N₂ Dissociation vs Reversible 1,2-Methyl Migration in PC_NHCP Cobalt(I) Complexes in the Stereoselective Isomerization (<i>E/Z</i>) of Allyl Ethers

With growing efforts pushing toward sustainable catalysis, using earth-abundant metals has become increasingly important. Here, we present the first examples of cobalt PCNHCP pincer complexes that demonstrate dual stereoselectivity for allyl ether isomerization. While the cationic cobalt complex [((PCNHCP)Co)2-μ-N2][BAr4F]2 (3) mainly favors the Z-isomer of the enol ether, the corresponding methyl complex [(PCNHCP)CoMe] (4) mostly gives the E-isomer. The dichotomy in selectivity was investigated computationally, revealing important contributions from the substituents on the metal (N2 vs Me), including a 1,2-alkyl migration from cobalt to the N-heterocyclic carbene (NHC) of the methyl substituent, which is further explored in this report.