Hexafluoropentanedionatosilver(I) complexes stabilised by multidentate N-donor ligands: crystal structure of a charge-separated salt species soluble in supercritical carbon dioxide

Abstract

A tetrahydrofuran suspension of silver(I) oxide reacted with Hhfpd (1,1,1,5,5,5-hexafluoropentane-2,4-dione) to give in situ ‘[Ag(hfpd)]’ after removal of the solvent in vacuo. Addition of equimolar ratios of multidentate amines to toluene solutions of the ‘[Ag(hfpd)]’ led to the isolation of several hexafluoropentanedionatosilver(I) complexes, [Ag(hfpd)(L–L)] [L–L = Me ₂ NCH ₂ CH ₂ NHMe (trimen) 1, Me ₂ N(CH ₂ ) ₂ NMe(CH ₂ ) ₂ NMe ₂ (pmdien) 2 or Me ₂ N(CH ₂ ) ₂ NMe(CH ₂ ) ₂ NMe(CH ₂ ) ₂ NMe ₂ (hmten) 3]. Addition of only half a molar equivalent of hmten to a toluene solution of ‘[Ag(hfpd)]’ led to the synthesis of [Ag(hmten)][Ag(hfpd) ₂ ] 4. The products have been characterised by a variety of methods including microanalysis, IR, ¹ H and ¹³ C NMR spectroscopy and mass spectrometry and all complexes dissolve readily in supercritical carbon dioxide. Complexes 2 and 4 have been further characterised by X-ray crystallography. The structure of 2 contains a monomeric five-co-ordinate silver(I) cation in which the two chelating oxygens and two of the three amine nitrogens are in an almost planar arrangement. In comparison, the structure of 4 reveals a charge-separated salt; one of the silver atoms is exclusively co-ordinated to two hfpd ligands in a pseudo-tetrahedral arrangement, whilst the other is encapsulated by an hmten molecule.