Hydrogen atoms can be located accurately and precisely by x-ray crystallography

Woińska, Magdalena; Grabowsky, Simon; Dominiak, Paulina M.; Woźniak, Krzysztof; Jayatilaka, Dylan

doi:10.1126/sciadv.1600192

Cited by 228 publications

(216 citation statements)

References 94 publications

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“…The intramolecular hydrogen bond O1···H4 is 192 pm which is very similar to FOX-7 (3) where the intramolecular hydrogen bond length is 189 nm [107]. The C1ÀN1 bond length has been determined to d C1ÀN1 : 137.4 pm.…”

Section: Crystal and Molecular Structuresupporting

confidence: 56%

Insensitive High Explosives: III. Nitroguanidine – Synthesis – Structure – Spectroscopy – Sensitiveness

Koch¹

2019

Propellants Explo Pyrotec

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This paper reviews the production, synthesis, crystallography, particle morphology and spectroscopy of the insensitive high explosive nitroguanidine, (NGu, CH4N4O2), CAS‐No: [556‐88‐7] and its isotopologues [2D4]‐NGu and [15N4]‐NGu]. When compared with standard insensitive high explosives such as 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB), 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7) and N‐guanylurea dinitramide (FOX‐12), Nitroguanidine proves to be the least sensitive. The review gives 170 references to the public domain. For Part II see ref. [1].

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Section: Crystal and Molecular Structuresupporting

confidence: 56%

Insensitive High Explosives: III. Nitroguanidine – Synthesis – Structure – Spectroscopy – Sensitiveness

Koch¹

2019

Propellants Explo Pyrotec

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“…These two effects result in H atoms being difficult to locate and their M–H bond lengths typically being underestimated. 88 Despite these problems, laboratory X-ray analysis of high-quality small molecule metal hydride crystals routinely allows identification and refinement of H − ligand positions. In contrast, synchrotron X-ray diffraction of protein crystals can only afford H atom positions under very favorable circumstances.…”

Section: Formation and Characterization Of Metal Hydridesmentioning

confidence: 99%

Hydrogenase Enzymes and Their Synthetic Models: The Role of Metal Hydrides

et al. 2016

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Hydrogenase enzymes efficiently process H2 and protons at organometallic FeFe, NiFe, or Fe active sites. Synthetic modeling of the many H2ase states has provided insight into H2ase structure and mechanism, as well as afforded catalysts for the H2 energy vector. Particularly important are hydride-bearing states, with synthetic hydride analogues now known for each hydrogenase class. These hydrides are typically prepared by protonation of low-valent cores. Examples of FeFe and NiFe hydrides derived from H2 have also been prepared. Such chemistry is more developed than mimicry of the redox-inactive monoFe enzyme, although functional models of the latter are now emerging. Advances in physical and theoretical characterization of H2ase enzymes and synthetic models have proven key to the study of hydrides in particular, and will guide modeling efforts toward more robust and active species optimized for practical applications.

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“…Since metal–hydride distances are often underestimated by X-ray crystallography, 42 discussion of these bonds focuses on the distances calculated by DFT. Consistent with an unchanged Fe–H distance is the finding that the oxidation is localized on the Cp*Fe center, as revealed by the highly localized nature of the spin density (Figure 4).…”

Section: Resultsmentioning

confidence: 99%

Interplay between Terminal and Bridging Diiron Hydrides in Neutral and Oxidized States

Tung

Wang

et al. 2017

Organometallics

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Graphical Abstract This study describes the structural, spectroscopic, and electrochemical properties of electronically unsymmetrical diiron hydrides. The terminal hydride Cp*Fe(pdt)Fe(dppe)(CO)H ([1(t-H)]0, Cp*− = Me5C5−, pdt2− = CH2(CH2S−)2, dppe = Ph2PC2H4PPh2) was prepared by hydride reduction of [Cp*Fe(pdt)Fe(dppe)(CO)(NCMe)]+. As established by X-ray crystallography, [1(t-H)]0 features a terminal hydride ligand. Unlike previous examples of terminal diiron hydrides, [1(t-H)]0 does not isomerize to the bridging hydride [1(μ-H)]0. Oxidation of [1(t-H)]0 gives [1(t-H)]+, which was also characterized crystallographically as its BF4− salt. Density functional theory (DFT) calculations indicate that [1(t-H)]+ is best described as containing an Cp*FeIII center. In solution, [1(t-H)]+ isomerizes to [1(μ-H)]+, as anticipated by DFT. Reduction of [1(μ-H)]+ by Cp2Co afforded the diferrous bridging hydride [1(μ-H)]0. Electrochemical measurements and DFT calculations indicate that the couples [1(t-H)]+/0 and [1(μ-H)]+/0 differ by 210 mV. Qualitative measurements indicate that [1(t-H)]0 and [1(μ-H)]0 are close in free energy. Protonation of [1(t-H)]0 in MeCN solution affords H2 even with weak acids via hydride transfer. In contrast, protonation of [1(μ-H)]0 yields 0.5 equiv of H2 by a proposed protonation-induced electron transfer process. Isotopic labeling indicates that μ-H/D ligands are inert.

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Hydrogen atoms can be located accurately and precisely by x-ray crystallography

Abstract: Hydrogen atoms cannot hide from x-rays anymore but can instead be detected very reliably in routine measurements.

Cited by 228 publications

References 94 publications

Insensitive High Explosives: III. Nitroguanidine – Synthesis – Structure – Spectroscopy – Sensitiveness

Insensitive High Explosives: III. Nitroguanidine – Synthesis – Structure – Spectroscopy – Sensitiveness

Hydrogenase Enzymes and Their Synthetic Models: The Role of Metal Hydrides

Interplay between Terminal and Bridging Diiron Hydrides in Neutral and Oxidized States

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