Unprecedented single-pot synthesis of nitrile-derived ketoimino platinum(ii) complexes by ring opening of Δ4-1,2,4-oxadiazolines

Abstract

[PtCl₂(RCN)₂] (1a R = CH₂CO₂Me, 1b R = CH₂Cl) prepared upon EtCN replacement at [PtCl₂(EtCN)₂] by the appropriate organonitrile, react with a cyclic nitrone ⁻O–⁺NCHCH₂CH₂C(Me)₂, under mild conditions, to give, in an unprecedented single-pot synthesis involving spontaneous N–O bond cleavage, the ketoimino complexes trans-[PtCl₂{RC(O)NCN(H)C(Me)₂–CH₂CH₂}₂] (2a, 2b) with two (pyrrolidin-2-ylidene)amino ligands. The analogous 2c (R = Et) and 2d (R = Ph) are formed by treatment with H₂, in the absence of any added catalyst, of the Δ⁴-1,2,4-oxadiazoline complexes trans-[PtCl₂{NC(R)ONC(Me)₂CH₂CH₂CH}₂] (3a R = Et, 3b R = Ph) derived from the [2 + 3]-cycloaddition of the cyclic nitrone with the appropriate organonitrile complex of type 1. The compounds were characterized by elemental analyses, IR, ¹H, ¹³C and ¹⁹⁵Pt NMR spectroscopies, FAB mass spectrometry and X-ray structure analyses for 2a and 2d.