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Coordination chemistry of cyclopentadienyl titanium carboxylates and related complexes

Dang, Y.

Coordination chemistry reviews, 1994-11, Vol.135, p.93-128 [Periódico revisado por pares]

Elsevier B.V

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  • Título:
    Coordination chemistry of cyclopentadienyl titanium carboxylates and related complexes
  • Autor: Dang, Y.
  • É parte de: Coordination chemistry reviews, 1994-11, Vol.135, p.93-128
  • Descrição: The coordination chemistry of cyclopentadienyltitanium carboxylate and its related complexes has been reviewed, with an emphasis on developments in the last decade. The syntheses of these coordination compounds can be carried out in different media, i.e. organic, aqueous or even two-phase systems. The aqueous-phase synthesis provides a complementary method for some compounds. By using di- and tetracarboxylic acids, the two-phase system has proven to be very effective for the preparation of novel multinuclear cyclic molecules and polymers, depending upon the reaction conditions. Thus, a variety of new complexes have been prepared and charactsrized. The molecular structures of most cyclopentadienyltitanium carboxylates have revealed a tetracoordinate, pseudo-tetrahedral coordination geometry. Pentaand higher coordinate complexes have also been reported recently and their structures determined by X-ray analyses. A commonly used criterion for distinguishing the M-OOCR coordination mode is the frequency difference between the asymmetric and symmetric OCO stretching modes ( i.e. Δv= v(OCO) as- v(OCO) g), which is 200 cm −1 or more for monodentate bonding and up to 100 cm −1 for chelating bonding. The X-ray data are more supportive for determining the Ti-OOCR bonding nature, and these data have confirmed the monodentate nature of the two carboxylate ligands in Cp 2Ti(OOCR) 2 and that of the one carboxylate ligand in Cp 2TiCl(OOCR) complexes. Titanocene carboxylates react with various amines to give amides, this is a new method using organometallics for peptide synthesis under severe conditions. The nuclear magnetic resonance data of meta- and para-substituted benzoate titanocenes of the type Cp 2Ti(OOCC 6H 4X) 2 have been analysed, showing good to excellent correlations between the chemical shifts and substituent parameters. The results also indicate a long-range interaction between the substituent X and the cyclopentadienyl ring carbon atoms. In the search for new antitumor agents, some titanocene carboxylates have been tested and found to be active against Ehrlich ascites tumor. In comparison with titanocene dihalides, for example, the hydrogenmaleinate complex is fairly soluble in water and the toxicity of titanocene trichloroacetate is particularly low.
  • Editor: Elsevier B.V
  • Idioma: Inglês
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