Protactinium pentachloride structure

Protactinium pentachloride possesses monoclinic symmetry (Table III), but is not isostructurEll with either niobium (138) or uranium pentachloride (127). The structure (67) comprises infinite chains of nonregular... 

Fig. 2. The structure of protactinium pentachloride (67). (a) Portion of the infinite chains in Pads. Coordination of Cl around each Pa is pentagonal bipyra-midal. (b) Bond distances and angles within an isolated PaCl7 group. The four Cl(3) atoms are bridging.

Penta(tropolonato)-protactinium and -uranium have been prepared using tropolone and the metal pentaethoxide in benzene. Uranium pentachloride reacts with an excess of tropolone in non-aqueous solvents to give chlorotetra(tropolonato)uranium. Enthalpies of formation of tri(tropolonato)- and tri(4-methyltropolonato)-aluminium (ill) have been determined at 298.15 K by solution calorimetry. The gas phase enthalpies of formation have been calculated and from these the A1—O bond energies derived. The crystal and molecular structure of a tetranuclear cobalt(ii)-tropolonate complex, [Co4(C7H502)s(H20)2] has been reported. Spectroscopic data (i.r., n.m.r.) of a mercury (ii) tropolonate indicates that it has an unsymmetrical structure with two approximately linear short Hg—O bonds and two longer ones. ... 

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