Publication | Closed Access
Iron-Mediated Coupling of Carbon Dioxide and Ethylene: Macrocyclic Metallalactones Enable Access to Various Carboxylates
46
Citations
34
References
2018
Year
Treatment of (<sup>iPr</sup>PDI)Fe(N<sub>2</sub>)<sub>2</sub> (<sup>iPr</sup>PDI, 2,6-(2,6-iPr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>N═CMe)<sub>2</sub>C<sub>5</sub>H<sub>3</sub>N) with CO<sub>2</sub> and ethylene resulted in the formation of a homologous series of saturated and unsaturated iron carboxylate products, (<sup>iPr</sup>PDI)Fe(O<sub>2</sub>CR), the distribution of which depends on the ratio of the reagents. The solid-state and electronic structures of a saturated product, (<sup>iPr</sup>PDI)Fe(O<sub>2</sub>CC<sub>2</sub>H<sub>5</sub>), were elucidated. Product distributions, deuterium labeling studies, and stoichiometric experiments support initial formation of a five-membered metallalactone intermediate, which undergoes subsequent ethylene insertions to generate macrocyclic metallalactones. Competitive β-hydride elimination, CO<sub>2</sub> insertion, or reaction with H<sub>2</sub> determines the fate of the metallalactone, the latter accounting for formation of iron complexes with saturated carboxylates. Similar reactivity was observed upon addition of propiolactone and ethylene to (<sup>iPr</sup>PDI)Fe(N<sub>2</sub>)<sub>2</sub>, supporting C-O oxidative addition and C-C bond formation through metallacycle intermediates.
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