Reactions of a bidentate arsine with quadrivalent halides of group IV A. The separation of zirconium and hafnium

Abstract

The ligand o-phenylenebisdimethylarsine (diarsine) reacts with zirconium and hafnium tetrabromides to form new complexes of the type MBr₄,2diarsine which are isostructural with the known complex [TiCl₄,2diarsine]°, a complex in which the titanium atom is eight-co-ordinate with D_2d symmetry. Nine complexes of the early transition elements are therefore now known with this structure. Zirconium tetrachloride reacts immediately in tetrahydrofuran solutions with the diarsine to precipitate the complex [ZrCl₄,2diarsine], but the corresponding reaction of hafnium tetrachloride is much slower. This observation has been developed into a method for the separation of these elements. Reasons for the differing behaviour of the tetrahalides with the diarsine are discussed.

The diarsine also reacts with titanium tetrafluoride and tetraiodide to form complexes of the type (TiF₄)₂,2diarsine and Til₄,2diarsine. The former is believed to be a fluorine-bridged polymer, while the latter can probably be formulated as [Til₂,2diarsine]²⁺ 2l^–.