Different chlorination modes of oximes: chlorination of salicylaldoxime coordinated to platinum

Reaction of K [PtCl3(Me2SO)] and salicylaldoxime gives trans-(S,N)- [PtCl2( o-HOC6H4CH=NOH)(Me2SO)]. H2O, which contains the oxime coordinated in the u nusual ligand monodentate fashion. In the presence of one equivalent KOH th e reaction leads to a mixture of cis(S,N)- and trans-(S,N)-[PtCl(o-OC6H4CH= NOH)(Me2SO)] the structure of the cis-(S,N) isomer was determined by X-ray crystallography. On incubation the mixture of the isomers in chloroform or dichloromethane solutions at 20-25 degrees C for 8 weeks, the geometrical c is --> trans isomerization takes place, giving exclusively trans-(S,N)-isom er Chlorination of both trans-(S,N)-[PtCl2(o-HOC6H4CH=NOH)(Me2SO)]. H2O and trans-(S,N)-[PtCl(o-OC6HSCH=NOH)(Me2SO)] with excess Cl-2 results in oxida tion of Pt(II) and instead of the Piloty reaction or oxidative deoximation, chlorination in para and ortho positions of the benzene ring giving, as a result of the overall process, the platinum(IV) complex trans-(S,N)-[PtCl3{ Cl-2(O)C6H2CH=NOH} (Me2SO)] which was characterized by X-ray crystallograph y. (C) 1999 Elsevier Science S.A. All rights reserved.