Abstract Spectroscopically pure PaPc2 has been prepared by reaction between PaI4 · 4 CH3CN and o-phthalic acid dinitrile in 1-chloronaphthalene followed by sublimation at 5 · 10-3 Pa in a temperature profile with three clearly defined zones (520 °C/350 °C/room temperature). This procedure gives a product almost completely free of H2Pc impurity which is known to have been present in previously reported complexes of the type AnPc2. Thus, the trace of H2Pc in the substance could only be detected by derivative spectroscopy. X-ray powder diffraction shows the compound to be isostructural with ThPc2 and UPc2. The ligand spectrum is typical of AnPc2 complexes, f-f Bands observed in a solid state spectrum provide additional proof that the compound is PaIV Pc2.
The preparation of protactinium metal by a modified van Arkel technique is described. The product exhibits the body-centred tetragonal structure with a, = 3.931 (1) and c, = 3.236(1) 8. Conditions for conversion of the metal into the tetra-and penta-halides (Pax,, X = CI or Br; Pax,, X = F, CI, Br, or I) by reactions involving a variety of halogenating agents are described. Reaction with gaseous hydrogen yields either a-PaH, (250 "C) or P-PaH, (400 "C) which are isostructural with their uranium analogues. The stability of the metal on exposure to the atmosphere has been confirmed. SMALL quantities of protactinium metal were apparently first obtained by Grosse and Agruss in 1934 by bombarding Pa,O, with 35-keV electrons in a high vacuum and by decomposition of pentahalides on a hot filament.? Neither product was identified with certainty. Subsequently, milligram amounts were obtained by reduction of protactinium tetrafluoride with barium vapour at 1 300-1 400 "C using the double-crucible technique with tantalum crucibles. A refinement of this procedure involved a BaF, crucible suspended inside t Throughout this paper: 1 eV x 1.60 x
Die siebenfach‐koordinierte, pentagonal‐bipyramidale Titelverbindung wird erhalten durch Reaktion von U02C12 , mit KNCS und Triphenylphosphinoxid in Aceton‐Methanol‐Mischung bzw. durch Behandlung von UO2(NCS)2(PPh3O), mit Aceton bei Raumtemperatur.
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