Complexes of germanium(iv) fluoride with phosphane ligands: structural and spectroscopic authentication of germanium(iv) phosphane complexes

Abstract

The first phosphane complexes of germanium(IV) fluoride, trans-[GeF₄(PR₃)₂] (R = Me or Ph) and cis-[GeF₄(diphosphane)] (diphosphane = R₂P(CH₂)₂PR₂, R = Me, Et, Ph or Cy; o-C₆H₄(PR₂)₂, R = Me or Ph) have been prepared from [GeF₄(MeCN)₂] and the ligands in dry CH₂Cl₂ and characterised by microanalysis, IR, Raman, ¹H, ¹⁹F{¹H} and ³¹P{¹H} NMR spectroscopy. The crystal structures of [GeF₄(diphosphane)] (diphosphane = Ph₂P(CH₂)₂PPh₂ and o-C₆H₄(PMe₂)₂) have been determined and show the expected cis octahedral geometries. In anhydrous CH₂Cl₂ solution the complexes are slowly converted into the corresponding phosphane oxide adducts by dry O₂. The apparently contradictory literature on the reaction of GeCl₄ with phosphanes is clarified. The complexes trans-[GeCl₄(AsR₃)₂] (R = Me or Et) are obtained from GeCl₄ and AsR₃ either without solvent or in CH₂Cl₂, and the structures of trans-[GeCl₄(AsEt₃)₂] and Et₃AsCl₂ determined. Unexpectedly, the complexes of GeF₄ with arsane ligands are very unstable and have not been isolated in a pure state. The behaviour of the germanium(IV) halides towards phosphane and arsane ligands are compared with the corresponding silicon(IV) and tin(IV) systems.