Spectroelectrochemical (IR, UV/Vis) Determination of the Reduction Pathways for a Series of [Re(CO)3(.alpha.-diimine)L']0/+ (L' = Halide, OTf-, THF, MeCN, n-PrCN, PPh3, P(OMe)3) Complexes

Stor, G.J.; Hartl, František; Outersterp, J.W.M. van; Stufkens, Derk J.

doi:10.1021/om00003a013

Cited by 224 publications

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“…In particular, this change should affect the energy of the LUMO, the reduction potential, and catalytic activity. [23][24][25][26][27][28][29][30][31][32][33] Introducing steric bulk 23,25 to prevent unwanted reactions of the catalytic species, including dimerization as either Mn Mn, 9 or C(imino) C(imino) bound species, 21 whilst at the same time reducing the risk of increased overpotential is a challenging task. Molecular designs that allow for steric and electronic effects to be decoupled are required.…”

Section: Chartmentioning

confidence: 99%

“…The anionic pathway is broadly similar to the two-electron pathway observed for Re complexes. 20,21 In contrast, the uncommon second pathway identified using pulsed EPR studies 19 involves coordination of CO 2 to the dimer [Mn(CO) 3 (2,2 -bpy)] 2 in the presence of a Brönsted acid in a concerted oxidative addition step. This process is shown to generate a low-spin Mn II -COOH complex, from which CO is subsequently released.…”

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confidence: 99%

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Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO₂ Reduction

et al. 2016

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Manganese tricarbonyl bromide complexes incorporating IP (2-[(phenylimino)]pyridine) derivatives, [MnBr(CO) 3 (IP)], are demonstrated as a new group of catalysts for CO 2 reduction, which represent the first example of utilization of phenylimino pyridine ligands on manganese centers for this purpose. The key feature is the asymmetric structure of the redox non-innocent ligand that permits independent tuning of its steric and electronic properties. The -diimine ligands and five new Mn(I) compounds have been synthesized, isolated in high yields and fully characterized, including X-ray crystallography. Their electrochemical and electrocatalytic behavior was investigated using cyclic voltammetry and UV-vis /IR spectroelectrochemistry within an OTTLE cell. Mechanistic investigations under an inert atmosphere have revealed differences in the nature of the reduction products as a function of steric bulk of the ligand. The direct ECE (electrochemical-chemical-electrochemical) formation of a five-coordinate anion [Mn(CO) 3 (IP)] -, a product of 2-electron reduction of the parent complex, is observed in case of the bulky The interest in solar fuels in terms of both photocatalytic and electrocatalytic CO 2 reduction 1 , in the latter case utilizing sustainable electricity, has been increasing markedly in the new millennium. The recent demonstration of the electrocatalytic activity of manganese 2 analogues of the archetypal Re(I) catalysts 3,4,5,6 for CO 2 reduction has given a new impetus to research into noble-metal-free catalytic systems. [MnBr(CO) 3 ( -diimine)] complexes have been shown to outperform rhenium-based analogues with regard to CO 2 reduction under certain conditions. 7 Most notably, the presence of a Brönsted acid 7-10 appears to be a prerequisite for catalysis with a range of tricarbonyl Mndiimine complexes. Mechanistic studies 5,10 of the active 2,2 -bipyridine-based (Rbpy) manganese catalysts have shown that one-electron reduction of the parent complex [MnBr(CO) 3 (R-bpy)] precursor results in the formation of the Mn Mn dimer [Mn(CO) 3 (Rbpy)] 2 . 8,9 Notably, neither the primary reduction product [MnBr(CO) 3 (R-bpy )] nor the five-coordinate radical intermediates [Mn(CO) 3 (R-bpy)] have been detected by either UV-vis or IR spectroscopy. 2,7 Nanosecond time-resolved infrared (TRIR) studies reveal that no detectable solvent adduct is formed before the dimerization of Mn species on this timescale; instead, the five-coordinate species is observed, which rapidly dimerises. 10 For some of the Re analogues, a one-electron reduced complex, [ReCl(CO) 3 (R-bpy )] was observed by IR spectroscopy and identified by the ca. 15-20 cm -1 decrease in the (CO) energy, 11,12,13 as was the five-coordinate radical [Re(CO) 3 ( t Bubpy)] by an additional 15-20 cm -1 shift .Two mechanisms have been proposed 10,14-18 for the ultimate reduction of [Mn(CO) 3 ( -diimine)] 2 in the presence of CO 2 , which can be referred to as the anionic, and the oxidative addition 19 pathways. The anionic pathway involves reduction of ...

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Section: Chartmentioning

confidence: 99%

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confidence: 99%

Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO₂ Reduction

et al. 2016

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“…The difference density plots were drawn using the GaussView software. À that undergo slow Cl À ligand substitution by a donor solvent or dimerization [4,[30][31][32][33][34]. The reduction becomes fully reversible at low temperatures [31] where the anions are stable and can be characterized spectroscopically.…”

Section: Time-resolved Uv-vis Absorption Spectra (Ta)mentioning

confidence: 99%

Origin of electronic absorption spectra of MLCT-excited and one-electron reduced 2,2′-bipyridine and 1,10-phenanthroline complexes

Záliš

Consani

Al‐Nahhas

et al. 2011

Inorganica Chimica Acta

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, respectively. UV-Vis spectra of the reduced complexes are dominated by IL transitions, plus weaker MLCT contributions. Excited-state spectra show an intense band in the UV region of $50% IL origin mixed with LMCT (bpy, 373 nm) or MLCT (phen, 307 nm) excitations. Because of the significant IL contribution, this spectral feature is akin to the principal IL band of the anions. In contrast, the excited-state visible spectral pattern arises from predominantly LMCT transitions, any resemblance with the reduced-state visible spectra being coincidental.The Re complexes studied herein are representatives of a broad class of metal a-diimines, for which similar spectroscopic behavior can be expected.

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“…A similar difference in Lewis base coordination on descending a transition metal group in the peri-odic table is observed, for example, for the coordinatively unsaturated radicals [M(CO) 3 (α-diimine)]· (M = Mn, Re; α-diimine is, e.g., bpy, iPr-PyCa, iPr-DAB). Thus, while the unsaturated radicals [Re(CO) 3 (α-diimine)]· form at room temperature fairly stable 18e paramagnetic species [Re(CO) 3 -(α-diimine)(Sv)]· (Sv = MeCN, PrCN), [56][57][58] analogous radicals were not observed for [Mn(CO) 3 (α-diimine)]·. [59] Redox Behaviour of [Os 2 Ru(CO) 10 …”

Section: Stability Of the Photoproductsmentioning

confidence: 99%

Heterosite Effects in Novel Heteronuclear Clusters [Os₂Ru(CO)₁₁(PPh₃)] and [Os₂Ru(CO)₁₀(2‐acetylpyridine‐N‐isopropylimine)]

et al. 2005

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A new synthetic route towards the mixed-metal cluster [Os 2 -Ru(CO) 12 ] is described together with the syntheses of its PPh 3 and iPr-AcPy (iPr-AcPy = 2-acetylpyridine-N-isopropylimine) derivatives. The molecular structures of the novel clusters [Os 2 Ru(CO) 11 (PPh 3 )] and [Os 2 Ru(CO) 10 (iPr-AcPy)] were determined on the basis of crystalline solid solutions of the Os 2 Ru and corresponding Os 3 species. The structures reveal that coordination of the Lewis bases occurs exclusively at the ruthenium site of [Os 2 Ru(CO) 12 ], which is in agreement with density functional theory (DFT) calculations on several structural isomers of these compounds. According to the time-dependent DFT results, the lowest optically accessible excited state of [Os 2 Ru(CO) 10 (iPr-AcPy)] has a prevailing σ(Ru-Os2)-π*(iPr-AcPy) character, with a partial σσ*(Ru-Os2) contribution. In weakly coordinating 2-chlorobutane, the excited state has a lifetime τ = 10.4 ± 1.2 ps and produces biradicals considerably faster than observed for [Os 3 (CO) 10 (iPr-AcPy) (τ = 25.3 ± 0.7 ps). In coordinating acetonitrile, the excited state of [Os 2 Ru(CO) 10 (iPr-AcPy)] decays mono-exponentially with a lifetime τ = 2.1 ± 0.2 ps. In contrast to [Os 3 (CO) 10 (iPr-AcPy)]

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Spectroelectrochemical (IR, UV/Vis) Determination of the Reduction Pathways for a Series of [Re(CO)3(.alpha.-diimine)L']0/+ (L' = Halide, OTf-, THF, MeCN, n-PrCN, PPh3, P(OMe)3) Complexes

Abstract: Spectroelectrochemical (IR,UV/VIS) Determination of the Reduction Pathways for a Series of [Re(CO)C3(alpha-diimine)LE']E0E/E+ (LE'=Halide, Otf, THF, MeCN, n-PrCN, PPhC3C' P(OMe)C3) Complexes Stor, G.J.; Hartl, F.; van Outersterp, J.W.M.; Stufkens, D.J.

Cited by 224 publications

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Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO₂ Reduction

Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO₂ Reduction

Origin of electronic absorption spectra of MLCT-excited and one-electron reduced 2,2′-bipyridine and 1,10-phenanthroline complexes

Heterosite Effects in Novel Heteronuclear Clusters [Os₂Ru(CO)₁₁(PPh₃)] and [Os₂Ru(CO)₁₀(2‐acetylpyridine‐N‐isopropylimine)]

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Spectroelectrochemical (IR, UV/Vis) Determination of the Reduction Pathways for a Series of [Re(CO)3(.alpha.-diimine)L']0/+ (L' = Halide, OTf-, THF, MeCN, n-PrCN, PPh3, P(OMe)3) Complexes

Abstract: Spectroelectrochemical (IR,UV/VIS) Determination of the Reduction Pathways for a Series of [Re(CO)C3(alpha-diimine)LE']E0E/E+ (LE'=Halide, Otf, THF, MeCN, n-PrCN, PPhC3C' P(OMe)C3) Complexes Stor, G.J.; Hartl, F.; van Outersterp, J.W.M.; Stufkens, D.J.

Cited by 224 publications

References 0 publications

Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO2 Reduction

Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO2 Reduction

Origin of electronic absorption spectra of MLCT-excited and one-electron reduced 2,2′-bipyridine and 1,10-phenanthroline complexes

Heterosite Effects in Novel Heteronuclear Clusters [Os2Ru(CO)11(PPh3)] and [Os2Ru(CO)10(2‐acetylpyridine‐N‐isopropylimine)]

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Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO₂ Reduction

Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO₂ Reduction

Heterosite Effects in Novel Heteronuclear Clusters [Os₂Ru(CO)₁₁(PPh₃)] and [Os₂Ru(CO)₁₀(2‐acetylpyridine‐N‐isopropylimine)]