Hydrogen peroxide oxidation of di(hydroxo)platinum(II) species in carboxylic acids

A facile procedure for synthesizing the mono(hydroxo)tris(carboxylato)platinum(IV) species has been achieved. The reaction of [Pt-II(OH)(2)(dmpda)] (dmpda = 2,2-dimethyl-1,3-propanediamine) with a 30% aqueous solution of H2O2 in the presence of a carboxylic acid produces a stable [Pt-IV(OOCR)(3)(OH)(dmpda)] (R = Me, Et) complex in high yield. The crystal structures of [Pt-IV(OOCMe)(3)(OH)(dmpda)].H2O (triclinic P1 bar, a = 8.761(2) Angstrom, b = 9.245(3) Angstrom, c = 10.659(2) Angstrom, alpha = 106.25(2)degrees, beta = 93.90(2)degrees, gamma = 98.92(2)degrees, V = 813.1(3) Angstrom(3), Z = 2, R = 0.0474) and [Pt-IV(OOCEt)(3)(OH)(dmpda)] (monoclinic P2(1)/c, a = 12.777(4) Angstrom, b = 10.514(2) Angstrom, c = 14.971(3) Angstrom, beta = 107.40(2)degrees, V = 1919.2(8) Angstrom(3), Z = 4, R = 0.0611) show that the hydroxyl group has been selectively positioned at an axial site. The intramolecular hydrogen bond between the OH and C=O moiety exists (O(H)...O= C, 2.83 Angstrom for [Pt-IV(OOCMe)(3)(OH)(dmpda)].H2O; 2.72 Angstrom for [Pt-IV(OOCEt)(3)(OH)(dmpda)]. Formation of the axialmono(hydroxo)tris(carboxylato)platinum( IV) species may be ascribed to a combination of 'reactive-equatorial effects' with 'cis-addition' in the carboxylic acid.