Insight into trifluoromethylation – experimental electron density for Togni reagent I

Wang, Ruimin; Kalf, Irmgard; Englert, Ulli

doi:10.1039/c8ra07187j

Cited by 10 publications

(11 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The experimental quantification of intermolecular interactions involving heavier halogens like bromine and iodine is challenging due to absorption problems in the data. Even then, the experimental ED results from a laboratory X-ray data on Br•••Br [34,37], Br•••Cl [35,37] [43,44] XBs were remarkably comparable with those obtained from theoretical calculations. The true testament to the strength of halogen bonds involving bromine can be observed in the mentioned studies, where despite the lack of any strong hydrogen bond donors, the molecules crystallize as solids at room temperature, via only halogen bonding motifs.…”

Section: Halogen Bondssupporting

confidence: 69%

The Relevance of Experimental Charge Density Analysis in Unraveling Noncovalent Interactions in Molecular Crystals

et al. 2022

View full text Add to dashboard Cite

The work carried out by our research group over the last couple of decades in the context of quantitative crystal engineering involves the analysis of intermolecular interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding using experimental charge density methodology is reviewed. The focus is to extract electron density distribution in the intermolecular space and to obtain guidelines to evaluate the strength and directionality of such interactions towards the design of molecular crystals with desired properties. Following the early studies on halogen bonding interactions, several “sigma-hole” interaction types with similar electrostatic origins have been explored in recent times for their strength, origin, and structural consequences. These include interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding. Experimental X-ray charge density analysis has proved to be a powerful tool in unraveling the strength and electronic origin of such interactions, providing insights beyond the theoretical estimates from gas-phase molecular dimer calculations. In this mini-review, we outline some selected contributions from the X-ray charge density studies to the field of non-covalent interactions (NCIs) involving elements of the groups 14–17 of the periodic table. Quantitative insights into the nature of these interactions obtained from the experimental electron density distribution and subsequent topological analysis by the quantum theory of atoms in molecules (QTAIM) have been discussed. A few notable examples of weak interactions have been presented in terms of their experimental charge density features. These examples reveal not only the strength and beauty of X-ray charge density multipole modeling as an advanced structural chemistry tool but also its utility in providing experimental benchmarks for the theoretical studies of weak interactions in crystals.

show abstract

Section: Halogen Bondssupporting

confidence: 69%

The Relevance of Experimental Charge Density Analysis in Unraveling Noncovalent Interactions in Molecular Crystals

et al. 2022

View full text Add to dashboard Cite

show abstract

“…molecular OÁ Á ÁI contacts of 2.9822 (9) Å in the solid state. Our high-resolution diffraction experiment (Wang et al, 2018b) confirmed predictions concerning the hole (Kirshenboim & Kozuch, 2016) and the approach of a nucleophile as an important step in the suggested mechanism (Sala et al, 2014(Sala et al, , 2015. 70 years after Archer's observation (Archer, 1948) of short IÁ Á ÁO contacts between neighbouring iodoxy groups, our bona fide first experimental charge density for a hypervalent iodine derivative provided crystallographic evidence for the charge distribution about the halogen bond behind these interactions.…”

Section: Results For Iá á áN and Iá á áO Halogen Bondssupporting

confidence: 76%

The many flavours of halogen bonds – message from experimental electron density and Raman spectroscopy

Wang

George²,

Potts

et al. 2019

Acta Crystallogr C Struct Chem

Self Cite

View full text Add to dashboard Cite

Experimental electron-density studies based on high-resolution diffraction experiments allow halogen bonds between heavy halogens to be classified. The topological properties of the electron density in Cl...Cl contacts vary smoothly as a function of the interaction distance. The situation is less straightforward for halogen bonds between iodine and small electronegative nucleophiles, such as nitrogen or oxygen, where the electron density in the bond critical point does not simply increase for shorter distances. The number of successful charge–density studies involving iodine is small, but at least individual examples for three cases have been observed. (a) Very short halogen bonds between electron-rich nucleophiles and heavy halogen atoms resemble three-centre–four-electron bonds, with a rather symmetric heavy halogen and without an appreciable σ hole. (b) For a narrow intermediate range of halogen bonds, the asymmetric electronic situation for the heavy halogen with a pronounced σ hole leads to rather low electron density in the (3,−1) critical point of the halogen bond; the properties of this bond critical point cannot fully describe the nature of the associated interaction. (c) For longer and presumably weaker contacts, the electron density in the halogen bond critical point is only to a minor extent reduced by the presence of the σ hole and hence may be higher than in the aforementioned case. In addition to the electron density and its derived properties, the halogen–carbon bond distance opposite to the σ hole and the Raman frequency for the associated vibration emerge as alternative criteria to gauge the halogen-bond strength. We find exceptionally long C—I distances for tetrafluorodiiodobenzene molecules in cocrystals with short halogen bonds and a significant red shift for their Raman vibrations.

show abstract

“…XB acceptors. X-ray diffraction has provided information beyond geometry and confirmed the -hole model from theory: experimental charge-density studies based on high-resolution diffraction data have provided insight into the nature of strong (Bianchi et al, 2003(Bianchi et al, , 2004Wang et al, 2012Wang et al, , 2018aWang et al, , 2019 and weak (Otte et al, 2021) XBs, and even for hypervalent iodine compounds, such as Togni reagent I (Wang et al, 2018b). The above-mentioned linkers in crystal engineering, our ditopic molecules, not only act as Lewis bases towards metal cations but can also engage in halogen bonds as nucleophiles (Merkens et al, 2013) and as Brønsted bases towards mineral acids.…”

Section: Introductionmentioning

confidence: 88%

Weaving a 2D net of hydrogen and halogen bonds: cocrystal of a pyrazolium bromide with tetrafluorodiiodobenzene

Terwingen¹,

Ebel²,

Wang³

et al. 2022

Acta Crystallogr C

Self Cite

View full text Add to dashboard Cite

Hydrohalides of Lewis bases may act as halogen bond (XB) acceptors and combine two directional interactions, namely, hydrogen bonds (HB) and XBs in the same solid. 3-(1,3,5-Trimethyl-1H-pyrazol-4-yl)acetylacetone (C11H16N2O2, HacacMePz) was protonated with HX (X = Cl or Br) to afford the hydrohalides, C11H17N2O2 +·X − or H2acacMePz+·X − (1, X = Cl; 2, X = Br). Hydrohalides 1 and 2 are isomorphous and adopt a classical dipole packing. Consistent with the observation for most β-diketones, the enol form with an intramolecular HB is observed. Additional noteworthy interactions are HBs of the protonated pyrazolium towards the X − anion at donor–acceptor distances of 2.9671 (17) Å for 1 and 3.159 (4) Å for 2. Cocrystallization of hydrobromide 2 with the XB donor tetrafluorodiiodobenzene (TFDIB) leads to the adduct C11H17N2O2 +·Br−·0.5C6F4I2·H2O or (H2acacMePz+·Br−)2·(H2O)2·TFDIB (3), in which the XB donor TFDIB is situated on a crystallographic centre of inversion. Classical HBs link organic cations, water molecules and Br− anions into chains along [010]. Almost orthogonal to this interaction, XBs with Br...I = 3.2956 (4) Å connect neighbouring chains along [102] into two-dimensional sheets in the (10\overline{2}) plane. Assisted by their negative charge, halide anions represent particularly good nucleophiles towards XB donors.

show abstract

Insight into trifluoromethylation – experimental electron density for Togni reagent I

Abstract: The experimentally observed electron density for the “Togni reagent” explains the interaction of the hypervalent iodine atom with a nucleophile.

Cited by 10 publications

References 43 publications

The Relevance of Experimental Charge Density Analysis in Unraveling Noncovalent Interactions in Molecular Crystals

The Relevance of Experimental Charge Density Analysis in Unraveling Noncovalent Interactions in Molecular Crystals

The many flavours of halogen bonds – message from experimental electron density and Raman spectroscopy

Weaving a 2D net of hydrogen and halogen bonds: cocrystal of a pyrazolium bromide with tetrafluorodiiodobenzene

Contact Info

Product

Resources

About