Abstract:Achieving
multielectron activity at first-row transition-metal
complexes has important implications for homogeneous catalysis using
earth-abundant metals. Here, we report a family of cobalt–phenylenediamide
complexes that undergo reversible 2e– oxidation
regardless of the ligand substituents, enabling unprecedented multielectron
redox tuning over 0.5 V and, in each case, affording the dicationic
Co(III)-benzoquinonediimine species. The neutral complexes are best
described as delocalized systems with π-bonding… Show more
“…This result is in stark contrast to [1-MeCN] + in which the radical spin density was calculated by DFT to be mainly centred on cobalt. 5 The 1e À reduction of 2 can also be monitored by UV-vis spectroelectrochemistry (Fig. S26b, ESI †).…”
mentioning
confidence: 99%
“…[DBT-CF 3 ] + , where [1-MeCN] 2+ may be generated from the disproportionation of [1] + . 5 To probe the possibility of radical trifluoromethylation of other organic substrates, we tested the reactivity of 1 in the presence of [DBT-CF 3 ] + and 3-methyl-1H-indole at 25 1C. Indeed, the formation of 3-methyl-2-(trifluoromethyl)-1Hindole was observed by 1 H and 19 F NMR within 20 min (Fig.…”
mentioning
confidence: 99%
“…A limited number of first-row metal complexes bearing redox-active ligands exhibit a 2e − redox couple, 4,5 for which a change in coordination geometry is often required to favour potential inversion 6 and access the multielectron pathway.…”
mentioning
confidence: 99%
“…Among these examples, we recently reported a series of cobalt complexes based on the redox-active o -phenylenediamide ligand (opda). 5 By cyclic voltammetry (CV), the isopropyl derivative, complex 1 , was shown to undergo a reversible 2e − oxidation at –0.17 V vs. Fc +/0 in MeCN, yielding the dicationic complex [1–MeCN] 2+ in which the opda ligand has been fully oxidized to the benzoquinonediimine form (bqdi; Scheme 1). This 2e − oxidation can be achieved electrochemically or by treatment of 1 with a chemical oxidant.…”
mentioning
confidence: 99%
“…The N–C phenylene bond length in 2 is 1.311(5) Å, comparable to the ligand backbone in [1–MeCN] 2+ . 5 Overall, 2 is formulated as a coordinatively saturated Co( iii ) centre with a fully oxidized bqdi ligand and anionic trifluoromethyl ligand; thus, the formation of 2 involves formal ligand-to-substrate redox transfer.…”
The reactivity of an electron-rich cobalt complex bearing an o-phenylenediamide ligand with electrophilic CF3+ and F+ sources is reported. These reactions lead to generation of the Co(III)−CF3 or Co(III)−F complex,...
“…This result is in stark contrast to [1-MeCN] + in which the radical spin density was calculated by DFT to be mainly centred on cobalt. 5 The 1e À reduction of 2 can also be monitored by UV-vis spectroelectrochemistry (Fig. S26b, ESI †).…”
mentioning
confidence: 99%
“…[DBT-CF 3 ] + , where [1-MeCN] 2+ may be generated from the disproportionation of [1] + . 5 To probe the possibility of radical trifluoromethylation of other organic substrates, we tested the reactivity of 1 in the presence of [DBT-CF 3 ] + and 3-methyl-1H-indole at 25 1C. Indeed, the formation of 3-methyl-2-(trifluoromethyl)-1Hindole was observed by 1 H and 19 F NMR within 20 min (Fig.…”
mentioning
confidence: 99%
“…A limited number of first-row metal complexes bearing redox-active ligands exhibit a 2e − redox couple, 4,5 for which a change in coordination geometry is often required to favour potential inversion 6 and access the multielectron pathway.…”
mentioning
confidence: 99%
“…Among these examples, we recently reported a series of cobalt complexes based on the redox-active o -phenylenediamide ligand (opda). 5 By cyclic voltammetry (CV), the isopropyl derivative, complex 1 , was shown to undergo a reversible 2e − oxidation at –0.17 V vs. Fc +/0 in MeCN, yielding the dicationic complex [1–MeCN] 2+ in which the opda ligand has been fully oxidized to the benzoquinonediimine form (bqdi; Scheme 1). This 2e − oxidation can be achieved electrochemically or by treatment of 1 with a chemical oxidant.…”
mentioning
confidence: 99%
“…The N–C phenylene bond length in 2 is 1.311(5) Å, comparable to the ligand backbone in [1–MeCN] 2+ . 5 Overall, 2 is formulated as a coordinatively saturated Co( iii ) centre with a fully oxidized bqdi ligand and anionic trifluoromethyl ligand; thus, the formation of 2 involves formal ligand-to-substrate redox transfer.…”
The reactivity of an electron-rich cobalt complex bearing an o-phenylenediamide ligand with electrophilic CF3+ and F+ sources is reported. These reactions lead to generation of the Co(III)−CF3 or Co(III)−F complex,...
A new series of [CoIII–CF3]n+ complexes supported by a bidentate redox-active ligand is presented. The cationic [Co–CF3]+ complex was first obtained by reacting [CpCo(tBuUreaopda)] (Cp = cyclopentadienyl, opda = o-phenylenediamide)...
This review highlights the application of redox-active ligands for achieving substrate activation and reactivity through multielectron transfer at earth-abundant transition metal complexes.
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