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

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] {[L1
2PdCl2] 5, [L2
2PdCl2] 6, [L1
2PtCl2] 7} adducts are obtained. In addition, an ionic
species [L1
2Pd][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-[L1
2PdCl2] 5b (one of the diastereomers of 5) and trans-[L2
2PdCl2] 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.