A solution and solid state study of niobium complexes University of ...

Chapter 2
metal ions, usually forming a six-membered chelate ring [Fig 2.2]. Acetylacetone is
also capable of keto-enol tautomerism; the tautomers exist in equilibrium with each
other and structurally they occupy a syn conformation and a cis configuration [Fig
2.1]. 55
Figure 2.2: Metal complexation by an acetylacetonate anion.
Although acetylacetonate complexes of many metal ions are well known, relatively
few compounds have been reported for niobium, especially in the plus five oxidation
state. 56
2.6.1 Tetrakis(β-diketonate) niobium(IV) complexes:
2.6.1.1 [Nb(thd)4]
The first niobium(IV) tetrakis β-diketonate complex to be characterized by X-
ray crystallography, was published in 1975 by Pinnavaia et al. 57 The aim of
the study was to fully characterize the coordination geometry of a tetrakis
coordinated tetramethylheptanedionate (thd) complex of niobium. The final
55
D. J. Otway, W. S. Rees Jnr, Coordination Chemistry Reviews, 210, 281, 2000
56
F. H. Allen, Acta Cryst., B58, 380, 2002.
57
T. J. Pinnavaia, B. L. Barnett, G. Podolsky, A. Tulinsky, J. Am. Chem. Soc., 97, 2712, 1975.
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