Reactions of nitrones with transition metal nitrile complexes: cycloaddition, ligand substitution, or hydrolysis

The reaction of nitrones with transition metal nitrile complexes of the type [MCl2(PhCN)2] and [MCl4(MeCN)2] leads to different products, depending on the metal. Reaction of [PdCl2(PhCN)2] with RCHN(Me)O (R=Ph, p-C6H4Me) afford Δ4-1,2,4-oxadiazoline complexes as products of [2 + 3] cycloaddition of the nitrone across the C≡N bond of the nitrile. The oxophilic transition metal compounds [TiCl4(MeCN)2] and [ZrCl4(MeCN)2] undergo rapid ligand exchange to form nitrone complexes from which the nitrone can be released without decomposition. The closely related compounds [MoCl4(MeCN)2] and [WCl4(MeCN)2] mediate the hydrolysis of nitrones to the corresponding aldehydes.