Difunctional silane, structure

It should also be noted that the viscometric technique can detect the presence of star-shaped aggregates, having the ionic active centers. The addition of ethylene oxide to hydrocarbon solutions of poly(isoprenyl)lithium leads to a nearly two-fold increase in viscosity144). Conversely, this results in an approximately twenty-fold decrease in solution viscosity, after termination by the addition of trimethylchloro-silane. This change in solution viscosity is reflected in the gelation which occurs when difunctional chains are converted to the ionic alkoxy active centers 140,145,146). Branched structures have also been detected 147> by viscometry for the thiolate-lithium active center of polypropylene sulfide) in tetrahydrofuran. 

Summary Disilacyclopentanes containing a heteroelement have been prepared by specific routes starting from bis(lithiomethyl)silanes or bis(lithiomethyI)disilanes. The key reaction in the sequence of synthesis is the reductive cleavage of C-S bonds of bis(phenylthiomethyl)silanes and -disilanes to obtain the corresponding difunctional lithioalkyl compounds. The crystal structures of two novel l,2-disila-4-element-cyclo-pentanes and a spirocyclic disilane were obtained and show strained ring systems. Three reaction sites of l,l,2,2-tetramethyl-4,4-diphenyl-l,2,4-trisilacyclopentane could be activated selectively. 

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