Molecular Weight Estimation of Molecules Incorporating Heavier Elements from van‐der‐Waals Corrected ECC‐DOSY

Kreyenschmidt, Anne-Kathrin; Bachmann, S.; Niklas, Thomas

doi:10.1002/slct.201701497

Cited by 33 publications

(29 citation statements)

References 30 publications

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“…16 Since the latter are insoluble in our case, only monomeric and homochiral dimeric complexes (both consisting only of the major enantiomer) stay in solution. This was supported by 1 H DOSY NMR experiments [24][25][26][27] of enantiopure (-)-NBE reacted with ZnMe2 in toluene-d8, which indicated that the complexes have a higher molecular weight (MW) than expected from monomeric (-)-NBE-ZnMe over a broad temperature range (cf. Supplementary Fig.…”

Section: Discussionmentioning

confidence: 85%

Hyperpositive nonlinear effects in asymmetric catalysis

Geiger¹,

Achard²,

Maisse‐François³

et al. 2020

Nat Catal

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Asymmetric amplification is a curious phenomenon which is believed to play a key role in the emergence of biological homochirality, and thus of life itself. In asymmetric catalysis, it is achieved via positive non-linear effects, which allow high product enantiomeric excesses with a non-enantiopure catalyst. However, it has also been proposed that non-enantiopure catalysts may be even more enantioselective than their enantiopure counterparts, though such a case has never been experimentally observed to date. Here we show an example of such a hyperpositive non-linear effect in asymmetric catalysis. We found that addition of dialkylzinc reagents to benzaldehyde gave higher product e.e.s with only partially resolved chiral N-benzyl-ephedrine ligands. A mechanistic study was carried out and our results point toward a two-component catalysis, where mononuclear as well as aggregated catalysts are in equilibrium and in competition. These results introduce an unprecedented class of asymmetric amplification in enantioselective catalysis.

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Section: Discussionmentioning

confidence: 85%

Hyperpositive nonlinear effects in asymmetric catalysis

Geiger¹,

Achard²,

Maisse‐François³

et al. 2020

Nat Catal

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“…Theeffect of ligand size on cluster size was investigated by DOSY NMR using the external calibration method described by Stalke and co-workers (see Supporting Information). [48] For 1-Ca and 1-Ba in benzene we found in both cases molecular weights lower than calculated for the monomers (1-Ca:c alc. 697, found 515; 1-Ba:c alc.7 95, found 548).…”

Section: Angewandte Chemiementioning

confidence: 56%

Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings

et al. 2020

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Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)2]2 (1‐Ae) and Ae[N(TRIP)(DIPP)]2 (2‐Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=SiiPr3, DIPP=2,6‐diisopropylphenyl). While monomeric 1‐Ca was already known, the new complexes have been structurally characterized. Monomers 1‐Ae are highly linear while the monomers 2‐Ae are slightly bent. The bulkier amide complexes 1‐Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1‐Ba can reduce internal alkenes like cyclohexene or 3‐hexene and highly challenging substrates like 1‐Me‐cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1‐Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi‐substituted unactivated alkenes and even to arenes among which benzene.

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“…Chemical shifts were referenced to residual protic impurities in the solvent ( 1 H) or the deuterio solvent ( 13 C) and reported relative to external SiMe 4 ( 1 H, 13 C), H 3 PO 4 ( 31 P), Me 2 Se ( 77 Se), or Me 2 Te ( 125 Te). For molecular weight estimation, external calibration curves together with a correction factor dependent on the molar density were used in the CC-MW estimation software v1.3 [ 27 , 28 ]. APCI-DIP (atmospheric pressure chemical ionization-direct inlet probe) mass determinations were performed on a Finnigan LCQ Deca ( ThermoQuest ).…”

Section: Methodsmentioning

confidence: 99%

C2-Symmetric P-Stereogenic Ferrocene Ligands with Heavier Chalcogenophosphinous Acid Ester Donor Sites

2021

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tert-Butyl-substituted diphospha[2]ferrocenophane was used as a stereochemically confined diphosphane to investigate the addition of various dichalcoganes (R2Ch2; Ch = S, Se, Te and R = Me, Ph). Bischalcogenophosphinous acid esters bearing four soft donor sides were obtained as a mixture of rac and meso diastereomers and characterized by means of multinuclear NMR and X-ray analysis. The coordination chemistry of multidentate ligand 3b was explored toward d10 coinage metal centers (Cu(I), Ag(I), and Au(I)), yielding various bimetallic complexes.

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Molecular Weight Estimation of Molecules Incorporating Heavier Elements from van‐der‐Waals Corrected ECC‐DOSY

Cited by 33 publications

References 30 publications

Hyperpositive nonlinear effects in asymmetric catalysis

Hyperpositive nonlinear effects in asymmetric catalysis

Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings

C2-Symmetric P-Stereogenic Ferrocene Ligands with Heavier Chalcogenophosphinous Acid Ester Donor Sites

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