Fluorenides

E. Reduction of Halomethyl Phenyl Sulfones and Chloromethyl Phenyl Sulfoxide by Fluorenide Anions... 

Another example of path a of Scheme 1.15 is the anion-radical derived from fluorene. It undergoes a first-order decay to give the conjugate base (the fluorenide anion) and a hydrogen atom (Casson and Tabner 1969) according to Scheme 1.16. 

A new development in silsesquioxane ehemistry is the eombination of sil-sesquioxanes with cyclopentadienyl-type ligands. Reeently, several synthetie routes leading to silsesquioxane-tethered fluorene ligands have been developed. The scenario is illustrated in Seheme 47. A straightforward aeeess to the new ligand 140 involves the 1 1 reaction of 2 with 9-triethoxysilylmethylfluorene. Alternatively, the chloromethyl-substituted c/oxo-silsesquioxane derivative 141 can be prepared first and treated subsequently with lithium fluorenide to afford 140. Compound 141 has been used as starting material for the preparation of the trimethylsilyl and tri-methylstannyl derivatives 142 and 143, respeetively, as well as the novel zirconoeene complex 144. When activated with MAO (methylalumoxane), 144 yields an active ethylene polymerization system. 

A stable representative 31 of an intermediate 29 was obtained in 40% yield by Komatsu upon reacting Cjq with potassium fluorenide in the presence of neutral fluorene without rigorous exclusion of air (Scheme 10.5) [45]. 

We have mentioned previously as a stable ylide dimethyl sulfonium fluorenide (see Section 2.9). It yielded the first example (1938) of a [2,3] sigmatropic rearrangement of a sulfur ylide [505, 506] (Sommelet-Hauser rearrangement). 

Fluorenide derivatives, alkali compounds, 2, 13 Fluorenyl-amido complexes with Ti(IV), 4, 438, 4, 455 with Zr(IV), 4, 788 Fluorenyl complexes... 

The X-ray and solution structures of lithium fluorenide (68) have been reported earlier125,126. It was found that whereas the X-ray study suggested that the lithium is asymmetrically positioned above the fluorenyl unit, calculations and solution 13C NMR showed a symmetrical structure. Thus, Johnels and Edlund used 13C cross-polarization/magic angle spinning (CP/MAS) NMR in order to get further insight about the structure 68. 

The tetraphenylcyclopentadienide and the fluorenide carbanions were photodimethylated by DMSO in a quite similar way [133]. 

Whereas the spectral behavior of solvent-separated ion pairs and free ions is very similar, the UV/Vis spectra of contact and solvent-separated ion pairs are usually different from each other, as has been shown with sodium fluorenide [141, 164]. Due to the penetration of solvent molecules between the ion-pair couples, the direct influence of the metal cation on the r-electron system of the carbanion is lost. With increasing dissociation, the absorption maximum of sodium fluorenide in tetrahydrofuran solution is shifted bathochromically in the direction of the absorption maximum of the free... 

Basicity is measured in terms of a thermodynamic equilibrium involving coordination with H+. Nucleophilicity is measured in terms of the rates of reaction with the most varied electrophiles. Hence, although a correlation between basicity and nucleophilicity is often found (generally Sn reactions are faster with the stronger bases), it is by no means a priori necessary. An example of a direct simple relationship between nucleophilicity and basicity in Sn2 reactions is the reaction of 9-substituted fluorenide ions with (chloromethyl)benzene in dimethyl sulfoxide solution [595]. 

Just as the one electron reduction of a neutral molecule produces an anion radical, the one electron reduction of an organic anion can yield a dianion radical, assuming that the LUMO of the anion is not too high in energy. Two anions familiar in organic chemistry are the dibenzoylmethide (an enolate of a 6-diketone) [112] and fluorenide anions [113] (Scheme 68). 

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