Diphenylhexyl lithium

The reaction of n-butyl-lithium with methacrylonitrile in toluene at —75 °C was found to be relatively slow, and as much as 50% of it remained unreacted when the monomer was completely polymerized. In marked contrast, s-butyl-lithium and 1,1-diphenylhexyl-lithium reacted rapidly and completely under the same conditions. It was suggested that the incomplete consumption of n-butyl-lithium was attributable to the formation of stable, mixed aggregates with the propagating centres. 

Recently, polydentate dilithium alkoxides (dilithium triethylene glycoxides) (Scheme 12) have been shown to be suitable additives for the polymerization of methyl methacrylates, as they provide high initiator efficiencies and narrow molecular weight distributions (1.1-1.3). The addition of dilithium triethylene glycoxide to the anionic polymerization of MMA (THF, (l,l-diphenylhexyl)lithium as initiator) resulted in the synthesis of well controlled polymers even at relatively high temperatures. This beneficial effect could be assigned to a better coordination with the enolate ion pairs, thus slowing down the polymerization rates (Table 5) [197]. 

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