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

The complexes [PtCl(PR3)(dppa)]Cl (PR3 = PMe3, PMe2Ph, PMePh2, PBu3n, 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 I- 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 P-31-{H-1}, Pt-195 and H-1 NMR spectroscopy, microanalysis and FAB mass spectrometry. The molecular structures of [PtCl(PMe2Ph)(dppa)]Cl.1.5CHCl3, [PtCl(PBu3n)(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.