Synthesis and structure of highly substituted pyrazole ligands and their complexes with platinum(II) and palladium(II) metal ions

• Published in: Tetrahedron 2004-02, Vol.60 (8), p.1749-1759
• Main Authors: Budzisz, Elzbieta, Malecka, Magdalena, Nawrot, Barbara
• Format: Article
• Language: English
• Subjects: Palladium(II) complex; Phosphonic chromone; Platinum(II) complex; Pyrazole; X-ray structure
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2003.12.044

Reaction of 3-methoxycarbonyl-2-methyl- or 3-dimethoxyphosphoryl-2-methyl-substituted 4-oxo-4 H-chromones 1 with N-methylhydrazine resulted in the formation of isomeric, highly substituted pyrazoles 4 (major products) and 5 (minor products). Intramolecular transesterification of 4 and 5 under basic conditions led, respectively, to tricyclic derivatives 7 and 8 . The structures of pyrazoles 4a (dimethyl 2-methyl-4-oxo-4 H-chromen-3-yl-phosphonate) and 4b (methyl 4-oxo-2-methyl-4 H-chromene-3-carboxylate) were confirmed by X-ray crystallography. Pyrazoles 4a and 4b were used as ligands (L) in the formation of ML 2Cl 2 complexes with platinum(II) or palladium(II) metal ions (M). Potassium tetrachloroplatinate(II), used as the metal ion reagent, gave both trans-[Pt( 4a ) 2Cl 2] and cis-[Pt( 4a ) 2Cl 2], complexes with ligand 4a , and only cis-[Pt( 4b ) 2Cl 2] isomer with ligand 4b . Palladium complexes were obtained by the reaction of bis(benzonitrile)dichloropalladium(II) with the test ligands. trans-[Pd( 4a ) 2Cl 2] and trans-[Pd( 4b ) 2Cl 2] were the exclusive products of these reactions. The structures of all the complexes were confirmed by IR, 1H NMR and FAB MS spectral analysis, elemental analysis and Kurnakov tests. The 3-phosphonic- and 3-carboxylic-chromones react with N-methylhydrazine to give substituted pyrazoles, new ligands for formation of Pt(II) and Pd(II) complexes.