| Summary: | 3,4-Enhanced polymerization of isoprene catalyzed by late transition metal with high activity remains one of the great challenges in synthetic rubber chemistry. Herein, a library of [N, N, X] tridentate iminopyridine iron chloride pre-catalysts (<b>Fe 1–4</b>) with the side arm were synthesized and confirmed by the element analysis and HRMS. All the iron compounds served as highly efficient pre-catalysts for 3,4-enhanced (up to 62%) isoprene polymerization when 500 equivalent MAOs were utilized as co-catalysts, delivering the corresponding high-performance polyisoprenes. Furthermore, optimization via single factor and response surface method, it was observed that the highest activity was obtained by complex <b>Fe 2</b> with 4.0889 × 10<sup>7</sup> g·mol(Fe)<sup>−1</sup>·h<sup>−1</sup> under the following conditions: Al/Fe = 683; IP/Fe = 7095; t = 0.52 min.
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