Divalent transition metal β-keto-enolate complexes as lewis acids

Graddon, DP

doi:10.1016/s0010-8545(00)80090-9

Cited by 212 publications

(7 citation statements)

References 98 publications

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“…While the m -xylylene bridged system was too small to incorporate a guest molecule within the cavity, the 2,7-naphthylidenediylbis(methylene) bridged complex 1 showed a significantly larger cavity. Addition of Lewis bases resulted in equilibrium constants for binding of pyridine ( K = 0.5 L/mol), pyrazine ( K = 5 L/mol), and quinuclidine ( K = 7 L/mol) to complex 1 comparable to those in the literature for binding to Cu(acac) 2 . While these results did not speak for an internal bridging, the much larger equilibrium constants for diazabicyclo[2,2,2]octane ( K = 220 L/mol) showed selective internal binding.…”

Section: Potential Applications For Metal-based Polygons and Polyhedrasupporting

confidence: 54%

Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

2000

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Section: Potential Applications For Metal-based Polygons and Polyhedrasupporting

confidence: 54%

Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

2000

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“…Nature of the Active Catalyst. In the solid state, the Co(II) and Ni(II) bis(acetylacetonate) are respectively tetrameric and trimeric, while Cu(II) is monomeric . In solution in noncoordinating solvents, the oligomeric structures are in equilibrium with monomeric species.…”

Section: Resultsmentioning

confidence: 99%

Catalysis of the Silica Sol−Gel Process by Divalent Transition Metal Bis(acetylacetonate) Complexes

2000

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Transition metal bis(acetylacetonate) complexes of Co(II), Ni(II), Cu(II), and Zn(II) have been found to be active catalysts for the sol-gel process. The catalytic activity of these complexes decreases in going from Co(II) to Zn(II) and is highest for the acetylacetonate ligand system. 29Si NMR studies show that the complexes act primarily as condensation catalysts and are, in that regard, similar to Brønsted bases such as hydroxide. Mechanistically, however, they appear to differ significantly from hydroxide in how they induce condensation. This is revealed in the catalyst concentration dependence, which is 1/2 order for the metal complexes and 1st order in hydroxide. Differences are also apparent in the thermochemical parameters that indicate that the metal complexes act to increase the entropy of the transition state leading to condensation. The catalytic activity is proportional to the degree of ligand dissociation of the metal complex, and experiments suggest that the active catalytic species is specifically the first dissociation product, MII(acac)+.

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“…In the presence of a Lewis base, the cobalt and nickel acetylacetonates exist as the labile monomers trans-M(acac),L, (M = Co, Ni; L = Lewis base) (12). work an alcohol, the proton resonances of L shift towards the resonance positions of the complex Co(acac),L,.…”

Section: Discussionmentioning

confidence: 99%