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Journal of the Chemical Society A: Inorganic, Physical, Theoretical


Journal of the Chemical Society A: Inorganic, Physical, Theoretical was published from 1966 - 1971.

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Paper

J. Chem. Soc. A, 1971, 81 - 87, DOI: 10.1039/J19710000081

Halogeno-, oxohalogeno-, and ethoxyhalogeno-complexes of quinquevalent protactinium, uranium, niobium, and tantalum

D. Brown and C. E. F. Rickard

Metal penta-chlorides and -bromides react with tetraethylammonium chloride or triphenylphosphine oxide (tppo) in anhydrous ethanol to yield ethoxyhalogeno-complexes of the types NEt4[M(OEt)2X4] and M(OEt)2X3,(tppo), respectively (M = Pa, Nb, or Ta; X = Cl or Br). In the presence of an excess of tetraethylammonium chloride reactions involving niobium(V), but not those involving protactinium(V) or tantalum(V), result directly in the formation of oxopentahalogeno-complexes, [NEt4]2[NbOX5]. Analogous protactinium(V) complexes and [PaOCl3-(tppo)2] and [PaOBr3(tppo)2] crystallise when the appropriate ethoxy-complex and either tetraethylammonium chloride or triphenylphosphine oxide are heated with methyl cyanide containing ca. 0·5% water. These are the first examples of complexes containing the PaO group. Pentahalide complexes of the type [MX5(tppo)2](M = Pa and U) are obtained from reactions in anhydrous methyl cyanide or methylene dichloride. Some chemical properties, conductivity studies, and i.r. spectral and X-ray diffraction results are reported.