CYCLOPLATINATION OF ARYL AND FERROCENYL OXIMES BY CIS-[PTCL2(OSME2)(2)] AFFORDING EXPECTED PLATINUM(II) AND UNEXPECTED PLATINUM(IV) PRODUCTS

Acetophenone, benzamide, ferrocenyl methyl ketone and ferrocenecarboxa mide oximes reacted with cis-[PtCl2-(dmso)(2)] (dmso = dimethyl sulfox ide) in refluxing methanol to afford the expected platina(II)cycles N, S-trans-[Pt(C-N)CI(dmso)], where C-N stands for the corresponding cycl oplatinated organic ligand. The highest yield : of 51% was observed in the case of the acetophenone oxime complex. The structures of the com plexes were established on the basis of analytical and H-1 NMR data, a nd confirmed by an X-ray diffraction analysis of the platinated ferroc enyl methyl ketone oxime. A cyclic voltammetry study of the latter ind icated that cyclometallation decreases the redox potential of the ferr ocene unit by ca. 200 mV. The reaction of a bulkier analog of acetophe none oxime, viz. 2-methyl-1-phenylbutan-1-one oxime, resulted in the f ormation of the unexpected platinum(rv) complex fac-[Pt(C-N)Cl-3(SMe2) ] revealing a unique combination of oxidative cycloplatination and dms o-deoxygenation processes which occur under rather mild conditions The composition of the platinum(Iv) : compound was established by X-ray c rystallography. The Pt-CI bond distance trans to the phenyl carbon [2. 464(4) Angstrom] is rather large. As a result, the trans chloro ligand undergoes rapid solvolysis in aqueous solution, causing a pH drop. Th e deoxygenation of dimethyl sulfoxide that occurs within the metal co- ordination sphere can be viewed as a model of the action of the metal- dependent redox enzyme dimethyl sulfoxide reductase.