PtII versus PdII-assisted [2+3] cycloadditions of nitriles and nitrone. Synthesis of nitrile-derived arylamido platinum(II) and Δ4-1,2,4-oxadiazoline palladium(II) complexes

The reactions of bis(organonitrile) platinum(II) complexes trans-[<bold>Pt</bold>Cl-2(N equivalent to CR)(2)] (R = C6H4(p-HC=O), CH2C6H4(p-CH3)) with pyrroline N-oxide-O+N=CHCH2CH2CMe2 afford arylamido platinum(II) complexes trans-[<bold>Pt</bold>Cl-2{(O=CR)N=CCH2CH2CMe2NH}(2)] (R = C6H4(p-HC=O) (<bold>1</bold>), CH2C6H4(p-CH3) (<bold>2</bold>)). The spectral data of <bold>1</bold> and <bold>2</bold> show that the oxadiazoline rings in both cases have opened by a spontaneous N-O bond cleavage to form (Z)-p-formyl-N-(5,5-dimethylpyrrolidin-2-ylidene)benzamide or (Z)-N-(5,5-dimethylpyrrolidin-2-ylidene)-2-p-tolylacetamide ligands, respectively, where the N-atoms of the benzamide or acetamide moieties coordinate to platinum(II) metal centre in trans positions. However, the reactions of bis(organonitrile) palladium(II) complexes trans-[<bold>Pd</bold>Cl-2(N equivalent to CR)(2)] with pyrroline N-oxide furnish Delta(4)-1,2,4-oxadiazoline palladium(II) complexes trans-[<bold>Pd</bold>Cl-2{N equivalent to C(R)ONC(H)CH2CH2CMe2}(2)] (R = C6H4(p-HCO) (<bold>3</bold>), CH2C6H4(p-CH3) (<bold>4</bold>)) as the exclusive detected products. Compounds <bold>1-4</bold> have been characterized by IR, H-1, C-13 NMR spectroscopy, elemental analyses, ESI+-MS and also, in the case of <bold>1</bold>, by single crystal X-ray diffraction analysis. (C) 2018 Elsevier Ltd. All rights reserved.