Anagostic Interactions under Pressure: Attractive or Repulsive?

Scherer, Wolfgang; Dunbar, Andrew C.; Barquera‐Lozada, José Enrique; Schmitz, Dominik; Eickerling, Georg; Kratzert, Daniel; Stalke, Dietmar; Lanza, Arianna; Macchi, Piero; Casati, Nicola; Ebad-Allah, J.; Kuntscher, C. A.

doi:10.1002/anie.201410532

Cited by 90 publications

(88 citation statements)

References 35 publications

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“…This resonance has been found downfield shifted up to δ 7.09 ppm in the bowsprit isomer whereas it is observed at δ 6.03 ppm in the flagpole isomer, which could be a consequence of an anagostic interaction H···Rh with the metal centre. 45,46,47 The H···Rh distance of 2.908 Å calculated for the bowsprit isomer lies in the upper range of distances observed for anagostic interactions and is much shorter than that found in the flagpole isomer (4.142 Å). 45 Molecular models show that both stereoisomers can interconvert by inversion of the 6-membered metallacycle ring.…”

Section: Scheme 5 Synthetic Strategies Applied To the Preparation Ofmentioning

confidence: 58%

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity

et al. 2018

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A series of water-soluble zwitterionic complexes featuring a carboxylate bridge-functionalized bis-N-heterocyclic carbene ligand of formula [Cp*MCl{(MeIm)CHCOO}] and [M(diene){(MeIm)CHCOO}] (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; M = Rh, Ir; MeIm = 3-methylimidazol-2-yliden-1-yl; diene = 1,5-cyclooctadiene (cod), norbornadiene (nbd)) were prepared from the salt [(MeImH)CHCOO]Br and suitable metal precursor. The solid-state structure of both types of complexes shows a boat-shaped six-membered metallacycle derived of the κC,C' coordination mode of the bis-NHC ligand. The uncoordinated carboxylate fragment is found at the bowsprit position in the Cp*M complexes, whereas in the M(diene) complexes it is at the flagpole position of the metallacycle. The complexes [Rh(diene){(MeIm)CHCOO}] (diene = cod, nbd) exist as two conformational isomers in dichloromethane, bowsprit and flagpole, that interconvert through the boat-to-boat inversion of the metallacycle. An inversion barrier of ∼17 kcal·mol was determined by two-dimensional exchange spectroscopy NMR measurements for [Rh(cod){(MeIm)CHCOO}]. Reaction of zwitterionic Cp*M complexes with methyl triflate or tetrafluoroboric acid affords the cationic complexes [Cp*MCl{(MeIm)CHCOOMe}] or [Cp*MCl{(MeIm)CHCOOH}] (M = Rh, Ir) featuring carboxy and methoxycarbonyl functionalized methylene-bridged bis-NHC ligands, respectively. Similarly, complexes [M(diene){(MeIm)CHCOOMe}] (M = Rh, Ir) were prepared by alkylation of the corresponding zwitterionic M(diene) complexes with methyl triflate. In contrast, reaction of [Ir(cod){(MeIm)CHCOO}] with HBF·EtO (Et = ethyl), CHOTf, CHI, or I gives cationic iridium(III) octahedral complexes [IrX(cod){(MeIm)CHCOO}] (X = H, Me, or I) featuring a tripodal coordination mode of the carboxylate bridge-functionalized bis-NHC ligand. The switch from κC,C' to κC,C',O coordination of the bis-NHC ligand accompanying the oxidative addition prevents the coordination of the anions eventually formed in the process that remain as counterions.

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Section: Scheme 5 Synthetic Strategies Applied To the Preparation Ofmentioning

confidence: 58%

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity

et al. 2018

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“…Evaluating the resulting model provides access to key structural properties such as, for example, intermolecular interactions (Desiraju, 2013;Pawlę dzio et al, 2018). Furthermore, charge density investigations provide valuable insights for synthetic chemists (Stalke, 2011;Flierler & Stalke, 2012;Scherer et al, 2015;Stalke, 2016;Scherer et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Comparison of different strategies for modelling hydrogen atoms in charge density analyses

Köhler

Lübben

Krause

et al. 2019

Acta Crystallogr B Struct Sci Cryst Eng Mater

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The quality of various approximation methods for modelling anisotropic displacement parameters (ADPs) for hydrogen atoms was investigated in a comparative study. A multipole refinement was performed against highresolution single crystal X-ray data of 9-diphenylthiophosphoranylanthracene (SPAnH) and 9,10-bis-diphenylthiophosphoranylanthraceneÁtoluene (SPAnPS). Hydrogen-atom parameters and structural properties derived from our collected neutron data sets were compared with those obtained from the SHADE-server, the software APD-Toolkit based on the invariom database, the results from Hirshfeld atom refinement conducted in the OLEX2 GUI (HARt), and the results of anisotropic hydrogen refinement within XD2016. Additionally, a free refinement of H-atom positions against X-ray data was performed with fixed ADPs from various methods. The resulting C-H bond distances were compared with distances from neutron diffraction experiments and the HARt results. Surprisingly, the refinement of anisotropic hydrogen displacement parameters against the X-ray data yielded the smallest deviations from the neutron values. However, the refinement of bond-directed quadrupole parameters turned out to be vital for the quality of the resulting ADPs. In both model structures, SHADE and, to a lesser extent, APD-Toolkit showed problems in dealing with atoms bonded to carbon atoms with refined Gram-Charlier parameters for anharmonic motion. The HARt method yields the most accurate C-H bond distances compared to neutron data results. Unconstrained refinement of hydrogen atom positions using ADPs derived from all other used approximation methods showed that even with well approximated hydrogen ADPs, the resulting distances were still significantly underestimated. research papers Acta Cryst. (2019). B75, 434-441 Christian Kö hler et al. Strategies for modelling hydrogen atoms 435 research papers Acta Cryst. (2019). B75, 434-441 Christian Kö hler et al. Strategies for modelling hydrogen atoms 441

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“…Cation radii [46] Ammoniab Those s-block "agostic" interactions [49] have also been observed in alkali metal hypersilanidesb yK linkhammer [50b] and may be describeda se lectrostatic interaction of the polar Si d + À CH 3 dÀ and the M d + ÀN dÀ amide dipole. [50] This Pearson-soft methyl interaction seems to be more favourable than the additional coordination of another hard ammonia molecule.…”

Section: Cationmentioning

confidence: 99%

Introducing a Hydrogen‐Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia

Neufeld

Michel

Herbst‐Irmer

et al. 2016

Chemistry A European J

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Alkali metal 1,1,1,3,3,3-hexamethyldisilazide (MHMDSs) are one of the most utilised weakly nucleophilic Brønsted bases in synthetic chemistry and especially in natural product synthesis. Like lithium organics, they aggregate depending on the employed donor solvents. Thus, they show different reactivity and selectivity as a function of their aggregation and solvation state. To date, monomeric LiHMDS with monodentate donor bases was only characterised in solution. Since the first preparation of LiHMDS in 1959 by Wannagat and Niederprüm, all efforts to crystallise monomeric LiHMDS in the absence of chelating ligands failed. Herein, we present ammonia adducts of LiHMDS, NaHMDS, KHMDS, RbHMDS and CsHMDS with unprecedented aggregation motifs: 1) The hitherto missing monomeric key compound in the LiHMDS aggregation architectures. Monomeric crystal structures of trisolvated LiHMDS (1) and NaHMDS (2), showing unique intermolecular hydrogen bonds, 2) the unprecedented tetrasolvated KHMDS (3) and RbHMDS (4) dimers and 3) the disolvated CsHMDS (5) dimer with very close intermolecular Si-CH3 ⋅⋅⋅Cs s-block "agostic" interactions have been prepared and characterised by single-crystal X-ray structure analysis.

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Anagostic Interactions under Pressure: Attractive or Repulsive?

Cited by 90 publications

References 35 publications

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity

Comparison of different strategies for modelling hydrogen atoms in charge density analyses

Introducing a Hydrogen‐Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia

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