Arylation of styrene derivatives using aryliron complexes [CpFe(CO)2Ar] revealed by density functional theory calculations: Fe(II)-assisted group exchange through Fe–C bond cleavage and Fe–X bond formation

The detailed mechanism for arylation of styrene or its α-CF3 substituted analog using aryliron complex [CpFe(CO)2Ar] was studied using density functional theory calculations. Results of calculations show that the arylation mechanism mainly involves three steps: (1) a ligand exchange process between a CO and styrene or its derivative; (2) migration of Ar group from Fe to β-C of styrene; (3) β-H (or β-F) elimination and dissociation of the stilbene derivative from the CpFeHCO (or CpFeFCO) moiety. Both of Steps (2) and (3) experience a similar four-memberred cyclic transition state. The dπ–pπ interaction stabilizes the CC π coordinated complexes and the agostic interaction plays an important role in stabilizing intermediates and promoting elimination of the β-H (or β-F if available). For arylation of the α-CF3 substituted styrene, our calculations clarified that the dissociation of ethylene derivatives to give PF (product for β-F elimination) is kinetically and thermodynamically more favorable than to give PH (product for β-H elimination), which is the determined step for the selectivity of the final products.

Arylation of Styrene Derivatives Can Be Realized Using Aryliron Complexes [CpFe(CO)2Ar] by Fe(II)-Assisted Group Exchange with Fe-C Bond Cleavage and Fe-X Bond Formation.Figure optionsDownload as PowerPoint slideHighlights
► Arylation mainly involves ligand exchange, Ar migration, and β-H/F elimination.
► Both migration and elimination experience four-memberred cyclic transition state.
► Path1a was determined to be a favorable pathway with dominant trans isomer product.
► dπ–pπ and agostic interactions stabilize intermediates and promote β-H/F elimination.
► β-F elimination is more favorable than β-H elimination in arylation of α-CF3 styrene.