Subtle ligand/media effects. Modulation of cis/traps isomerism in hydrogen peroxide oxidation of Pt(II) to Pt(IV) complexes

Abstract

The modulation of cis/trans isomerism on the oxidation of Pt-II to Pt-IV via subtle ligand/media effects has been established. The reaction of [Pt-II(O-O)(dpda)] (O-O = 1,1-cyclobutanedicarboxylate (cbdc), dibenzylmalonate (dbm); dpda = 2,2-dimethyl-1,3-propanediamine) with hydrogen peroxide in acetic acid produces cis-[Pt-IV(O2CCH3)(2)(O-O)(dpda)]; while the reaction in acetic anhydride gives trans-[Pt-IV(O2CCH3)(2)(O-O)(dpda)]. The crystal structures of cis[Pt-IV(O2CCH3)(2)(cbdc)(dpda)] (orthorhombic Pbca, a = 11.148(2) Angstrom, b = 14.188(5) Angstrom, c = 23.425(3) Angstrom, V = 3705(2) Angstrom(3), Z = 8, R = 0.0525) and trans- [Pt-IV(O2CCH3)(2)(cbdc)(dpda)].3H(2)O (monoclinic P2(1)/c, a = 11.479(2) Angstrom, b = 13.426(3) Angstrom, c = 14.640(5) Angstrom, beta = 108.73(2)degrees, V = 2136.8(9) Angstrom(3), Z = 4, R = 0.0251) have been solved and refined. The AcO-Pt-AcO angle (87.4(5)degrees) of the cis isomer presents a striking contrast to that (172.5(1)degrees) of the trans isomer. The trans isomer is retained in aqueous solution, but the cis isomer is very slowly converted to the trans isomer in both water and acetic acid.