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 (Pt-195, C-13 and H-1) NMR spectroscopies. The Pt-195 NMR reso nances of the trans complexes were observed at lower fields (ave. - 1450 pp m.) than the cis analogs (ave. - 1509 ppm). The complexes containing a meth yl substituent in ortho position on the pyridine ligand were observed at lo wer fields than the others. The coupling constants (3)J(Pt-195-H-1) and (3) J(Pt-195-C-13) are larger in the cis configuration (ave. 44 and 46 Hz, resp ectively) 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 th an 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).1/2CH(2)Cl(2), 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 tr ans influence of the different ligands is compared. (C) 2001 Elsevier Scien ce B.V. All rights reserved.