Stereospecific Polymerization of Isoprene with Nd(BH4)3(THF)3/MgBu2 as Catalyst

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Abstract
Summary: The neodymium trisborohydride Nd(BH4)3(THF)3 (THF = tetrahydrofuran) has been used as a catalyst precursor for isoprene polymerization for the first time. Associated to an excess of Al(Et)3, the resulting catalyst is moderately active, giving a mixture of cis‐ and trans‐ polymer. Addition of a stoichiometric amount of MgBu2 to Nd(BH4)3(THF)3 affords a stereospecific catalyst providing trans‐1,4‐polyisoprene, more than 96% regular. That dual component Nd/Mg system also shows a better efficiency and good control of the molecular weights. A molecular structure is tentatively attributed to a bimetallic active species, based on 1H NMR experiments. Possible Nd/Al and Nd/Mg active initiating species. image Possible Nd/Al and Nd/Mg active initiating species.