Direct synthesis of (imine)platinum(ii) complexes by iminoacylation of ketoximes with activated organonitrile ligands

Abstract

The metal-mediated iminoacylation of ketoximes R₁R₂CNOH (1a R₁ = R₂ = Me; 1b R₁ = Me, R₂ = Et; 1c R₁R₂ = C₄H₈; 1d R₁R₂ = C₅H₁₀) upon treatment with the platinum(II) complex trans-[PtCl₂(NCCH₂CO₂Me)₂] 2a with an organonitrile bearing an acceptor group proceeds under mild conditions in dry CH₂Cl₂ to give the trans-[PtCl₂{NHC(CH₂CO₂Me)ONCR₁R₂}₂] 3a–d isomers in moderate yield. The reaction of those ketoximes with trans-[PtCl₂(NCCH₂Cl)₂] 2b under the same experimental conditions gives a 1 : 1 mixture of the isomers trans/cis-[PtCl₂{NHC(CH₂Cl)ONCR₁R₂}₂] 3e–h and 4e–h in moderate to good yield. These reactions are greatly accelerated by microwave irradiation to give, with higher yields (ca. 75%), the same products which were characterized by IR and ¹H, ¹³C and ¹⁹⁵Pt NMR spectroscopies, FAB-MS, elemental analysis for the stable trans isomers, and X-ray diffraction analysis (3f). The diiminoester ligand in 3a was liberated upon reaction of the complex with a diphosphine.