cs) while ZrCl does not react with NaCl or KCl alone under the same conditions. The crystal structure of the double salt K/sub 2/Zr/sub 7/Cl/sub 18/ was solved by single-crystal diffractometer methods (R anti 3, a = 9.499 (2) A, c = 25.880 (6) A, R = 0.037, R/sub w/ = 0.049, 736 Mo K..cap alpha.. diffractions corrected for absorption). The structure contains the octahedral metal cluster Zr/sub 6/Cl/sub 12/ slightly compressed along the anti 3 axis (d(Zr-Zr) = 3.224more » (1), 3.178 (1) A) and edge bridged by chlorine. Halides in octahedral ZrCl/sub 6//sup 2 -/ groups occupy all exo positions of the clusters. The structure can also be described in terms of nine chlorine layers per cell containing regular potassium and vacancy substitutions together with zirconium (II) and zirconium (IV) in octahedral interstices. The Zr/sub 6/Cl/sub 12/ and Na/sub 2/Zr/sub 7/Cl/sub 18/ phases quenched in the presence of hydrogen at approx. 1 atm do not contain hydrogen in the clusters.« less