Synthesis, multinuclear magnetic resonance and crystal structures of Pt(II) complexes containing amines and bidentate carboxylate ligands

Abstract

A novel synthetic method for the synthesis of the complexes cis-Pt(amine) 2R(COO) 2 is compared to two other methods involving the use of either barium dicarboxylate or sodium carboxylate. Pt(II) compounds with monodentate and bidentate amines were studied. The reaction involves the use of a silver dicarboxylato complex, which is the intermediate in the new synthetic procedure. The crystal structure of the silver intermediate with the ligand 1,1-cyclobutanedicarboxylate (1,1-CBDCA) was determined by X-ray diffraction. The crystal Ag 2(1,1-CBDCA) has a very interesting 3-D extended structure. The complexes cis-Pt(amine) 2R(COO) 2 were studied in solution by multinuclear ( 1H, 13C and 195Pt) magnetic resonance spectroscopy, but the solubilities are very low. D 2O was found to be the best solvent. In 195Pt NMR, the complexes containing bidentate amines forming five-membered chelates were observed at higher fields than those containing monodentate amines. The resonances of the NH 3 compounds were also found at lower fields than the primary amine complexes. All the dicarboxylato ligands form six-membered chelates except 1,2-CBDCA, whose Pt(II) compounds were observed at lower fields than the others. The crystal structures of Pt(en)(1,1-CBDCA), Pt(Meen)(1,1-CBDCA) and Pt(en)(benzylmalonato) were confirmed by X-ray diffraction methods. Several compounds are disordered. The crystals are stabilized by intermolecular hydrogen bonds between the –NH 2 groups and the carboxylato O atoms.