Direct ortho-palladation of 2-phenyl-2-oxazoline: Crystal structure of Cl2Pd(OCH2CH2NCPh)2 and Cl(PPh3)Pd(OCH2CH2NCC6H4)

Direct ortho-palladation of sterically non-hindered 2-phenyl-2-oxazoline (1) using Pd(OAc)2 and AcONa in AcOH provided di-μ-acetatobis-[2-(2-oxazolinyl)phenyl,1-C,3-N]dipalladium(II) (3a) in a yield of 63%. Dimeric complex 3a was converted into the corresponding μ-chloro analog (3b) by the reaction with LiCl in acetone in quantitative yield. Compound 3b was also obtained in 90% yield by the ligand exchange reaction of oxazoline (1) with dimeric ortho-palladated complex of N,N-dimethylbenzylamine in a AcOH–CHCl3 mixture at 50°C. The same reaction at room temperature provided the coordination complex dichlorobis-(2-phenyl-2-oxazoline)palladium(II) (2); the use of toluene in this reaction (50°C) led to the formation of chloro[N,N-dimethylbenzylamino]-(2-phenyl-2-oxazoline)palladium(II) (5). Dimer 3b reacted with 2,4-pentadionate and PPh3 to yield the corresponding mononuclear derivatives 6 and 7, respectively. The structures of coordination complex 2 and phosphane adduct 7 were confirmed by X-ray diffraction analysis. Compound 2 has a centrosymmetric structure with strictly planar coordination environment of the palladium center and a close above-plane approach of the ortho-CH bond to the metal center. In adduct 7, both the palladium coordination sphere and palladacycle are nearly planar.