Aromatic Metalation Reactions by Palladium(II) and Platinum(II) on Aromatic Aldoximes and Ketoximes

Ortho metalation by palladium(II) was observed in the reaction of lithium tetrachloropalladate(II) with various aromatic aldoximes and ketoximes in methanol in the presence of sodium acetate. The obtained chloro-bridged complexes(7) possessed both ortho-attached palladiumcarbon σ-bonding and palladium-nitrogen coordinate bonding to oximes. Reactions of O-acyl and O-methyl oximes with lithium tetrachloropalladate(II) were also carried out. An ortho metalation was observed in the former case, but dichlorobis(O-methyl oxime)palladium(II) type complexes containing no palladium-carbon σ-bonds were predominantly formed in the latter case. The bridge-splitting reaction of chloro-bridged complexes with triphenylphosphine and the metathetic reaction with sodium bromide in acetone were carried out. In the case of potassium tetrachloroplatinate(II), an ortho metalation reaction was observed giving the complexes(10) but chloro-bridged complexes could not be isolated.