Applying Na/Co(ii) bimetallic partnerships to promote multiple Co–H exchanges in polyfluoroarenes

Abstract

Heterobimetallic base NaCo(HMDS)3 [HMDS = N(SiMe3)2] enables regioselective di-cobaltation of activated polyfluoroarenes under mild reaction conditions. For 1,3,5-C6H2X3 (X= Cl, F), NaCo(HMDS)3 in excess at 80oC impressively induces the collective...

Cooperative activation of carbon–hydrogen bonds by heterobimetallic systems

“…37). 134,135 Regioselective functionalization of fluoroarenes can be challenging due to uncontrolled reactivity and unwanted side reactions such as benzyne formation or cascade processes (auto-metalation, multi-metalation). 138 Heterobimetallic amide bases combining an alkali metal with a divalent transition-metal center not only prevent these side reactions but also allow new reaction pathways towards thermally stable metalates under mild conditions.…”

“…In contrast to Mulvey's AMMMs, the alkali–metal ions partake in the C–H activation and direct the metalation through intramolecular coordination to the fluorine atoms. The importance of these interactions is further underlined by the fact that the choice of the alkali metal matters, as showcased by considerable differences in reactivity when descending from Li through Na to K. 135 While the reaction of 1,3,5-trifluorobenzene with three equivalents of [NaCo(hmds) 3 ] ( Fig. 37 , bottom) promotes 1,3-dicobaltation, reactions with the same amounts of [LiCo(hmds) 3 ] and [KCo(hmds) 3 ] only lead to monocobaltation or no reaction at all, respectively, even under forcing reaction conditions (16 h, 80 °C).…”

Interaction and Energy Decomposition Analyses to Predict Stability of Tetraaryl Square Planar Cobalt Complexes

“…[13] While this two-step process also applies to other doubly ortho-substituted arenes (i. e. 1,3-diflurorobenzene, 1,2,3-triflurorobenzene, 1,3,5triflurorobenzene, 1,3,4,5-tetraflurorobenzene and 1,2,3,4-tetraflurorobenzene), when other non-doubly F-substituted arenes in ortho position are used, such as 1,2,3,4-tetrafluorobenzene (Ar FH ), 1,3,5-trichlorobenzene (Ar Cl ), and 1,4-dibromo-2,5-difluorobenzene (Ar Br ), metalation occurs to give the relevant [NaCo(HMDS) 2 (Ar)] intermediates. These species can be isolated and characterized, [13,17] but no ligand redistribution is observed, failing to furnish square planar complexes.…”