engleski

NMR spectroscopic study of monoalkyl /alpha-(4-benzeneazoanilino)-N-benzyl/phosphonates and their palladium(II)complexes

The multinuclear NMR study (1H, 13C and 31P) of monoalkyl esters of /a-(4-benzeneazoanilino)-N-benzyl/phosphonic acid, their sodium salts and two types of metallocyclic complexes of palladium(II), those with C, N and N, O five-membered chelate rings, has been reported. The NMR analysis was accomplished by one- and two-dimensional homo- and heteronuclear in CDCl3 and DMSO-d6 solutions. It was found that free monoalkyl phosphonates are dimers in chloroform solution due to the strong intermolecular hydrogen bonding between the phosphonic acid groups, while in DMSO there is no ligand association. The spectra of both types of complexes are rather complex, caused either by the removal of degeneracy (binuclear C, N cyclopalladated complexes) or by the presence of more isomeric forms (mononuclear N, O chelate complexes). Complexes retain their integrity in chloroform solution, but decompose in DMSO. This solvent with strong complexing ability initiates dissociation of the complex moiety by displacing the organophosphorus ligand. The results obtained by NMR studies are in agreement with those of the mass spectrometry, indicating that the five-membered C, N chelate ring in the binuclear chloro bridged complexes is much more stable than the five-membered N, O ring in the mononuclear chelate complexes.

palladium(II) complex; phosphonate; NMR study

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