Platinum complexes of (R)-N,N-bis(2-(diphenylphosphino)ethyl)-1-phenyl-ethylamine: their synthesis and characterisation

Both neutral and ionic platinum complexes of (R)-N,N-bis(2-diphenylphosphinoethyl)-1-phenyl-ethylamine (PNP) were synthesised. In the reaction of PtCl2(PhCN)2 and PNP cis-PtCl2(η2-P,P-PNP) (1) was formed coordinating PNP as a P,P-bidentate ligand. Diastereotopic phosphorus atoms were observed in 31P NMR upon addition of SnCl2 to the parent complex (1) due to the formation of [PtCl(PNP)][SnCl3] (2a). The formation of similar complex cations, [PtX(PNP)]+ (where X=I (4), CN (5)) containing PNP as a terdentate ligand was also observed when KI and KCN was added in the presence of SnCl2, which formed trichlorostannate counterion. The addition of PPh3 to 1 resulted in the partial formation of [Pt(PPh3)(PNP)]2+ (3), which could be accomplished upon addition of SnCl2. The catalytic activity of the platinum–PNP system in the hydroformylation of styrene is low.