Although the catalytic carboxylation of unactivated alkyl electrophiles has reached remarkable levels of sophistication, the intermediacy of (phenanthroline)Ni(I)–alkyl species—complexes proposed in numerous Ni-catalyzed reductive cross-coupling reactions—has been subject to speculation. Herein we report the synthesis of such elusive (phenanthroline)Ni(I) species and their reactivity with CO 2 , allowing us to address a long-standing question related to Ni-catalyzed carboxylation reactions.

Despite the knownn ucleophilic nature of [M(CF 3 ) 2 ] À (M = Cu, Ag, Au) complexes, their participation in trifluoromethylation reactions of aryl halides remains unexplored.H ere, for the first time, selective accesst oa [Cu(CF 3 ) 2 ] À species is reported, whichi su biquitous in Cumediated trifluoromethylations, and we rationalize its complex mechanistic scenario as well as its behavior compared to its silver and gold congeners through ac ombination of experimental and computational approaches.Undoubtedly, over the past years, trifluoromethyl organometallic compounds of coinage metalsh ave played ak ey role as reactive intermediates in organic synthesis. [1][2][3] In this context, fundamental studies on the reactivity of ate-type complexes as nucleophiles has received little attentionb ecause, until recently,o nly well-defined( Cat)[Au(CF 3 ) 2 ]c omplexes were isolable. [4] In 2018, we reported, for the first time, not only the isolation of au nique silver salt, (Cs)[Ag(CF 3 ) 2 ], but also its high efficiency as at ransmetalating reagent in Pd-catalyzed trifluoromethylations. [2d] Although differentl iterature reports have proposed the existence and involvemento fn ucleophilic[ Cu(CF 3 ) 2 ] À species in CÀCF 3 bond-forming reactions, their detailedc hemical behavior remains obscure. [3, 5] This can be attributed to challenges associatedw ith their selectivea ccess, their inherent instabilityand the existence of different neutraland ionic species in solution that are in equilibrium ( Figure 1).As part of our ongoing interest in the reactivity of ate-type complexes,w ew ondered whether it could be possible to unravel the potential of (Cat)[M(CF 3 ) 2 ]( M= Cu, Ag, Au) as reactive species in trifluoromethylation reactions and to compare/understandt heir performance. Herein, we explorep reviously inaccessible features of these rather unique [M(CF 3 ) 2 ] À species, including:i )adirect synthetic route fora ccessing unprecedented (Cs)[M(CF 3 ) 2 ]( M = Cu, Au) salts and their unambiguously characterization by single-crystal X-ray diffraction;i i) ac omprehensive experimental and computationala nalysis of coinage [M(CF 3 ) 2 ] À andt heir relative reactivity to ab enchmark aryl halide;a nd iii)the first experimentale vidence of the participation of [Cu(CF 3 ) 2 ] À in trifluoromethylation processes.Inspired by our previous results, we started our investigations by targeting access to (Cs)[M(CF 3 ) 2 ]( 1 M ,M= Cu, Au) using 1 Ag as aCF 3 shuttle. [2d] Gratifyingly,wewereable to in situ generate 1 Cu in quantitative yield using 1equiv of CuI and 1equiv of 1 Ag in THF or DMF at room temperature after one hour( reaction 1). [6] Although 1 Cu is insufficiently stable for isolation, [7] we confirmed its structure by using 19 FNMR spectroscopy,E SI-MS and single-crystal X-ray diffraction. [8] Thisr esult is certainly remarkable in view of the previously described difficulties to access to [Cu(CF 3 ) 2 ] À species in as electivem anner in solution. Underi dentical conditions, the reactionb etween 1 Ag and [AuCl(SMe...

Herein, we disclose the synthesis of metallacyclic Cp*CoIII complexes containing weakly chelating functional groups. We have employed these compounds not only as an exceptional platform for accessing some of the most widely invoked transient intermediates in C−H functionalization processes but also as competent catalysts in different Cp*Co‐catalyzed transformations, including a benchmark coupling reaction.

Although the catalytic carboxylation of unactivated alkyl electrophiles has reached remarkable levels of sophistication, the intermediacy of (phenanthroline)Ni(I)-alkyl species – complexes proposed in numerous Ni-catalyzed reductive cross-coupling reactions – has been subject to speculation. Herein, we report the synthesis of such elusive (phenanthroline)Ni(I) species and their reactivity with CO2, allowing us to address a long-standing challenge related to metal-catalyzed carboxylation reactions. <div> </div>