Pyrazole and Pyrazolyl Complexes of cis ‐Bis(2,2′‐bipyridine)chlororuthenium(II): Synthesis, Structural and Electronic Characterization, and Acid‐Base Chemistry

Autor: Weizhong Chen, Brian L. Scott, Hershel Jude, Francisca N. Rein, Reginaldo C. Rocha, Dana M. Dattelbaum
Rok vydání: 2009
Předmět:
Zdroj: European Journal of Inorganic Chemistry. 2009:683-690
ISSN: 1099-0682
1434-1948
DOI: 10.1002/ejic.200801086
Popis: Complexes of the type cis-[Ru(bpy)2(Cl)(L)]+ [bpy = 2,2′-bipyridine; with L = pyrazole (1H), 4-methylpyrazole (2H), and 3,5-dimethylpyrazole (3H)] were synthesized and isolated as hexafluorophosphate salts. The molecular structures of these new complexes were fully characterized by 1H NMR spectroscopy and ESI mass spectrometry, and the crystal structure of 3H·PF6 was determined by X-ray crystallography. Compound 3H·PF6 (C25H24ClF6N6PRu) crystallizes in the monoclinic space group P21/n with a = 12.102(2) A, b = 16.826(3) A, c = 13.016(2) A, β = 92.606(2)°, V = 2647.6(8) A3, and Z = 4. The crystal structure of 3H reveals the formation of an intramolecular hydrogen bond (2.562 A) between the pyrazole N(2)–H site and the chloride ligand. The redox and electronic absorption properties of 1H, 2H, and 3H, as well as their deprotonated counterparts [L = pyrazolate (1), 4-methylpyrazolate (2), and 3,5-dimethylpyrazolate (3)], were investigated by cyclic voltammetry and UV/Vis spectroscopy. For detailed analysis of the electronic nature of this series of pyrazolyl ligands, the results are discussed along with other relevant cis-[Ru(bpy)2(X)(Y)]n+ complexes. From spectrophotometric pH titrations, the basicity associated with the coordinated pyrazole/pyrazolate couple in water was found in all three cases to be unusually high, partly owing to the N–H···Cl hydrogen bond that stabilizes the protonated, azole state. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Databáze: OpenAIRE
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