A facile procedure for synthesizing the mono(hydroxo)tris(carboxylato)platinum(IV) species has been achieved. The reaction of [Pt II (OH) aqueous solution of H 2 O 2 in the presence of a carboxylic acid produces a stable [Pt IV (OOCR) 3 (OH)(dmpda)] (R ¼ Me, Et) complex in high yield. The crystal structures of [Pt IV (OOCMe) 3 (OH)(dmpda)] AE H 2 O (triclinic P1 bar, a ¼ 8.761(2) Å , b ¼ 9.245(3) Å , c ¼ 10.659(2) Å , a ¼ 106.25(2)°, b ¼ 93.90(2)°, c ¼ 98.92(2)°, V ¼ 813.