Stereospecific Polymerization of Isoprene with Nd(BH<sub>4</sub>)<sub>3</sub>(THF)<sub>3</sub>/MgBu<sub>2</sub> as Catalyst

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<jats:title>Abstract</jats:title><jats:p><jats:bold>Summary:</jats:bold> The neodymium trisborohydride Nd(BH<jats:sub>4</jats:sub>)<jats:sub>3</jats:sub>(THF)<jats:sub>3</jats:sub> (THF = tetrahydrofuran) has been used as a catalyst precursor for isoprene polymerization for the first time. Associated to an excess of Al(Et)<jats:sub>3</jats:sub>, the resulting catalyst is moderately active, giving a mixture of <jats:italic>cis</jats:italic>‐ and <jats:italic>trans</jats:italic>‐ polymer. Addition of a stoichiometric amount of MgBu<jats:sub>2</jats:sub> to Nd(BH<jats:sub>4</jats:sub>)<jats:sub>3</jats:sub>(THF)<jats:sub>3</jats:sub> affords a stereospecific catalyst providing <jats:italic>trans</jats:italic>‐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 <jats:sup>1</jats:sup>H NMR experiments.</jats:p><jats:p><jats:boxed-text content-type="graphic" position="anchor"><jats:caption><jats:p>Possible Nd/Al and Nd/Mg active initiating species.</jats:p></jats:caption><jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" position="anchor" xlink:href="urn:x-wiley:10221336:media:MARC200300289:gra001"><jats:alt-text>image</jats:alt-text><jats:caption><jats:p>Possible Nd/Al and Nd/Mg active initiating species.</jats:p></jats:caption></jats:graphic></jats:boxed-text> </jats:p>

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