N<sub>2</sub> Dissociation\nvs Reversible 1,2-Methyl\nMigration in PC<sub>NHC</sub>P Cobalt(I) Complexes in the Stereoselective\nIsomerization (<i>E/Z</i>) of Allyl Ethers

With growing efforts pushing toward sustainable catalysis,\nusing\nearth-abundant metals has become increasingly important. Here, we\npresent the first examples of cobalt PC<sub>NHC</sub>P pincer complexes\nthat demonstrate dual stereoselectivity for allyl ether isomerization.\nWhile the cationic cobalt complex [((PC<sub>NHC</sub>P)Co)<sub>2</sub>-μ-N<sub>2</sub>][BAr<sub>4</sub><sup>F</sup>]<sub>2</sub> (<b>3</b>) mainly favors the <i>Z</i>-isomer of the enol\nether, the corresponding methyl complex [(PC<sub>NHC</sub>P)CoMe]\n(<b>4</b>) mostly gives the <i>E</i>-isomer. The dichotomy\nin selectivity was investigated computationally, revealing important\ncontributions from the substituents on the metal (N<sub>2</sub> vs\nMe), including a 1,2-alkyl migration from cobalt to the N-heterocyclic\ncarbene (NHC) of the methyl substituent, which is further explored\nin this report.