Structural Studies of Rare Earth/Transition Metal Complex Ion Systems as a Basis for Understanding Their Thermal Decomposition to Mixed Oxides
2005; Wiley; Volume: 2005; Issue: 6 Linguagem: Inglês
10.1002/ejic.200400863
ISSN1099-0682
AutoresP.A. Brayshaw, Annegret K. Hall, William T. A. Harrison, Jack M. Harrowfield, Dierdre A. Pearce, Todd M. Shand, Brian W. Skelton, C.R. Whitaker, Allan H. White,
Tópico(s)Radioactive element chemistry and processing
ResumoAbstract Thermal decomposition in air of the series of complexes [Co(NH 3 ) 6 ][Ln(dipic) 3 ] · x H 2 O, [Cr(en) 3 ][Ln(dipic) 3 ] · y H 2 O and [Cr(urea) 6 ][Ln(dipic) 3 ] · z H 2 O (Ln = La – Lu, excluding Pm but plus Y; dipic = 2,6‐pyridinedicarboxylate) to give oxide phases has been examined. The products were characterised by powder X‐ray diffraction, magnetic and surface area measurements. From the Co‐containing species, either Co 3 O 4 + Ln 2 O 3 or perovskite (CoLnO 3 ) products result, while the Cr‐containing species provide CrLnO 4 phases in addition, the monazite form of CrNdO 4 being detected for the first time in this way. Underpinning consideration of the solid state decomposition mechanisms, single‐crystal X‐ray structure de‐terminations have been performed on [Co(NH 3 ) 6 ][Ln(dipic) 3 ] · n H 2 O across the Ln series, defining differing phases (alltriclinic P $\bar {1}$ ) for n = 5 (encompassing Ln = La–Pr), n = 8(.5) (Ln = Tm – Eu) and n = 10 (Ln = Pr – Er, including Y), and also on one of the low‐temperature decomposition products, [Co(NH 3 ) 6 ]Cl · dipic · 2 H 2 O ( 1 ). The structure of 1 provides evidence that conventional π‐stacking of the dipicolinate anions may be of some importance in determining the solid state array, whereas consideration of all structures involving [Ln(dipic) 3 ] 3– anions indicates that “edge‐to‐face” interactions between dipicolinate ligands of adjacent complex anions may also be determinants of the formation of sheet‐like arrays of the trianions commonly observed in these compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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