Zirconium atom, structural features

The only crystalline phase which has been isolated has the formula Pu2(OH)2(SO )3(HaO). The appearance of this phase is quite remarkable because under similar conditions the other actinides which have been examined form phases of different composition (M(OH)2SOit, M=Th,U,Np). Thus, plutonium apparently lies at that point in the actinide series where the actinide contraction influences the chemistry such that elements in identical oxidation states will behave differently. The chemistry of plutonium in this system resembles that of zirconium and hafnium more than that of the lighter tetravalent actinides. Structural studies do reveal a common feature among the various hydroxysulfate compounds, however, i.e., the existence of double hydroxide bridges between metal atoms. This structural feature persists from zirconium through plutonium for compounds of stoichiometry M(OH)2SOit to M2 (OH) 2 (S0O 3 (H20) i,. Spectroscopic studies show similarities between Pu2 (OH) 2 (SOO 3 (H20) i, and the Pu(IV) polymer and suggest that common structural features may be present. 

Crystals of complex 112 suitable for an X-ray structure determination were obtained on cooling a solution in pentane to — 30 °C. The structure determined is shown in Fig. 7.9. The most remarkable structural feature of 112 is that the gallium center is connected to the zirconium through two different c-carboxylic bridges. One of them contains the cyclo-C6Hg system, which is t]1-bonded to gallium and r 2-coordinated to zirconium. It is noteworthy that carbon atom C-2 is planar tetracoordinate. It is connected to four neighboring atoms in the c-plane, specifically to carbon atoms C-l and C-3 and to both metal centers [175]. 

ZrCl has a homoatomic-layer structure sequenced Cl-Zr-Zr-Cl. Each Zr atom has three neighbours in the adjacent sheet at 3.09 A, six more in the same sheet at 3.42 A and three chlorine atoms on the other side at 2.63 A. Weak chlorine-chlorine interactions between sheets at 3.61 A contrast with the strong metal-metal binding within sheets. These structural features account for the graphitic nature and anisotropic electrical conduction of ZrS. Thermodynamic parameters have been obtained for the reduction of zirconium chlorides. The reaction of ZrC with a melt containing alkali-metal chlorides and titanium chlorides has been investigated. ... 

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