Synthesis and multinuclear magnetic resonance spectroscopy of the novel ionic Pt(II) mixed-ligands complexes cis- and trans-[Pt(amine)2(pyrimidine)2](NO3)2

Abstract

Abstract Novel ionic mixed-ligands complexes of the types cis- and trans-[Pt(amine)2(pm)2](NO3)2 (where pm = pyrimidine) were synthesized and studied in the solid state by IR spectroscopy and in aqueous solution by multinuclear (195Pt, 1H and 13C) magnetic resonance spectroscopy. The results of the solution NMR characterization have shown that the isolated compounds are pure. In 195Pt NMR, the cis RNH2 complexes were observed at slightly lower fields (ave. −2441 ppm) than the equivalent trans analogues (ave. −2448 ppm). For Me2NH, the difference between the two isomers is larger (29 ppm). The complexes are observed at lower fields (difference of 100 ppm) than the corresponding [Pt(amine)4]2+ complexes, which might indicate the presence of π-backdonation in the Pt–pm bond. In 1H NMR, the coupling constants 3J(195Pt–1Hamine) are larger in the cis compounds (38–48 Hz) than in the trans analogues (30–36 Hz). The 3J(195Pt–1Hpm) values are also larger for the cis isomers. In 13C NMR spectroscopy, the coupling constants 3J(195Pt–13Camine) are 36 Hz (ave.) for the cis complexes and 26 Hz (ave.) for the trans isomers, while the 2J(195Pt–13Camine) are 18 Hz (cis) and 14 Hz (trans), respectively. The 3J(195Pt–13C5(pm)) values are 36 Hz (cis) and 28 Hz (trans). A few 2J(195Pt–13Cpm) couplings were observed (7–10 Hz).