(Pentamethylcyclopentadienyl)cobalt(III)‐Catalyzed C–H Bond Functionalization: From Discovery to Unique Reactivity and Selectivity

Abstract

High‐valent (pentamethylcyclopentadienyl)cobalt(III) [Cp*Co(III)] catalysts were found as inexpensive alternatives to (pentamethylcyclopentadienyl)rhodium(III) [Cp*Rh(III)] catalysts in the field of C—H bond functionalization, and applied to a variety of transformations. In this review, after the discovery and early examples of Cp*Co(III)‐catalyzed C—H bond functionalization are summarized, the unique reactivity and selectivity of Cp*Co(III) and the differences between the cobalt and rhodium catalysis are intensively discussed. Such differences are assumed to be caused by the lower electronegativity, hard nature, and smaller ionic radius of cobalt.magnified image

Thiocarbonyl-enabled ferrocene C–H nitrogenation by cobalt(III) catalysis: thermal and mechanochemical

“…While major advances have been accomplished with precious 4d transition metals, recent focus has shifted towards more sustainable base metals [10–17], with considerable progress by earth-abundant cobalt catalysts [18–22]. In this context, well-defined cyclopentadienyl-derived cobalt(III) complexes have proven instrumental for enabling a wealth of C–H transformations [23–41], prominently featuring transformative C–H nitrogenations [42–43] in an atom- and step-economical fashion [44–59].…”

Comparison of the Reactivities and Selectivities of Group 9 [Cp*MIII] Catalysts in C−H Functionalization Reactions

“…[3] Recently,the use of catalyst systems that are based on abundant first-row metals has attracted intensive research interest, including in the field of CÀHf unctionalization, mainly owing to economical considerations. [6] Although [Cp*Co III ]c omplexesw ere initially scrutinized as alternatives to the predominant [Cp*Rh III ]a nd [Cp*Ir III ]c atalyst systems, various intriguing differences in reactivity and/ors electivity have been revealed between these [Cp*M III ]s ystems (M = Co, Rh, and Ir). In 2013, Matsunaga, Kanai, and co-workers reporteda ne legant example of a[ Cp*Co III ]-catalyzed CÀHc onjugate addition reaction (Scheme 2), [5] which stimulated subsequent efforts at utilizing the [Cp*Co III ]c atalysts ystem in CÀH functionalization chemistry.…”

Synthesis of Bicyclo[n.1.0]alkanes by a Cobalt‐Catalyzed Multiple C(sp3)−H Activation Strategy

“…[9][10][11][12] Daugulis and co-workers first realized that the monoanionic,b identate 8-aminoquinoline (AQ) [13] could enable the use of bench-stable cobalt(II) salts as pre-catalysts by the in situ generation of high-valent cobalt(III) species. [9][10][11][12] Daugulis and co-workers first realized that the monoanionic,b identate 8-aminoquinoline (AQ) [13] could enable the use of bench-stable cobalt(II) salts as pre-catalysts by the in situ generation of high-valent cobalt(III) species.…”