Synthesis and Reactivity of a Transient, Terminal Nitrido Complex of Rhodium

Scheibel, Markus G.; Wu, Yanlin; Stückl, A. Claudia; Krause, Lennard; Carl, Elena; Bruin, Bas de; Schneider, Sven

doi:10.1021/ja409764j

Cited by 123 publications

(98 citation statements)

References 37 publications

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“…A variety of different aminyl, imidyl and nitridyl complexes have been reported, many of which were simply proposed as reactive intermediates [46][47][48]. However, the number of reports of well-characterized N-centered ligand radicals that are actually being employed in catalysis and shown to be reactive intermediates is limited.…”

Section: Nitrogen-centered Radicals In Catalysismentioning

confidence: 99%

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

et al. 2015

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In the context of homogeneous catalysis, openshell systems are often quite challenging to characterize. Nuclear magnetic resonance (NMR) spectroscopy is the most frequently applied tool to characterize organometallic compounds, but NMR spectra are usually broad, difficult to interpret and often futile for the study of paramagnetic compounds. As such, electron paramagnetic resonance (EPR) has proven itself as a useful spectroscopic technique to characterize paramagnetic complexes and reactive intermediates. EPR spectroscopy is a particularly useful tool to investigate their electronic structures, which is fundamental to understand their reactivity. This paper describes some selected examples of studies where EPR spectroscopy has been useful for the characterization of open-shell organometallic complexes. The paper concentrates in particular on systems where EPR spectroscopy has proven useful to understand catalytic reaction mechanisms involving paramagnetic organometallic catalysts. The expediency of EPR spectroscopy in the study of organometallic chemistry and homogenous catalysis is contextualized in the introductory Sect. 1. Section 2 of the review focusses on examples of C-C and C-N bond formation reactions, with an emphasis on catalytic reactions where ligand/substrate non-innocence plays an important role. Both carbon and nitrogen centered radicals have been shown to play an important role in these reactions. A few selected examples of catalytic alcohol oxidation proceeding via related N-centered ligand radicals are included in this section as well. Section 3 covers examples of the use of EPR spectroscopy to study important commercial ethylene oligomerization and polymerization processes. In Sect. 4 the use of EPR spectroscopy to understand the mechanisms of Atom Transfer Radical Polymerization is discussed. While this review focusses predominantly on the application of EPR spectroscopy in mechanistic studies of C-C and C-N bond formation reactions mediated by organometallic catalysts, a few selected examples describing the application of EPR spectroscopy in other catalytic reactions such as water splitting, photo-catalysis, photo-redox-catalysis and related reactions in which metal initiated (free) radical formation plays a role are included as well. EPR spectroscopic investigation in this area of research are dominated by EPR spectroscopic studies in isotropic solution, including spin trapping experiments. These reactions are highlighted in Sect. 5. EPR spectroscopic studies have proven useful to discern the correct oxidation states of the active catalysts and also to determine the effective concentrations of the active species. EPR is definitely a spectroscopic technique that is indispensable in understanding the reactivity of paramagnetic complexes and in conjunction with other advanced techniques such as X-ray absorption spectroscopy and pulsed laser polymerization it will continue to be a very practical tool.

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Section: Nitrogen-centered Radicals In Catalysismentioning

confidence: 99%

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

et al. 2015

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“…There are only a few examples of cobalt, [111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127][128] , rhodium, [129][130][131][132][133][134][135][136][137][138] and iridium [139][140][141][142][143][144][145][146][147][148][149] dinitrogen complexes, mostly revealing N-N bond activation only to a small extent, and there is no system that supports the binding of various N x H y z-species at one scaffold. -), into neutral and dianionic dinitrogen adducts of Co (Scheme 11).…”

Section: Cobalt Rhodium and Iridiummentioning

confidence: 99%

Late Metal Scaffolds that Activate Both, Dinitrogen and Reduced Dinitrogen Species N_xH_y

Köthe

Limberg

2014

Zeitschrift anorg allge chemie

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Abstract. In the context of biological nitrogen fixation, the question whether molybdenum or iron is the site for substrate binding and reduction is still discussed controversially. Therefore, the development of relevant model compounds containing early or late transition metals is essential in understanding the nature and behavior of intermediates bound to the FeMo-cofactor. Ligated early transition metal atoms are known to strongly activate N 2 and mediate its cleavage, but the resulting complexes contain metal-nitrogen bonds, which often elude

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“…[7][8][9][10][11][12][13][14][15][16][17][18] While a few of these complexes have been isolated, they tend to be extremely reactive, and often can only be observed spectroscopically. [19][20][21][22] Nonetheless, it is clear that synthetic chemists are now beginning to identify the combination of ligand requirements and synthetic procedures that can successfully generate late-metal ligand multiple bonds.…”

Section: Introductionmentioning

confidence: 99%

“…The solution phase redox properties of 1 were investigated by cyclic voltammetry. In THF at room temperature, the cyclic voltammogram of 1 displays one quasi-reversible redox feature and one reversible redox feature, at -2.20 V and -1.38 V (vs. Fc/Fc + ), respectively (Figure 2) 19 F NMR spectra were referenced to external SiMe 4 using the residual protio solvent peaks as internal standards. IR spectra were recorded on a Nicolet 6700 FT-IR spectrometer.…”

Section: Introductionmentioning

confidence: 99%