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, ButNC, or py yields the complexes [Pt(η3-C3H5)(PPh3) L][BF4](L = CO, CNBut, or py) possibly via the intermediacy of [Pt(η3-C3H5)(PPh3)][BF4]. Excess of But 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.