The metal–carbon multiple bond in iron(I)– and iron(II)–dibenzotetramethyltetra[14]azaannulene: carbene, carbonyl, and isocyanide derivatives

Klose, Alain; Hesschenbrouck, Joëlle; Solari, Euro; Latronico, Mario; Floriani, Carlo; Re, Nazzareno; Chiesi‐Villa, Angiola; Rizzoli, Corrado

doi:10.1016/s0022-328x(99)00354-x

Cited by 31 publications

(28 citation statements)

References 116 publications

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“…While trace oxalate formation has been observed in several electrocatalytic reduction systems, 16 well-dened homogeneous metal complexes that mediate reductive CO 2 coupling to oxalate remain rare. Evans and co-workers rst reported that Cp * 2 Sm(THF) 2 reacts with CO 2 to produce the bridging oxalate species {Cp * 2 Sm} 2 (m-kOO 0 :kOO 0 -oxalato), 9a and subsequently there have been a few reports of similar transformations at lanthanides, 9b,c copper, 10 nickel, 11 titanium, 14 and iron, 12,13 though how oxalate formation occurs in these systems is oen ill-dened. Recently, a dimeric Cu(I) complex was found to mediate the selective reduction of CO 2 to oxalate at an unusually positive potential (relative to the 1-electron reduction of CO 2 ) when run electrocatalytically.…”

Section: 5mentioning

confidence: 99%

CO2 reduction by Fe(i): solvent control of C–O cleavage versus C–C coupling

Saouma

Day

et al. 2013

Chem. Sci.

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This manuscript explores the product distribution of the reaction of carbon dioxide with reactive iron(I) complexes supported by tris(phosphino)borate ligands,Cy, Ph, i Pr, mter; mter ¼ 3,5-meta-terphenyl). Our studies reveal an interesting and unexpected role for the solvent medium with respect to the course of the CO 2 activation reaction. For instance, exposure of methylcyclohexane (MeCy) solutions of ½PhBP CH2Cy 3 FeðPR 0 3 Þ to CO 2 yields the partial decarbonylation product f½PhBP CH2Cy 3 Feg 2 ðm-OÞðm-COÞ. When the reaction is instead carried out in benzene or THF, reductive coupling of CO 2 occurs to give the bridging oxalate species f½PhBP CH2Cy 3 Feg 2 ðm-kOO 0 :kOO 0 -oxalatoÞ.Reaction studies aimed at understanding this solvent effect are presented, and suggest that the product profile is ultimately determined by the ability of the solvent to coordinate the iron center. When more sterically encumbering auxiliary ligands are employed to support the iron(I) center (i.e., [PhBP Ph 3 ] À and [PhBP iPr 3 ] À ), complete decarbonylation is observed to afford structurally unusual diiron(II) products of the type {[PhBP R 3 ]Fe} 2 (m-O). A mechanistic hypothesis that is consistent with the collection of results described is offered, and suggests that reductive coupling of CO 2 likely occurs from an electronically saturated "Fe II -CO 2 _ À " species. CH2Cy 3Feg 2 ðm-OÞðm-COÞ (2) as the major product of a partial decarbonylation reaction. A red and paramagnetic bridging

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Section: 5mentioning

confidence: 99%

CO2 reduction by Fe(i): solvent control of C–O cleavage versus C–C coupling

Saouma

Day

et al. 2013

Chem. Sci.

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“…The first Fe complex that was reported to generate oxalate, although only as a minor product, is Fe I dibenzotetramethyltetra [14]azaannulene (Figure 3B2). [28] Cu I complexes, for example, Cu(triallyl-1,4,7-triazaclycononane) (Figure 3B3) and Cu[bis(1-benzyl-1H-pyrazole)](trifluoromethanesulfonato) (Figure 3B4), [5,29] were subsequently reported that can selectively generate an oxalate-bridged complex. Later, the Peters group reported a [PhBP CH 2 Cy 3 ]Fe(PPh 3 ) complex, which is capable of reductive coupling CO 2 to oxalate in 70 % yield (Figure 3B5).…”

Section: Co 2 Activation For Thermoreductive Couplingmentioning

confidence: 99%

“…In addition to f‐block metals, transition‐metal (Cu, Fe, Ni) complexes with low metal oxidation states are also capable of activating CO 2 by internal electron transfer. The first Fe complex that was reported to generate oxalate, although only as a minor product, is Fe I dibenzotetramethyltetra[14]azaannulene (Figure 3B2) [28] . Cu I complexes, for example, Cu(triallyl‐1,4,7‐triazaclycononane) (Figure 3B3) and Cu[bis(1‐benzyl‐1 H ‐pyrazole)](trifluoromethanesulfonato) (Figure 3B4), [5, 29] were subsequently reported that can selectively generate an oxalate‐bridged complex.…”

Section: Co2 Activation For Thermoreductive Couplingmentioning

confidence: 99%

Molecular Catalysts for the Reductive Homocoupling of CO₂ towards C₂₊ Compounds

et al. 2022

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The conversion of CO2 into multicarbon (C2+) compounds by reductive homocoupling offers the possibility to transform renewable energy into chemical energy carriers and thereby create “carbon‐neutral” fuels or other valuable products. Most available studies have employed heterogeneous metallic catalysts, but the use of molecular catalysts is still underexplored. However, several studies have already demonstrated the great potential of the molecular approach, namely, the possibility to gain a deep mechanistic understanding and a more precise control of the product selectivity. This Minireview summarizes recent progress in both the thermo‐ and electrochemical reductive homocoupling of CO2 toward C2+ products mediated by molecular catalysts. In addition, reductive CO homocoupling is discussed as a model for the further conversion of intermediates obtained from CO2 reduction, which may serve as a source of inspiration for developing novel molecular catalysts in the future.

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“…We also present new results that explain in a more comprehensive way the behaviour of these copper compounds under O 2 and CO 2 .Selective reduction of carbon dioxide to C ≥2 compounds using homogeneous metal complexes is a challenging transformation. Only a limited number of examples have been reported over the past decades [1][2][3][4][5][6][7][8][9][10][11][12] . In contrast, there has been a vast increase in reported catalysts for selective CO 2 reduction to C 1 compounds [13][14][15] .…”

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confidence: 99%

Oxalate production via oxidation of ascorbate rather than reduction of carbon dioxide

et al. 2021

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In the previous publication, some of us reported the conversion of a copper(I) complex to a copper(II) oxalate complex, and claimed that this conversion involved a reduction of CO 2 to oxalate (C 2 O 4 2− ). Herein, we show that the oxalate is produced not by reduction of CO 2 , but by reaction of ascorbate with oxygen. We also present new results that explain in a more comprehensive way the behaviour of these copper compounds under O 2 and CO 2 .Selective reduction of carbon dioxide to C ≥2 compounds using homogeneous metal complexes is a challenging transformation. Only a limited number of examples have been reported over the past decades [1][2][3][4][5][6][7][8][9][10][11][12] . In contrast, there has been a vast increase in reported catalysts for selective CO 2 reduction to C 1 compounds [13][14][15] . Among the examples reported for the reductive coupling of CO 2 to oxalate is a dinuclear Cu complex introduced by some of us in 2014 (ref. 16 ). The in situ generated Cu(I) complex [Cu 2 (m-xpt) 2 ](PF 6 ) 2 (3) formed by reduction of the Cu (II) precursor (1) with sodium ascorbate generated an oxalatebridged dinuclear complex (4), proposed to occur via reductive coupling of atmospheric CO 2 (Fig. 1). Release of the oxalate by addition of mineral acids was described, potentially enabling stepwise conversion of CO 2 into oxalic acid using sodium ascorbate as a comparatively mild reductant. Interestingly, oxidation of ascorbic acid by transition metal compounds, especially those of copper, has been well-known for more than a century 17,18 . Since then, the reaction mechanisms for such oxidations have been intensely studied [18][19][20][21][22] . More specifically, oxidative degradation of ascorbic acid by (a) inorganic oxidants (sodium periodate 23 , sodium hypoiodite 24 ); (b) oxygen 25,26 ; and (c) O 2 in the presence of Gd 27,28 , Co 27 , Pd 29 , Pt 29 , Cd 30 , Fe 31 , or Cu 32 compounds is reported to yield oxalate as a degradation product (see Supplementary Fig. 21 for a typical reaction sequence).We now report that the true origin of the oxalate in the communication published in 2014 is not CO 2 , as it was described, but oxidative degradation of sodium ascorbate.

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The metal–carbon multiple bond in iron(I)– and iron(II)–dibenzotetramethyltetra[14]azaannulene: carbene, carbonyl, and isocyanide derivatives

Cited by 31 publications

References 116 publications

CO2 reduction by Fe(i): solvent control of C–O cleavage versus C–C coupling

CO2 reduction by Fe(i): solvent control of C–O cleavage versus C–C coupling

Molecular Catalysts for the Reductive Homocoupling of CO₂ towards C₂₊ Compounds

Oxalate production via oxidation of ascorbate rather than reduction of carbon dioxide

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The metal–carbon multiple bond in iron(I)– and iron(II)–dibenzotetramethyltetra[14]azaannulene: carbene, carbonyl, and isocyanide derivatives

Cited by 31 publications

References 116 publications

CO2 reduction by Fe(i): solvent control of C–O cleavage versus C–C coupling

CO2 reduction by Fe(i): solvent control of C–O cleavage versus C–C coupling

Molecular Catalysts for the Reductive Homocoupling of CO2 towards C2+ Compounds

Oxalate production via oxidation of ascorbate rather than reduction of carbon dioxide

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Molecular Catalysts for the Reductive Homocoupling of CO₂ towards C₂₊ Compounds