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

摘要

Reaction of K[PtCl_3(Me_2SO)] and salicylaldoxime gives trans-(S,N)-[PtCl_2-(o-HOC_6H_4CH=NOH)(Me_2SO)] centre dot H_2O, which contains the oxime coordinated in the unusual ligand monodentate fashion. In the presence of one equivalent KOH the reaction leads to a mixture of cis-(S,N)- and trans-(S,N)-[PtCl(o-OC_6H_4CH=NOH)(Me_2SO)]; 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 deg C for 8 weeks, the geometric cis -> trans isomerization takes place, giving exclusively trans-(S,N)-isomer. Chlorination of both trans-(S,N)-[PtCl_2(o-HOC_6H_4CH=NOH)(Me_2SO)] centre dot H_2O and trans-(S,N)-[PtCl(o-OC_6H_4CH=NOH)(Me_2SO)] with excess Cl_2 results in oxidation 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)-[PtCl_3{Cl_2(O)C_6H_2CH=NOH}(Me_2SO)] which was characterized by X-ray crystallography.