Palladium(II) and platinum(II) derivatives with N,O ligands

Abstract

The preparation of a series of Pd(II) and Pt(II) derivatives with three N,O hybrid ligands 1-(2-pyridyl)ethyldiphenylphosphine oxide, L¹; (2-pyridyl)methyldiphenylphosphine oxide, L² and 2-pyridyldiphenylphosphine oxide, L³ is described. Depending on the ligand to metal molar ratio, either 1∶1 [LMCl₂] {[L¹PdCl₂] 1, [L²PdCl₂] 2, [L³PdCl₂] 3, [L¹PtCl₂] 4} or 2∶1 [L₂MCl₂] {[L¹₂PdCl₂] 5, [L²₂PdCl₂] 6, [L¹₂PtCl₂] 7} adducts are obtained. In addition, an ionic species [L¹₂Pd][PF₆]₂ 8, has been isolated by treatment of complex 5 with AgPF₆. The structures in the solid state of compounds 5b·MeOH·H₂O, 6·MeOH and 4·CH₂Cl₂ have been solved by X-ray diffraction. The structures of trans-[L¹₂PdCl₂] 5b (one of the diastereomers of 5) and trans-[L²₂PdCl₂] 6 are rather different, the former being a chiral molecule (R,R enantiomer) with a C₂ axis perpendicular to the plane of the metal, the latter, 6, being a centrosymmetric molecule. In both the species the ligand is bonded through the nitrogen atom. In complex [L¹PtCl₂] 4, the ligand is coordinated through the N and O atoms to form a six-membered ring which adopts a boat-like conformation. The structure reveals a fairly short interaction between one hydrogen atom of the Me group in an axial position and the platinum atom, Pt· · ·H 2.69 Å. Short contacts Pd· · ·H are also observed in the structures of compounds 5b and 6. Some aspects of the reactivity of the new species are discussed.