Synthesis, IR and multinuclear NMR spectroscopies and crystallographic studies of complexes of the type cis- and trans-Pt(pyridine)2(NO3)2

Compounds of the type cis- and trans-Pt(Ypy)2(NO3)2 (Ypy=pyridine or its methyl derivatives) have been synthesized and characterized by IR and multinuclear (195Pt, 13C and 1H) NMR spectroscopies. The 195Pt NMR resonances of the trans complexes were observed at lower fields (ave. −1450 ppm) than the cis analogs (ave. −1509 ppm). The complexes containing a methyl substituent in ortho position on the pyridine ligand were observed at lower fields than the others. The coupling constants 3J(195Pt–1H) and 3J(195Pt–13C) are larger in the cis configuration (ave. 44 and 46 Hz, respectively) than in the trans analogs (ave. 33 and 35 Hz, respectively). The covalent character of the PtO bond seems greater in the trans complexes than in the cis compounds. The crystal structures of cis-Pt(3,5-lut)2(NO3)2, cis-Pt(2-pic)2(NO3)2, cis-Pt(py)2(NO3)2·1/2CH2Cl2, trans-Pt(3,5-lut)2(NO3)2 and trans-Pt(py)2(NO3)2 were determined. Except for the cis pyridine complex, which contains some molecules of solvent, the two nitrato groups are on opposite sides of the coordination plane. The trans influence of the different ligands is compared.