Ligand-substitution reactions of neutral and cationic allyl(cyclo-octa-1,5-diene)platinum complexes

Abstract

Treatment of the compound [PtX(σ-C₃H₅)(cod)](X = Cl or Br; cod = cyclo-octa-1,5-diene) with pyridine (py) affords [PtX(η³-C₃H₅)(py)]. In solution these complexes dimerise to form allyl-bridged binuclear species. Reaction of the complex [Pt(C₂H₄)₂{P(C₆H₁₁)₃}] with allyl halides, or reaction of [PtX(σ-allyl)(cod)](X = Cl, allyl = C₃H₅ or C₃H₄Ph-3; X = Br, allyl = C₃H₅ or C₃H₄Me-3) with 1 mol of P(C₆H₁₁)₃ affords the compounds [PtX(η³-allyl){P(C₆H₁₁)₃}]. Addition of 2 mol of PPh₃ or P(C₆H₁₁)₃, or 1 equivalent of Ph₂PCH₂CH₂PPh₂(dppe), affords complexes of the type [PtX(allyl)L₂]. Treatment of the salts [Pt(η³-allyl)(cod)][BF₄](allyl = C₃H₅ or C₃H₄Me-3) with py, PPh₃, or dppe gives [Pt(η³-allyl)(L₂)][BF₄](L₂= 2py, 2PPh₃, or dppe). In contrast, 1 mol of PPh₃ followed by 1 equivalent of CO, Bu^tNC, or py yields the complexes [Pt(η³-C₃H₅)(PPh₃) L][BF₄](L = CO, CNBu^t, or py) possibly via the intermediacy of [Pt(η³-C₃H₅)(PPh₃)][BF₄]. Excess of Bu^t NC or py affords the σ-allylic species [Pt(σ-C₃H₅)(PPh₃)L₂][BF₄]. In a similar manner, the tris (trimethyl phosphite) complexes [Pt(σ-allyl){P(OMe)₃}₃][BF₄](allyl = C₃H₅, C₃H₄Me-3, or C₃H₄Ph-3) have been synthesised. Detailed n.m.r. studies (¹H, ¹³C, ³¹P, variable-temperature) of these complexes has led to an understanding of their behaviour in solution.