Structural Studies of Rare Earth/Transition Metal Complex Ion Systems as a Basis for Understanding Their Thermal Decomposition to Mixed Oxides

Authors:
Publisher website
Google Scholar
Abstract
Thermal decomposition in air of the series of complexes [Co(NH3)6][Ln(dipic)3]·x H2O, [Cr(en)3][Ln(dipic)3]·y H2O and [Cr(urea)6][Ln(dipic)3]·z H2O (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 Co3O4 + Ln2O3 or perovskite (CoLnO3) products result, while the Cr‐containing species provide CrLnO4 phases in addition, the monazite form of CrNdO4 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(NH3)6][Ln(dipic)3]·n H2O 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(NH3)6]Cl·dipic·2 H2O (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)

This publication has 61 references indexed in Scilit: