Synthesis and characterisation of bis(diphenylphosphino)-amine complexes of platinum(II)

Abstract

The complexes [PtCl(PR₃)(dppa)]Cl (PR₃= PMe₃, PMe₂Ph, PMePh₂, PBuⁿ₃, PPh₃ or PEt₃) have been prepared by the reaction of bis(diphenylphosphino)amine, dppa(Ph₂PNHPPh₂), with cis-[PtCl₂(PR₃)₂] in CH₂Cl₂. With [PtCl₂(dppe)](dppe = Ph₂PCH₂CH₂PPh₂), [Pt(dppe)(dppa)]Cl₂ is formed. The PEt₃ complex undergoes halide exchange with excess of Br^– or l^– to give [PtX(PEt₃)(dppa)]X. The compound [PtCl₂(dppa)] has been prepared from [PtCl₂(cod)](cod = cycloocta-1, 5-diene). The products have been characterised by ³¹P-{¹H}, ¹⁹⁵Pt and ¹H NMR spectroscopy, microanalysis and FAB mass spectrometry. The molecular structures of [PtCl(PMe₂Ph)(dppa)]Cl·1. 5CHCl₃, [PtCl(PBuⁿ₃)(dppa)]Cl and [Pt(dppe)(dppa)]Cl₂·CH₂Cl₂ have been determined by single-crystal X-ray diffraction, and show a square-planar arrangement around the platinum with the dppa acting as a chelate through both phosphorus atoms to give a four-membered PtP₂N ring whose geometry is distinctly different from that of the deprotonated systems. All of the dppa NH groups hydrogen bond to an adjacent Cl^– in the solid state.