Simple Access to the Heaviest Alkaline Earth Metal Hydride: A Strongly Reducing Hydrocarbon‐Soluble Barium Hydride Cluster

Wiesinger, Michael; Maitland, Brant; Färber, Christian; Ballmann, Gerd; Fischer, Christian; Elsen, Holger; Harder, Sjoerd

doi:10.1002/ange.201709771

Cited by 33 publications

(4 citation statements)

References 42 publications

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“…Furthermore, the observed chemical shift is in very good agreement with recent findings on a phosphate hydride ( 1 H chemical shift of 5.5 ppm) and is also in the range of chemical shifts observed in other investigations on metal hydrides . As the corresponding borate hydroxide is unknown, we have calculated the 1 H NMR shift of such a hypothetical Sr 5 (BO 3 ) 3 OH at the DFT‐PBE/USPP level of theory.…”

Section: Resultssupporting

confidence: 88%

“…Furthermore, the observed chemicals hift is in very good agreement with recent findings on ap hosphate hydride ( 1 H chemicals hift of 5.5 ppm) [14] and is also in the range of chemical shifts observedi no ther investigations on metal hydrides. [51][52][53] As the corresponding borate hydroxide is unknown,w eh ave calculated the 1 HNMR shift of such ah ypothetical Sr 5 (BO 3 ) 3 OH at the DFT-PBE/USPP level of theory.T he correspondingly expected chemical shift was at 3.9 ppm, clearly different from the chemical shift found for the hydride. For comparison, in phosphate hydroxide of the apatite family,t he 1 Hc hemical shift of the OH group is usually located at approximately À0.40 ppm.…”

Section: Hn Mr Spectroscopymentioning

confidence: 99%

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Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr₅(BO₃)₃H and Sr₅(¹¹BO₃)₃D

Wylezich

Valois

Suta

et al. 2020

Chemistry A European J

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The unprecedented borate hydride Sr5(BO3)3H and deuteride Sr5(11BO3)3D crystallizing in an apatite‐related structure are reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu2+, it shows broad‐band orange‐red emission under violet excitation owing to the 4f65d–4f7 transition of Eu2+. The observed 1H NMR chemical shift is in good agreement with previously reported 1H chemical shifts of ionic metal hydrides as well as with quantum chemical calculations and very different from 1H chemical shifts usually found for hydroxide ions in similar materials. FTIR and Raman spectroscopy of different samples containing 1H, 2H, natB, and 11B combined with calculations unambiguously prove the absence of hydroxide ions and the sole incorporation of hydride ions into the borate. The orange‐red emission obtained by doping with Eu2+ shows that the new compound class might be a promising host material for optical applications.

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Section: Resultssupporting

confidence: 88%

Section: Hn Mr Spectroscopymentioning

confidence: 99%

Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr₅(BO₃)₃H and Sr₅(¹¹BO₃)₃D

Wylezich

Valois

Suta

et al. 2020

Chemistry A European J

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“…Although the deprotonation of H 2 (p K a ≈ 49) by a stabilized amide (p K a of HN(SiMe 3 ) 2 = 25.8) is clearly contrathermodynamic, the feasibility of this reaction and the solubilization of AeH 2 salts has been explained by the exergonic aggregation of R 2 NAeH and AeH 2 species to larger clusters. Indeed, for the smaller amide ligand, well-defined [(Me 3 Si) 2 NAeH] 3 [AeH 2 ] 3 clusters (Ae = Ca, Sr) could be trapped by addition of the chelating ligand PMDTA ( N , N , N ′, N ″, N ″-pentamethyldiethylenetriamine); see Figure . Attempts to crystallize such clusters with the much bulkier N(Si i Pr 3 ) 2 ligand failed on account of the extremely good solubility of these species.…”

Section: Resultsmentioning

confidence: 99%

Hydrogen Isotope Exchange with Superbulky Alkaline Earth Metal Amide Catalysts

et al. 2020

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Heavier alkaline earth (Ae) metal amide complexes Ae(NR2)2 (Ae = Ca, Sr, Ba) were found to be highly active catalysts for hydrogen isotope exchange (HIE). The activities for D/H exchange between C6D6 and H2 strongly increase with metal size (Ca < Sr < Ba) and with amide bulk: N(SiMe3)2 < N(DIPP)(SiiPr3)< N(SiiPr3)2, DIPP = 2,6-diisopropylphenyl. At 120 °C and pressures of 10–50 bar, no hydrogenation side-products are produced, and TONs of 205 and TOFs of 268, competitive with those for precious metal catalysts, have been achieved. The reverse H/D exchange between C6H6 and D2 is even faster by a factor 1.5–2. Substrates also include a range of substituted arenes. Alkyl-substituted aromatic rings are preferably deuterated in acidic benzylic positions, and this tendency increases with the number of alkyl-substituents. Although unactivated (sp3)C–H units could not be deuterated, the (sp3)Si–H function in primary, secondary, and tertiary alkylsilanes could be converted. Two different pathways for C6H6/D2 isotope exchange have been evaluated by DFT calculations: (A) a deprotonation/protonation mechanism and (B) direct nucleophilic aromatic substitution. Although the exact nature of the catalyst(s) is unclear, the first step is the conversion of Ae(NR2)2 with D2 into R2NAeD which can aggregate to larger clusters. Energy profiles with model catalysts (iPr3Si)2NAeD and [(Me3Si)2NAeD]2 (Ae = Ca or Ba) show that the direct nucleophilic aromatic substitution is the most likely mechanism for deuteration of arenes. The key to this unusual reaction is the initial formation of a π-arene···Ae complex which is followed by the generation of an intermediate with a Meisenheimer anion. Heavier Ae metal amide complexes are, despite the lack of partially filled d-orbitals for substrate activation, potent catalysts for HIE.

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“…34 This is related to the formation of even larger hydride clusters when monodentate amido ligands are used. 35 In conclusion, our detailed study of molecular hydrides undoubtedly allows to understand the inherent properties of s-block metal cations as well as the nature of the metalhydride bond. While the application of such complexes as reagents and homogeneous catalysts has started to gain attention, whether s-block metals ever reach the activity and selectivity of transition metals remains to be seen.…”

Section: Group 1 Metal Complexesmentioning

confidence: 98%

Macrocyclic Ligands for Molecular Hydrides of s-Block Metals

Ghana

Okuda

2021

Bull. Jpn. Soc. Coord. Chem.

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■■ 1. IntroductionHydrides of s-, p-, d-and f-block metals are insoluble solid state materials. Currently, hydrides of highly electropositive metals (electronegativity < ≈ 1.6) such as MgH 2 , Ca(BH 4 ) 2 , and LaNi 5 H 6 are being considered as hydrogen storage materials to allow reversible hydrogen uptake and release. 1 Metal hydrides could also become useful as inexpensive and non-toxic precursors for homogeneous catalyst, if they can be dissolved. By introducing ligands such as CO, phosphines, and N-heterocyclic carbenes (NHCs) 2 homogeneous hydride catalyst precursors based on late transition metals such as Wilkinsonʼs catalyst became widely available. 3

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Simple Access to the Heaviest Alkaline Earth Metal Hydride: A Strongly Reducing Hydrocarbon‐Soluble Barium Hydride Cluster

Cited by 33 publications

References 42 publications

Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr₅(BO₃)₃H and Sr₅(¹¹BO₃)₃D

Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr₅(BO₃)₃H and Sr₅(¹¹BO₃)₃D

Hydrogen Isotope Exchange with Superbulky Alkaline Earth Metal Amide Catalysts

Macrocyclic Ligands for Molecular Hydrides of s-Block Metals

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Simple Access to the Heaviest Alkaline Earth Metal Hydride: A Strongly Reducing Hydrocarbon‐Soluble Barium Hydride Cluster

Cited by 33 publications

References 42 publications

Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr5(BO3)3H and Sr5(11BO3)3D

Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr5(BO3)3H and Sr5(11BO3)3D

Hydrogen Isotope Exchange with Superbulky Alkaline Earth Metal Amide Catalysts

Macrocyclic Ligands for Molecular Hydrides of s-Block Metals

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Product

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Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr₅(BO₃)₃H and Sr₅(¹¹BO₃)₃D

Borate Hydrides as a New Material Class: Structure, Computational Studies, and Spectroscopic Investigations on Sr₅(BO₃)₃H and Sr₅(¹¹BO₃)₃D