Lithium isodicyclopentadienide

Paquette, Schleyer and coworkers reported that lithium isodicyclopentadienide adopted structures similar to 59 and 6046. An equilibrium was proposed between externally solvated triple ion containing dimer, (A- Li+ A-) Li+ (THF) , and a monomeric contact ion-paired species (A- Li+) (THF) . Lithium-7 NMR obtained as a function of temperature revealed the operation of two exchange processes 1) exchange of Li+ between its sandwiched and contact sites with AH = 8.6 0.5 kcalmoU1 and AS = 3.2 2.7 eu... 

VI. OTHER SUPRAMOLECULAR DIMERS WITH LITHIUM A. Dimers of Lithium Isodicyclopentadienide and Cyclopentadienide... 

The stereoselective reaction of lithium isodicyclopentadienide (50) with methyl iodide and trimethylchlorosilane shows an amazing dependency on temperature. Electrophilic attack at the endo face occurs at —78 °C in THF, whereas 50 is attacked from the exo face at room temperature (Figure 15)84. 

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