CLUSTERS 3-diketonates

Controlled methanolysis of FeCh in the presence of /3-diketones and of LiOMe or NaOMe in anhydrous methanol gives cyclic hexanuclear yellowish-red cationic clusters [MFeg(OMe)i2L6] (LH = e.g., PhCFl2COCH2COCH2Ph M = Li, Na), in which the Feg(OMe)i2 unit accommodates the alkali metal cation, both in the solid state and in solution. 

Other donor adducts of monodentate ligands, such as MeOH and H20, are known and have been structurally characterized.172 These are typically lower-nuclearity clusters compared to the parent Ba( /3-diketonate), which probably accounts for many observations associated with the improvement of precursor transport in the presence of these additives. 

Despite the interest in group 2 bis(alkoxides) and bis(/3-diketonates) as precursors to metal oxides via CVD routes, systematic studies that correlate their structure and volatility still are few. The solid-state structures of many bis(alkoxides) used for CVD work are not known, and the identity of the materials may vary greatly depending on then-mode of preparation. As shown above, the widely used bis(/3-diketonate) derivative Ba(tmhd)2 for example, has that formula only if prepared under rigorously anhydrous conditions in the presence of moisture the pentanuclear cluster Ba5(tmhd)9(H20)3(OH) can form. Such uncertainties make the identification of trends in volatilities difficult. 

Oligopyrrolic clusters with thiophene spacers 88 have been synthesized and their ability to bind phosphate in the solution phase evaluated <03TL6695>. Tetrathiafulvalene (TTF) analogs consisting of fused thiophenes 89-91 have been synthesized and the mechanism of formation of TTF derivatives from 1,8-diketones has been analyzed <03T8107>. 

Figure 2.36 Molecular structure of [Gd(L )3(H20)]-4H20 co showing 30% ellipsoids with all H atoms and lattice solvent molecules removed [43]. (Reproduced with permission from RC. Andrews, G.B. Deacon, R. Frank, B.H. Fraser, P.C. Junk, et al., Formation of Ho trinuclear clusters and Gd monodimensional polymers induced by ortho and para regioisomers of pyridyl-functionahsed fi-diketones synthesis, structure, and magnetic properties, European Journal of Inorganic Chemistry, 2009, 6, 744-751. Wiley-VCH Verlag GmbH Co. KGaA.)...

Figure 2.41 (a) Solid state structure of [Y6(L )6(HL )4( X3-OH)2(MeOH)4], hydrogen atoms and solvents of crystallization are omitted for clarity (b) the yttium oxo core of the cluster (HL )4( X3-OH)2(MeOH)4] omitting carbon and hydrogen atoms [75]. (Reprinted from Polyhedron, 28, A.K. Jami, RV.V.N. Kishore and V. Baskar, Functionalised P-diketone assisted self-assemhly of a hexanuclear yttrium oxo-hydroxo cluster, 2284-2286, 2009, with permission from Elsevier.)... 

Figure 2.43 (a) [Lns] clusters, hydrogen atoms have been removed for clarity (b) view of the cluster where ligands have been removed for clarity [77]. (Reproduced from S. Petit, F. Baril-Robert, G. Pilet, C. Reber and D. Luneau, Luminescence spectroscopy of europium(III) and terbium(III) penta-, octa-and nonanuclear clusters with fS-diketonate ligands, Dalton Transactions, 34, 6809-6815, 2009, by permission of the Royal Society of Chemistry.)... 

Andrews, PC., Beck, T., Fraser, B.H., etal. (2009) FunctionaUsed P-diketonate polynuclear lanthanoid hydroxo clusters synthesis, characterisation, and magnetic properties. Polyhedron, 28, 2123-2130. 

Andrews, P.C., Deacon, G.B., Frank, R., et al. (2009) Formation of Ho trinuclear clusters and Gd monodimensional polymers induced by ortho and para regioisomers of pyridyl-functionalised P-diketones synthesis, structure, and magnetic properties. European Journal of Inorganic Chemistry, 744-751. 

Jami, A.K., Kishore, P.V.V.N., and Baskar, V. (2009) Functionalised -diketone assisted self-assembly of a hexanuclear yttrium oxo-hydroxo cluster. Polyhedron, 28, 2284—2286. 

Petit, S., Baril-Robert, F., Pilet, G, etal (2009) Luminescence spectroscopy of europium(lll) and terbium(lll) penta-, octa- and nonanuclear clusters widi -diketonate ligands. Dalton Transactions, 6809—6815. 

A combination of two square-pyramids of [Ln5((jt4-OH)( X3-OH)4] with one hollow octahedron of [Ln6([X3-OH)8] by vertex-sharing leads to the assembly of esthetically pleasing tetradecanuclear complexes with a rod-like cluster core (Figure 6.16). Complexes characterized by such a core have been successfully prepared using aryloxide [34, 35], P-diketonate [87], and amino acid ligands [104],... 

In addition, hybrid materials have been made by doping diketonate cluster complexes of lanthanide hydroxide into organic polymers. The resulting materials exhibit lowered coefficients of thermal expansion, increased moduli, reduced solvent sensitivity while preserving acceptable thermal and mechanical properties [110]. 

Eu(dpm)3 is a metal chelate (chele, Greek, claw). The /3-diketone dipivaloylmethane (2,2,6,6-tetramethylheptane-3,5-dione) is a ligand—in this case a bidentate ligand—attached to the europium at two places. Since Eu is hexacoordinate, three dipivaloylmethane molecules cluster about this metal atom. However, when a molecule with a basic group like an amine or an alcohol is in solution with Eu(dpm)j the europium will expand its coordination sphere to complex with this additional molecule. Such a complex is weak and so its nmr spectrum is an average of the complexed and uncomplexed molecule. 

In the field of nanoscale materials, /3-diketonate ligands play an important role as assembly agents in the preparation of high-spin molecules. For example, Fe3+ and Mn3+ clusters containing /3-diketonate donors have shown interesting magnetic anisotropic behavior, also being able to entrap alkaline ions.37,38... 

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