Electrosynthesis of Rh2(dpf)4(R) where dpf = N,N′-diphenylformamidinate anion and R = CH3, C2H5, C3H7, C4H9 or C5H11

Bear, John L.; Caemelbecke, Eric Van; Ngubane, Siyabonga; Da-Riz, V.; Kadish, Karl M.

doi:10.1039/c0dt01453b

Cited by 12 publications

(8 citation statements)

References 20 publications

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“…It should be noted that literature and our previous DFT calculations suggested that dehydrate species of dirhodium complexes exhibited more anodic reduction potentials than those of dirhodium complexes with aqua ligands. The dehydrate species [2] and [3] are easily obtained by the simple drying under vacuum at 373 K and can be dissolved in CH 2 Cl 2 , remaining uncoordinated to the Rh 2 center ([1] was insoluble in CH 2 Cl 2 ).…”

Section: Resultsmentioning

confidence: 77%

“…Previous studies by Bernhard and Bokarev groups reported that the excited state of [Ir−PS‐1], i. e., *[Ir−PS‐1], could be reductively quenched by TEA, yielding [Ir−PS‐1] − , which can reduces a HEC in the course of photochemical hydrogen evolution reactions. Initially, the UV‐VIS absorption of the AP systems with [2(H 2 O) 2 ] and [3(H 2 O) 2 ] before and after 1 min of visible light irradiation were monitored.…”

Section: Resultsmentioning

confidence: 99%

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Experimental and Theoretical Study of Photochemical Hydrogen Evolution Catalyzed by Paddlewheel‐Type Dirhodium Complexes with Electron Withdrawing Carboxylate Ligands

et al. 2019

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which is the most effective hydrogen evolution catalyst (HEC) among rhodium complexes developed to date. Artificial photosynthesis (AP) systems with [2(H 2 O) 2 ] or [3(H 2 O) 2 ], [Ir(ppy) 2 (bpy)](PF 6 ), and TEA showed highly efficient hydrogen evolution activities; the turnover numbers (TON) of hydrogen evolution per Rh by the AP systems with [2(H 2 O) 2 ] and [3(H 2 O) 2 ] after 12 h of photoirradiation were 3334 and 3138, respectively. Experimental analyses and density functional theory (DFT) calculations afforded valuable insight into the hydrogen evolution mechanism of paddlewheel-type dirhodium complexes; (i) hydrogen evolution activities of the AP systems with [2(H 2 O) 2 ] and [3(H 2 O) 2 ] were slightly lower than that of the AP system with [1(H 2 O) 2 ] despite one-electron reduction potentials of [2(H 2 O) 2 ] and [3(H 2 O) 2 ] lie on the anode side than that of [1(H 2 O) 2 ], and (ii) two different pathways exist during the early stages in the photochemical hydrogen evolution by [2(H 2 O) 2 ] and [3(H 2 O) 2 ]. Moreover, the relative free-energy diagrams estimated by DFT calculations clarified the energy profiles of the mechanism including the rate-determining steps of the hydrogen evolution by [1(H 2 O) 2 ]À [3(H 2 O) 2 ]. ns. The laser pulse, the flash lamp, and the gate of the ICCD was synchronized using a digital pulse generator (DG535, Stanford Research Systems).

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Section: Resultsmentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Experimental and Theoretical Study of Photochemical Hydrogen Evolution Catalyzed by Paddlewheel‐Type Dirhodium Complexes with Electron Withdrawing Carboxylate Ligands

et al. 2019

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“…Results obtained with respect to reduction potentials show near- and quasi-reversible Rh 2 4+ to Rh 2 3+ reduction potentials for C3 , C5 , and C6 . The quasi-reversibility is attributed to reaction of the reduced species with the solvent (CH 2 Cl 2 ) to produce a Rh-carbon bond species, similar to that reported by Bear et al Complex C4 exhibits an irreversible reduction at −1.63 V, possibly masked in true nature due the proposed reaction with the CH 2 Cl 2 occurring faster at the 100 mV/s scan rate for this complex. The half-wave potential for compound C6 (−1.18 V) is notably lower than that of compound C3 (−1.34 V).…”

Section: Resultsmentioning

confidence: 99%

Bimetallic Paddlewheel-type Dirhodium(II,II) Acetate and Formamidinate Complexes: Synthesis, Structure, Electrochemistry, and Hydroformylation Activity

et al. 2020

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Classical hydroformylation catalysts use mononuclear rhodium(I) complexes as precursors; however, very few examples of bimetallic systems have been reported. Herein, we report fully substituted dirhodium(II,II) complexes (C1−C6) containing acetate and diphenylformamidinate bridging ligands (L1−L4). The structure and geometry around these paddlewheeltype, bimetallic cores were confirmed by single-crystal X-ray diffraction. The complexes C3−C6 show electrochemical redox reactions, with the expected reduction (Rh 2 4+/3+ ) and two oxidation (Rh 2 4+/5+ and Rh 2 5+/6+ ) electron transfer processes. Furthermore, the bimetallic complexes were evaluated as catalyst precursors for the hydroformylation of 1-octene, with the acetate-containing complexes (C1 and C2) showing near quantitative conversion (>99%) of 1-octene, excellent activity and chemoselectivity toward aldehydes (>98%), with moderate regioselectivity toward linear products. Replacement of the acetate with diphenylformamidinate ligands (complexes C3−C6) yielded moderate-togood chemoselectivity and regioselectivity, favoring linear aldehydes.

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“…The rhodium amidinate dimers possess three reversible or quasi-reversible metal-based single-electron redox couples, corresponding to two oxidations and one reduction, as seen in Figure for complex 1 . − ,,,,, The redox processes should have a positive trend relative to the Hammett parameter (σ), since a higher positive σ correlates with a stronger electron withdrawing group on the ligand, making the coordinated metal harder to oxidize and easier to reduce. This trend has been observed in the literature for the pendant aryl groups of metal amidinates , and can be seen passing from 8 to 7 to 6 in Figure (top) (see also Table S29 of the Supporting Information for 1 to 4 ).…”

Section: Resultsmentioning

confidence: 99%

Optoelectronic Properties and Structural Effects of the Incremental Addition of Pyridyl Moieties on a Rhodium Dimer

Chartrand

Hanan

2014

J. Phys. Chem. A

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The synthesis and characterization of five C-C coupling products obtained from the reaction of a paddlewheel tetrakis 4-bromo-N,N'-diphenylbenzamidinate dirhodium dimer with 4-pyridineboronic acid pinacol ester are reported. The coupling reactions occur on one to four amidinate ligands, leading to rhodium dimers containing [tetrakis, tris, cis-bis, trans-bis, or mono]-N,N'-diphenyl-4-(pyridin-4-yl)benzamidinate ligands, effectively creating new binding sites on the metal complexes. The new compounds were isolated by column chromatography, and the exact conformations were verified by X-ray crystallography. Redox processes showed only a small variation within the coupling products and included two oxidations (1.30 ± 0.02 V, 0.27 ± 0.01 V vs SCE) and one reduction (-1.55 ± 0.02 V vs SCE), all centered on the Rh-Rh core. Time-dependent density functional theory (TD-DFT) was used to analyze this series with four other fully characterized N,N'-diphenyl-aryl-amidinate rhodium dimers that were found in the literature. The two main absorption bands of these nine rhodium dimers were compared to TD-DFT calculations, both giving excellent correlation. The first, a metal-to-metal (MM) transition around 11800 cm(-1) (845 nm) was blue-shifted in the calculation, with an average difference of 1378 cm(-1) but had only a 15 cm(-1) standard deviation, showing a strong correlation despite the energy difference. The second, a metal-to-ligand charge transfer (MLCT) transition around 18900 cm(-1) (530 nm) was a near perfect match with only a 64 cm(-1) average difference and a 35 cm(-1) standard deviation. The electronic transition, redox potentials, and HOMO and LUMO energies of all dimers were plotted versus the Hammett parameter (σ) of the aryl group and Taft's model with 2 components: field effects (σF) and resonance (σR). The properties involving only the Rh-Rh core (MM band, all oxidation potentials, HOMO and LUMO) were fit with a single set of σF and σR contributions (73% and 27%), with a goodness-of-fit (R(2)) value ranging from 90% to 99.7%. The metal-dimer to ligand charge-transfer band, involving the amidinate ligand, displayed different values of contribution with 45% and 55% for the σF and σR, respectively, with a fit of 94.8%. The accuracy of these fits enables the designed modification of amidinate-based dirhodium complexes to achieve desirable redox and spectroscopic properties.

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Electrosynthesis of Rh2(dpf)4(R) where dpf = N,N′-diphenylformamidinate anion and R = CH3, C2H5, C3H7, C4H9 or C5H11

Cited by 12 publications

References 20 publications

Experimental and Theoretical Study of Photochemical Hydrogen Evolution Catalyzed by Paddlewheel‐Type Dirhodium Complexes with Electron Withdrawing Carboxylate Ligands

Experimental and Theoretical Study of Photochemical Hydrogen Evolution Catalyzed by Paddlewheel‐Type Dirhodium Complexes with Electron Withdrawing Carboxylate Ligands

Bimetallic Paddlewheel-type Dirhodium(II,II) Acetate and Formamidinate Complexes: Synthesis, Structure, Electrochemistry, and Hydroformylation Activity

Optoelectronic Properties and Structural Effects of the Incremental Addition of Pyridyl Moieties on a Rhodium Dimer

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