Tantalum complexes chloro

The results of solid state reactions of protactinium dioxide and pentoxide with other metal oxides (89, 93-96) support the view that the oxide systems of protactinium resemble those of other actinide elements rather than those of niobium and tantalum. However, when assessing results of this type one must always bear in mind the relative ionic radii of the respective M " and M + ions since they obviously play a large part in determining the structures of the complex phases. This comment applies equally well, of course, to the structural properties of other types of compound and in particular to the high coordination numbers exhibited by protactinium(V) in its chloro and nitrato complexes. 

Other Halides of Niobium(v) and Tantalum(v). All six of these are yellow to brown or purple-red solids best prepared by direct reaction of the metals with excess of the halogen. The halides melt and boil at 200-300° and are soluble in various organic liquids such as ethers, CC14, etc. They are quickly hydrolyzed by water to the hydrous pentoxides and the hydrohalic acid. The chlorides give clear solutions in concentrated hydrochloric acid, forming oxo chloro complexes. 

CHLORO-COMPLEXES OF PENTAVALENT NIOBIUM, TANTALUM, PROTACTINIUM, TUNGSTEN AND URANIUM,... 

KCl-NaCl-K2TaF7 melts On addition of potassium heptafluotantalate to the NaCl-KCl melt a peak of tantalum reduction to metal (Rl) from fluoro-chloro complex (as will be shown below) was observed on voltammograms (Fig. 1). On the anodic part of the curve several peaks of the deposited tantalum oxidation correspond to it. The anodic peaks OJ andOJ" should be referred to tantalum dissolution respectively in the form of Ta(lV) and Ta(V) chloro complexes, formed in the absence of excess fluoride ions. Recording of the cyclic voltammetric curve with a potential reverse at more positive potential -0.48 or -0.6 V (Fig.l), when the amount of tantalum deposited at the electrode is small and there is not enough time for diffusion of a considerable quantity of the liberated fluorine into the melt bulk, shows no such peaks, which corroborates our assumption. Peaks Oi and OJ were caused by tantalum disso-... 

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