Transition Metal Mediated C–H Activation and Functionalization: The Role of Poly(pyrazolyl)borate and Poly(pyrazolyl)alkane Ligands

McKeown, Bradley A.; Lee, John P.; Mei, Jiajun; Cundari, Thomas R.; Gunnoe, T. Brent

doi:10.1002/ejic.201501470

Cited by 22 publications

(43 citation statements)

References 168 publications

(244 reference statements)

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“…24 In the context of the theoretical shifts we have repeated this work. The 1 H (Figure SI10) and 13 C NMR (Figure SI12) spectra near room temperature show the mean signals of rapid spin interconversion. The temperature series of the Tp2Fe proton shifts was calculated theoretically for the pure S = 2 state and measured experimentally (Figure 6).…”

Section: Theoretical and Computational Backgroundmentioning

confidence: 99%

“…magnets. 10,11,12 Other promising application fields of pyrazolylborate complexes are catalysis 13,14,15,16,17 and the incorporation into polymers, 18 dendrimers, 19 molecular machines, 20 and metal-organic frameworks. 21 From the very first, these compounds have been studied by using paramagnetic NMR spectroscopy (pNMR) 1,22,23,24 and the initial results have been compiled.…”

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confidence: 99%

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Paramagnetic Pyrazolylborate Complexes Tp₂M and Tp*₂M: ¹H, ¹³C, ¹¹B, and ¹⁴N NMR Spectra and First-Principles Studies of Chemical Shifts

et al. 2020

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Paramagnetic pyrazolylborates Tp2M and Tp*2M (M = Cu, Ni, Co, Fe, Mn, Cr, V) as well as [Tp2M] + and [Tp*2M] +(M = Fe, Cr, V) have been synthesized and their NMR spectra recorded. The 1 H signal shift ranges vary from ~30 ppm [Cu(II) and V(III)] to ~220 ppm [Co(II)] and the 13 C signal shift ranges from ~180 ppm [Fe(III)] to ~1150 ppm [Cr(II)]. The 11 B and 14 N shifts are ~360 ppm and ~730 ppm, respectively. Both negative and positive shifts have been observed for all nuclei. The narrow NMR signals of the Co(II), Fe(II), Fe(III), and V(III) derivatives provide resolved 13 C, 1 H couplings. All chemical shifts have been calculated from first-principles calculations on a modern version of Kurland-McGarvey theory which includes optimized structures, zero-field splittingand g-tensors, as well as signal shift contributions. Temperature dependence in the Fe(II) spin-crossover complex results from the equilibrium of the ground singlet and the excited quintet. We illustrate both the assignment and analysis capabilities, as well as the shortcomings of the current computational methodology. magnets. 10,11,12 Other promising application fields of pyrazolylborate complexes are catalysis 13,14,15,16,17 and the incorporation into polymers, 18 dendrimers, 19 molecular machines, 20 and metal-organic frameworks. 21 From the very first, these compounds have been studied by using paramagnetic NMR spectroscopy (pNMR) 1,22,23,24 and the initial results have been compiled. 25 Note that in the early literature the signs of pNMR signal shifts are inverted. Subsequent work, which shall be referred to below, is based on those findings and usually limited to proton NMR of Fe(II), Co(II), and Ni(II) derivatives. For three Co(II) derivatives Rouf, Mareš, and Vaara have tested theoretical and computational methods of calculating molecular properties, e.g., 1 H pNMR parameters. 26 Clearly, pyrazolylborate derivatives of many other paramagnetic ions exist or are conceivable and, given the diversity of this chemistry, some general questions from a pNMR point of view emerge: Which TpM-type compounds are worth investigating? What are the most useful nuclei? At what theoretical level can the spectra be reproduced? Do the calculated signal shifts support the signal assignment and thus the determination of the molecular and electronic structure? How are the signal shifts composed? Along these lines we have studied the parent compounds (Figure 1a) Tp2M (M = Cu, Ni, Co, Fe, Mn, Cr, and V), their monocations [Tp2M] + (M = Fe, Cr, and V), the methylated analogues Tp*2M (Tp* = hydrotris(3,5-dimethylpyrazole)borate, M = Cu, Ni, Co, Fe, Mn, Cr, and V), and [Tp*2M] + (M = Fe, Cr, and V). The present paper reports the 1 H, 13 C, 11 B, and 14 N NMR spectral data and their theoretical interpretation. To this end, first-principles calculations according to the recently redressed version 27,28 of the Kurland-McGarvey theory 29 have been carried out. These computations provide the respective overall pNMR signal shifts and their tensorial components, as well as co...

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confidence: 99%

Paramagnetic Pyrazolylborate Complexes Tp₂M and Tp*₂M: ¹H, ¹³C, ¹¹B, and ¹⁴N NMR Spectra and First-Principles Studies of Chemical Shifts

et al. 2020

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“…Over the years, Tp x -metal complexes have been used in many catalytic transformations, [4] including the more testing functionalization of unreactive CÀHb onds. [5] These ligands have also been used to synthesize model complexes that mimic the active sites of somem etalloenzymes, [6] and to generate materials with interesting magnetic properties. [7] In the field of catalysis, andi nl ine with one of the main goals of modern synthetic chemistryf ocused on ah ighl evel of sustainability,t he recovery of the catalysta nd its reuse after each cycle still constitute am ajor challenge.…”

Section: Introductionmentioning

confidence: 99%

Trispyrazolylborate Ligands Supported on Vinyl Addition Polynorbornenes and Their Copper Derivatives as Recyclable Catalysts

Torre

Pérez-Ortega

Beltrán

et al. 2018

Chemistry A European J

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Polynorbornenes prepared by vinyl addition polymerization and bearing pendant alkenyl groups serve as skeletons to support trispyrazolylborate ligands (Tp ) built at those alkenyl sites. Reaction with CuI in acetonitrile led to VA-PNB-Tp Cu(NCMe) (VA-PBN=vinyl addition polynorbornene) with a 0.8-1.4 mmol incorporation of Cu per gram of polymer. The presence of tetracoordinated copper(I) ions was been assessed by FTIR studies on the corresponding VA-PNB-Tp Cu(CO) adducts, in agreement with those on discrete Tp Cu(CO). The new materials were employed as heterogeneous catalysts in several carbene- and nitrene-transfer reactions, showing a behavior similar to that of the homogeneous counterparts but also being recycled several times maintaining a high degree of activity and selectivity. This is the first example of supported Tp ligands onto polymeric supports with catalytic applications.

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“…Importantly, it has been shown that there is no systematic trend in comparative electron donor ability of Tp relative to Cp [39]. Their electron-donating abilities are dependent upon the identity and oxidation state of the metal center as well as the properties of the other ligands in the complex [40].…”

Section: Introductionmentioning

confidence: 99%

C-Homoscorpionate Oxidation Catalysts—Electrochemical and Catalytic Activity

Martins

2017

Catalysts

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Transition Metal Mediated C–H Activation and Functionalization: The Role of Poly(pyrazolyl)borate and Poly(pyrazolyl)alkane Ligands

Cited by 22 publications

References 168 publications

Paramagnetic Pyrazolylborate Complexes Tp₂M and Tp*₂M: ¹H, ¹³C, ¹¹B, and ¹⁴N NMR Spectra and First-Principles Studies of Chemical Shifts

Paramagnetic Pyrazolylborate Complexes Tp₂M and Tp*₂M: ¹H, ¹³C, ¹¹B, and ¹⁴N NMR Spectra and First-Principles Studies of Chemical Shifts

Trispyrazolylborate Ligands Supported on Vinyl Addition Polynorbornenes and Their Copper Derivatives as Recyclable Catalysts

C-Homoscorpionate Oxidation Catalysts—Electrochemical and Catalytic Activity

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Transition Metal Mediated C–H Activation and Functionalization: The Role of Poly(pyrazolyl)borate and Poly(pyrazolyl)alkane Ligands

Cited by 22 publications

References 168 publications

Paramagnetic Pyrazolylborate Complexes Tp2M and Tp*2M: 1H, 13C, 11B, and 14N NMR Spectra and First-Principles Studies of Chemical Shifts

Paramagnetic Pyrazolylborate Complexes Tp2M and Tp*2M: 1H, 13C, 11B, and 14N NMR Spectra and First-Principles Studies of Chemical Shifts

Trispyrazolylborate Ligands Supported on Vinyl Addition Polynorbornenes and Their Copper Derivatives as Recyclable Catalysts

C-Homoscorpionate Oxidation Catalysts—Electrochemical and Catalytic Activity

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Paramagnetic Pyrazolylborate Complexes Tp₂M and Tp*₂M: ¹H, ¹³C, ¹¹B, and ¹⁴N NMR Spectra and First-Principles Studies of Chemical Shifts

Paramagnetic Pyrazolylborate Complexes Tp₂M and Tp*₂M: ¹H, ¹³C, ¹¹B, and ¹⁴N NMR Spectra and First-Principles Studies of Chemical Shifts