Metalloradical Cations and Dications Based on Divinyldiphosphene and Divinyldiarsene Ligands

Sharma, Mahendra K.; Rottschäfer, Dennis; Neumann, Beate; Stammler, Hans‐Georg; Danés, Sergi; Andrada, Diego M.; Gastel, Maurice van; Hinz, Alexander; Ghadwal, Rajendra S.

doi:10.1002/chem.202100213

Cited by 13 publications

(12 citation statements)

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“…A metalloradical cation based on divinyldiphosphene was reported in 2021. 116 The chemical oxidation of P-PC20 with two equivalents of GaCl 3 in CH 2 Cl 2 gave P-C20 as a violet solid (Scheme 76). The molecular structure of P-C20 shows a trans -bent geometry along the P–P bond and an η 3 -PPC coordination mode at the Fe atom.…”

Section: Group 15 Element Radicalsmentioning

confidence: 99%

Recent advances in stable main group element radicals: preparation and characterization

Feng

Tang

et al. 2022

Chem. Soc. Rev.

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Section: Group 15 Element Radicalsmentioning

confidence: 99%

Recent advances in stable main group element radicals: preparation and characterization

Feng

Tang

et al. 2022

Chem. Soc. Rev.

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“…Indeed, 6a-E was reacted with Fe 2 (CO) 9 to obtain metal complexes 17a-E (Scheme 5). 32 The E 2 C-moiety of 17a-E binds to the Fe atom in an η 3 -fashion as a four electron donor. Electron decomposition analyses (EDAs) of 17a-E suggest donor−acceptor type interactions between singlet energy species Fe(CO) 3 and 6a-E. 32 The CVs of 17a-E displayed two main redox events (E = P, E 1/2 = −0.85, +0.17 V; E = As, E 1/2 = −0.82, +0.27), which were assigned to the corresponding radical cations and dications.…”

Section: ■ Metalloradical Cations and Dicationsmentioning

confidence: 99%

“…32 The E 2 C-moiety of 17a-E binds to the Fe atom in an η 3 -fashion as a four electron donor. Electron decomposition analyses (EDAs) of 17a-E suggest donor−acceptor type interactions between singlet energy species Fe(CO) 3 and 6a-E. 32 The CVs of 17a-E displayed two main redox events (E = P, E 1/2 = −0.85, +0.17 V; E = As, E 1/2 = −0.82, +0.27), which were assigned to the corresponding radical cations and dications. Expectedly, 17a-E underwent sequential one-electron oxidation with GaCl 3 to form the radical cations 18a-E and dications 19a-E, which were isolated as crystalline solids.…”

Section: ■ Metalloradical Cations and Dicationsmentioning

confidence: 99%

“…As expected, the 31 P NMR spectrum of 19a-P displayed two doublets at +0.3 and +454.9 ppm ( 1 J PP = 352 Hz), consistent with the presence of two magnetically dissimilar phosphorus nuclei. 32 The EPR spectrum of 18a-P (Figure 11) showed a doublet of doublets because of the coupling of the unpaired electron with two magnetically inequivalent 31 P nuclei (I = 1/2).…”

Section: ■ Metalloradical Cations and Dicationsmentioning

confidence: 99%

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Tuning the Electronic Properties of Main-Group Species by N-Heterocyclic Vinyl (NHV) Scaffolds

Ghadwal

2022

Acc. Chem. Res.

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Conspectus Molecules and materials with easily tunable electronic structures and properties are at the forefront of contemporary research. π-Conjugation is fundamental in organic chemistry and plays a key role in the design of molecular materials. In this Account, we showcase the applicability of N-heterocyclic vinyl (NHV) substituents based on classical N-heterocyclic carbenes (NHCs) for tuning the structure, properties, and stability of main-group species (E) via π-conjugation and/or π-donation. NHVs such as [(NHC)CR] (R = H or aryl) are monoanionic ligands formally derived by the deprotonation of N-heterocyclic olefins (NHOs), (NHC)CHR. Further deprotonation of [(NHC)CR] (R = H) is viable, giving rise to N-heterocyclic vinylidene (NHVD) species such as (NHC)C. NHVs and NHVDs feature a highly polarizable exocyclic CNHCC bond because of the presence of adjacent π-donor nitrogen atoms. The nature of the NHC, in particular the π-acceptor property, has a direct consequence on the polarity of the CNHCC bond and hence on the magnitude of π-conjugation in the derived molecules. Thus, the electronic structure, especially the energy and shape of frontier molecular orbitals, HOMO and LUMO, of derived species can be fine-tuned by a judicious choice of the carbene unit. For instance, the HOMO of classical diphosphenes (RPPR) (R = alkyl or aryl) is invariably the phosphorus lone-pair orbital, while the PP π-bond is HOMO – 1 or HOMO – 2. In strong contrast, the HOMO of divinyldiphosphenes (R = NHV) is mainly the PP π-bond. This is owing to the π-conjugation, resulting in the lowering of the LUMO and raising of the HOMO energy. They have a remarkably small HOMO–LUMO energy gap (4.15–4.50 eV) and readily undergo 1e-oxidations, giving rise to stable radical cations and dications. By employing a similar approach, one can access divinyldiarsenes and the corresponding radical cations and dications as crystalline solids. The use of divinyldiphosphenes and divinyldiarsenes as promising ligands in the stabilization of metalloradicals has been shown. By a logical selection of singlet carbenes, stable 2-phosha-1,3-butadiene and 2-arsa-1,3-butadiene compounds, as well as related radical cations and dications, can be prepared as crystalline solids. The relevance of NHV ligands as potent π-donors has been demonstrated for the stabilization of elusive electrophilic phosphinidene and arsinidene complexes {(NHV)E}Fe(CO)4 (E = P or As). Moreover, stable singlet diradicaloid [(NHC)CP]2 and p-quinodimethane derivatives [(NHC)CP2]2 based on an NHVD framework are accessible as stable solids. In this Account, a special emphasis is given to the contributions from this laboratory. The author hopes that this Account will serve as a useful reference guide for researchers interested in studying and applying NHV and NHVD scaffolds in modern molecular chemistry and materials sciences.

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“…Since the 1980s, however, paramagnetic metal complexes began to gain significant attention due to their important role in a variety of chemical reactions. 3 − 7 For instance, paramagnetic metal intermediates of the second and third rows are involved in redox reactions, chain mechanisms, homolytic cleavage, and catalysis of C–C bond formation 3 , 8 as well as in mediating redox reactions in energy-conversion processes and in biomimetic C–H bond activation and epoxidation of hydrocarbons. 9 Their intermediacy in industrial processes such as the Wacker reaction is also well-known.…”

Section: Introductionmentioning

confidence: 99%

Carborane Stabilized “19-Electron” Molybdenum Metalloradical

et al. 2021

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Paramagnetic metal complexes gained a lot of attention due to their participation in a number of important chemical reactions. In most cases, these complexes are dominated by 17-e metalloradicals that are associatively activated with highly reactive paramagnetic 19-e species. Molybdenum paramagnetic complexes are among the most investigated ones. While some examples of persistent 17-e Mo-centered radicals have been reported, in contrast, 19-e Mo-centered radicals are illusive species and as such could rarely be detected. In this work, the photodissociation of the [Cp(CO) 3 Mo] 2 dimer ( 1 ) in the presence of phosphines was revisited. As a result, the first persistent, formally 19-e Mo radical with significant electron density on the Mo center (22%), Cp(CO) 3 Mo • PPh 2 ( o -C 2 B 10 H 11 ) ( 5b ), was generated and characterized by EPR spectroscopy and MS as well as studied by DFT calculations. The stabilization of 5b was likely achieved due to a unique electron-withdrawing effect of the o -carboranyl substituent at the phosphorus center.

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Metalloradical Cations and Dications Based on Divinyldiphosphene and Divinyldiarsene Ligands

Cited by 13 publications

References 82 publications

Recent advances in stable main group element radicals: preparation and characterization

Recent advances in stable main group element radicals: preparation and characterization

Tuning the Electronic Properties of Main-Group Species by N-Heterocyclic Vinyl (NHV) Scaffolds

Carborane Stabilized “19-Electron” Molybdenum Metalloradical

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