Cyclopentadienyl cobalt(III) complexes: Synthetic and catalytic chemistry

Loginov, Dmitry A.; Shul’pina, Lidia S.; Muratov, Dmitry V.; Shul’pin, Georgiy B.

doi:10.1016/j.ccr.2019.01.022

Cited by 48 publications

(18 citation statements)

References 305 publications

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“…[1c] Therefore alternative synthetic strategies are needed for new monofunctionalized rhodocenium compounds. In this context, an advantageous feature of rhodium chemistry is the much higher stability of half‐sandwich rhodium(III) halide complexes in comparison to their labile cobalt(III) analogues . As we will see in the following, these rhodium(III) species are valuable synthons for our purposes (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Rhodocenium Monocarboxylic Acid Hexafluoridophosphate and Its Derivatives: Synthesis, Spectroscopy, Structure, and Electrochemistry

et al. 2020

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As an extension of our continuing work in metallocenium chemistry, we report here on new functionalized rhodocenium salts. In contrast to isoelectronic cobaltocenium compounds, rhodium as a 4d metal allows synthetic routes via prefunctionalized cyclopentadienyl half-sandwich precursors, thereby facilitating access to monofunctionalized rhodocenium salts containing substituents comprising methyl, trimethylsilyl, carboxylate and carboxylate ester as well as amide derivatives. Synthetic aspects, scope and limitations, as well as spectroscopic ( 1 H/ 13 C-NMR, IR, HR-MS), and structural (XRD) properties IntroductionAfter almost 70 years of research in metallocene chemistry, still relatively little is known about cobaltocenium, rhodocenium and iridocenium salts that are isoelectronic and as stable and redox responsive as their ubiquitous ferrocene congeners. The main reason for the underdeveloped chemistry of these metallocenium salts is their intrinsic cationic nature, making it quite difficult to access functionalized derivatives by standard chemical reactions developed for arenes. However, in recent years [a] mers and subsequently polymerized to the corresponding sidechain functionalized redox-responsive polymers.In this contribution, we aim at developing rhodocenium chemistry a bit further, in part based on our experience in cobaltocenium chemistry, [1,2] and disclose here a first chemoselective synthesis of rhodocenium monocarboxylic acid hexafluoridophosphate which is a key synthon for other monosubstituted rhodocenium salts accessible by standard carboxylic acid reactivity. The structural, spectroscopic and electrochemical properties of these new rhodocenium derivatives are compared with those of their cobaltocenium congeners. Results and Discussion SynthesisIn general, rhodocenium chemistry is somewhat different from cobaltocenium chemistry, as is often observed when comparing the reactivities and stabilities of analogous compounds of 3d vs. 4d/5d metals in a homologous group of elements. Successful synthetic routes to cobaltocenium compounds cannot simply Scheme 1. Synthesis of compounds.

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Section: Resultsmentioning

confidence: 99%

Rhodocenium Monocarboxylic Acid Hexafluoridophosphate and Its Derivatives: Synthesis, Spectroscopy, Structure, and Electrochemistry

et al. 2020

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“…Most recently during experimentation with CpCo complexes we discovered to our big surprise that CpCo(III) complexes can also promote cyclotrimerizations without the addition of reductants [34] . CpCo(III) complexes are synthetically easily accessible and air‐stable compounds [35] . The synthesis of CpCo(III) complexes containing CO and phosphite ligands, starting conveniently from CpCo(CO) 2 ( CoCa3 ), is illustrated in Scheme 20.…”

Section: Novel Cpco‐precatalystsmentioning

confidence: 99%

Cobalt Catalysts for [2+2+2] Cycloaddition Reactions: Isolated Precatalysts and in situ Generated Catalysts

Gläsel

Baumann

Hapke

2021

The Chemical Record

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2 + 2 + 2] Cycloaddition reactions belong to the not even large class of reactions, which can be catalyzed or mediated by a significant number of different transition metals. Cobalt complexes belong to the catalysts that paved the way for the extensive use and profound mechanistic knowledge on this particular transformation. Beside the established role, cyclopentadienyl (Cp) cobalt complexes inherit in synthetic applications of the cyclotrimerization reaction, modification of the precatalysts opened up novel reactivities and versatility for such catalytic initiators. At the same time the development of in situ generated cobalt catalysts allowed the conversion of novel substrates as well as novel reaction modes to be realized. In this personal account recent developments will be presented and the possibilities of catalysts containing cobalt atoms in different oxidation states be discussed.

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“…The chemistry of CpCo(III) and Cp*Co(III) complexes (Cp = cyclopentadienyl, Cp* = pentamethylcyclopentadienyl) have gained a lot of attention during the recent decade, especially also due to their role in studying C-H functionalization reactions with respect to their capability compared to the latter group 9 metals [1]. Therefore, the chemistry of the CpCo(III) fragment came into focus from the perspective of catalysis and related organometallic chemistry [2]. Novel applications of such complexes in transformations, such as transfer hydrogenations under aerobic conditions, have been studied only recently [3].…”

Section: Introductionmentioning

confidence: 99%

CpCo(III) Precatalysts for [2+2+2] Cycloadditions

2021

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Catalysts applied in cobalt-catalyzed cyclotrimerizations reactions in general rely on the use of Co(I) precatalysts or the in situ generation of Co(I) catalysts from Co(II) sources by reduction in the presence of steering ligands, often by addition of less noble metals. In this paper, we report the synthesis and properties of novel stable CpCo(III) complexes as precatalysts and their exemplary evaluation for application in catalytic [2+2+2] cycloadditions. The role of phosphite neutral ligands, as well as iodide and cyanide as anionic ligands, on the reactivity of the complexes was evaluated. A modified one-pot approach to the synthesis of Cp ring-functionalized Cp’Co(III) complexes was developed. The investigations demonstrated that CpCo(III) complexes can be directly applied as catalysts in catalytic cyclotrimerizations of triynes without reducing agents as additives.

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Cyclopentadienyl cobalt(III) complexes: Synthetic and catalytic chemistry

Cited by 48 publications

References 305 publications

Rhodocenium Monocarboxylic Acid Hexafluoridophosphate and Its Derivatives: Synthesis, Spectroscopy, Structure, and Electrochemistry

Rhodocenium Monocarboxylic Acid Hexafluoridophosphate and Its Derivatives: Synthesis, Spectroscopy, Structure, and Electrochemistry

Cobalt Catalysts for [2+2+2] Cycloaddition Reactions: Isolated Precatalysts and in situ Generated Catalysts

CpCo(III) Precatalysts for [2+2+2] Cycloadditions

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