Complexes of the lanthanides with hexamethylphosphoramide

Abstract

COMPLEXES OF THE LANTHANIDES WITH HEXAMETHYLPHOSPHORAMIDE Martin T. Durney and Robert S. Marianelli Chemistry Department University of Nebraska Lincoln, Nebraska 68508 ~ e c e i v e d 17 July 1970) It has been recently reported by DONOGHUE et al (i) and by GIESBRECHT and ZINNER (2) that the Lanthanides (Ln) form cationic complexes with hexamethylphosphoramide (~PA), 0 = P(N(CH3)2) 3, of the type Ln(CIO4)~ 6 HMPA. It was concluded by DONOGHUE et el, on the basis of analytical, infrared (i.r.) and conductivity data that the complexes were hexacoordinated with six bonded HMPA ligands and therefore should be written as [Ln(HMPA)6][CI04] 3. In an attempt to prepare some of these complexes following DONOGHUE'S method (i), we repeatedly obtained a product whose analyses were not in agreement with the reported stoichiometry. For Ln = La, Gd and Dy, light tancolored precipitates a were obtained which darkened noticeably on standing in a desiccator in the light. Analyses of these products did not agree with any reasonable stoichiometric assignment for the complex. GIESBRECHT and ZINNER's procedure (2) also did not yield the reported complexes. We wish to report the preparation and characterization of a series of stable, perchlorate-bonded lanthanide complexes of the type [Ln(HMPA)4(OCI03)2] [CIO4] , (Ln = La, Nd, Gd, Dy and Yb). Experimental Preparation of Complexes The corresponding Ln203 was dissolved in an excess of concentrated perchloric acid (~3M). The resulting solution was adjusted to pH 4-5 with potassium hydroxide. The potassium perchlorate was filtered and the filtrate was evaporated to dryness at reduced pressure (~20 mm). The hydrated perchlorate was then dissolved in absolute ethanol and this