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Hydrogen-Bridged Oligosilanylsilyl Mono- and Oligosilanylsilyl Dications.

ABSTRACT: Hydrogen-bridged oligosilanylsilyl borates 8 [B(C₆ F₅ )₄ ], 9[B(C₆ F₅ )₄ ] and diborates 10 [B(C₆ F₅ )₄ ]₂ have been prepared by hydride transfer between α-ω-dihydrido- (11) and branched tetrahydrido-oligosilanes (13) and trityl cation. The obtained cyclic intramolecularly stabilized silylium ions 8, 9 and bissilylium ion 10 were characterized by low temperature NMR spectroscopy supported by the results of density functional calculations. The branched Si-H-Si monocation 9 undergoes at low temperatures a fast degenerate rearrangement, which exchanges the Si-H groups with a barrier of 31 kJ mol^-1 via an antarafacial transition state. Reaction of the branched monocation 9 with a second equivalent of trityl cation or of the branched oligosilane 13 with two equivalents of trityl cation, gives at -80 °C the corresponding bissilylium ion 10, an example for a new class of highly reactive poly-Lewis acids.

SUBMITTER: Nimoth JP

PROVIDER: S-EPMC9305540 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Crystal structure of a mono-bridged calix[4]arene.

Project description:The title compound, 5(2)-[(5-bromo-pent-yl)-oxy]-1(2),1(14),3(5),5(5)-tetra-tert-butyl-1(7),1(8),1(9),1(10)-tetra-hydro-1(6) H,1(16) H-1(4,12)-dibenzo[b,e][1,7]dioxa-cyclo-dodecina-3,5(1,3)-dibenzena-cyclo-hexa-phan-3(2)-ol, C54H73BrO4, was synthesized from the reaction of tert-butyl-calix[4]arene with 1,5-di-bromo-pentane using K2CO3 in CH3CN. The structure consists of a calixarene unit with a five-carbon bridge connecting two proximal phenolic O atoms, and with a bromo-pent-oxy chain on one of the remaining phenolic O atoms. The calixarene unit was found to have a flattened cone conformation with no solvent (or other guest) mol-ecule observed in the cavity. Two of the opposite phenyl rings lean outwards with fold angles of 136.2 (1) and 133.0 (1)° between the rings and the plane of the bridging methyl-ene C atoms, while the other two opposite rings form fold angles of 83.27 (9) and 105.46 (9)°. There is considerable disorder in this mol-ecule. One of the tert-butyl groups is disordered over two conformations with occupancies of 0.527 (5) and 0.473 (5). The bromo-pent-oxy chain is disordered over three configurations with occupancies of 0.418, 0.332 and 0.250. The five-carbon bridge connecting two proximal phenolic O atoms is disordered over two conformations with occupancies of 0.537 (7) and 0.463 (7).

| S-EPMC4518971 | biostudies-literature

Stepwise isolation of low-valent, low-coordinate Sn and Pb mono- and dications in the coordination sphere of platinum.

Project description:Synthetic access to low-coordinate Pb mono- and dications is in general impeded due to their poor solubility and highly electrophilic nature. However, the electrophilicity of these cations can be tamed by attaching them to electron-rich transition metals. Following this principle we have isolated low-valent Pb mono- ([(Cy3P)2Pt-PbCl]2[AlCl4]2, 8a) and dications ([(Cy3P)2Pt(Pb)][AlCl4]2, 11) in the coordination sphere of platinum. The same approach then has been implemented for the isolation of analogous low-valent Sn mono- (7a) and dications (10). An energy decomposition analysis (EDA-NOCV) was performed to investigate the nature of Pt-Pb and Pb-Cl bonding in [(Cy3P)2Pt(PbCl2)] (2), 8a and 11. The results show that the Pt-Pb bonds in 8a and 11 are electron-sharing in nature, whereas that of the precursor 2 is a dative bond. The breakdown of attractive interactions in 2, 8a and 11 reveals that the ionic interactions in the analyzed Pt-Pb and Pb-Cl bonds are always stronger than the covalent interactions, except for the Pb-Cl bond in 8a. The calculated D3 dispersion energies show that dispersion interactions play a key role in the thermodynamic stability of 2, 8a and 11.

| S-EPMC5587986 | biostudies-literature

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| S-EPMC3662401 | biostudies-literature

Synthesis and Reactivity of the First Isolated Hydrogen-Bridged Silanol-Silanolate Anions.

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| S-EPMC7154667 | biostudies-literature

Synthesis of Mono- and Bisperoxide-Bridged Artemisinin Dimers to Elucidate the Contribution of Dimerization to Antimalarial Activity.

Project description:During the past decade, artemisinin as an antimalarial has been in the spotlight, in part due to the Nobel Prize in Physiology or Medicine awarded to Tu Youyou. While many studies have been completed detailing the significant increase in activity resulting from the dimerization of natural product artemisinin, activity increases unaccounted for by the peroxide bridge have yet to be researched. Here we outline the synthesis and testing for antimalarial activity of artemisinin dimers in which the peroxide bridge in one-half of the dimer is reduced, resulting in a dimer with one active and one deactivated artemisinin moiety.

| S-EPMC9247344 | biostudies-literature

Crystalline Divinyldiarsene Radical Cations and Dications.

Project description:The divinyldiarsene radical cations [{(NHC)C(Ph)}As]2 (GaCl4 ) (NHC=IPr: C{(NDipp)CH}2 3; SIPr: C{(NDipp)CH2 }2 4; Dipp=2,6-iPr2 C6 H3 ) and dications [{(NHC)C(Ph)}As]2 (GaCl4 )2 (NHC=IPr 5; SIPr 6) are readily accessible as crystalline solids on sequential one-electron oxidation of the corresponding divinyldiarsenes [{(NHC)C(Ph)}As]2 (NHC=IPr 1; SIPr 2) with GaCl3 . Compounds 3-6 have been characterized by X-ray diffraction, cyclic voltammetry, EPR/NMR spectroscopy, and UV/vis absorption spectroscopy as well as DFT calculations. The sequential removal of one electron from the HOMO, that is mainly the As-As ?-bond, of 1 and 2 leads to successive elongation of the As=As bond and contraction of the C-As bonds from 1/2?3/4?5/6. The UV/vis spectrum of 3 and 4 each exhibits a strong absorption in the visible region associated with SOMO-related transitions. The EPR spectrum of 3 and 4 each shows a broadened septet owing to coupling of the unpaired electron with two 75 As (I=3/2) nuclei.

| S-EPMC6899687 | biostudies-literature

Amidine dications: isolation and [Fe]-hydrogenase-related hydrogenation.

Project description:This communication demonstrates the preparation, isolation, and full characterization of superelectrophilic salts based on amidine dications in organic solvent, as their triflate salts. These dications are highly activated toward regiospecific reaction with hydrogen gas under mild conditions in the presence of a metal catalyst (Pd/C), mimicking the behavior of the natural substrate, N(5),N(10)-methenyltetrahydromethanopterin, in the iron-sulfur cluster-free [Fe]-hydrogenase.

| S-EPMC3662400 | biostudies-literature

Accumulation of lipophilic dications by mitochondria and cells.

Project description:Lipophilic monocations can pass through phospholipid bilayers and accumulate in negatively-charged compartments such as the mitochondrial matrix, driven by the membrane potential. This property is used to visualize mitochondria, to deliver therapeutic molecules to mitochondria and to measure the membrane potential. In theory, lipophilic dications have a number of advantages over monocations for these tasks, as the double charge should lead to a far greater and more selective uptake by mitochondria, increasing their therapeutic potential. However, the double charge might also limit the movement of lipophilic dications through phospholipid bilayers and little is known about their interaction with mitochondria. To see whether lipophilic dications could be taken up by mitochondria and cells, we made a series of bistriphenylphosphonium cations comprising two triphenylphosphonium moieties linked by a 2-, 4-, 5-, 6- or 10-carbon methylene bridge. The 5-, 6- and 10-carbon dications were taken up by energized mitochondria, whereas the 2- and 4-carbon dications were not. The accumulation of the dication was greater than that of the monocation methyltriphenylphosphonium. However, the uptake of dications was only described by the Nernst equation at low levels of accumulation, and beyond a threshold membrane potential of 90-100 mV there was negligible increase in dication uptake. Interestingly, the 5- and 6-carbon dications were not accumulated by cells, due to lack of permeation through the plasma membrane. These findings indicate that conjugating compounds to dications offers only a minor increase over monocations in delivery to mitochondria. Instead, this suggests that it may be possible to form dications within mitochondria that then remain within the cell.

| S-EPMC1635440 | biostudies-literature

2-(Tri-methyl-aza-nium-yl)ethyl hydrogen phosphate (phospho-choline) mono-hydrate.

Project description:In the crystal structure of the title compound, C5H14NO4P·H2O, the zwitterionic phospho-choline mol-ecules are connected by an O-H?O hydrogen bond between the phosphate groups, forming a zigzag chain along the b-axis direction. The chains are further connected through O-H?O hydrogen bonds involving water mol-ecules, forming a layer parallel to (101). Three and one C-H?O inter-actions are also observed in the layer and between the layers, respectively. The conformation of the N-C-C-O backbone is gauche with a torsion angle of -75.8?(2)°

| S-EPMC4011268 | biostudies-other

A one-dimensional iodido-bridged PtII/PtIV mixed-valence complex cation with a hydrogen sulfate counter-anion.

Project description:The title compound, catena-poly[[[bis-(ethyl-enedi-amine-?2 N,N')platinum(II)]-?-iodido-[bis-(ethyl-enedi-amine-?2 N,N')platinum(IV)]-?-iodido] tetra-(hydrogen sulfate) dihydrate], {[PtII(C2H8N2)2][PtIVI2(C2H8N2)2](HSO4)4·2H2O} n , has a linear chain structure comprising alternating platinum cations with mixed-valent oxidation states of +II/IV. Square-planar [Pt(en)2]2+ cations and elongated octa-hedral trans-[PtI2(en)2]2+ cations (en is ethyl-enedi-amine) are stacked alternately parallel to the b axis, and are bridged by the I ligands. The Pt site of the [PtII/IV(en)2] units is located on a twofold rotation axis. The I site, which is located on the same twofold rotation axis, is equally disordered over two positions. The Pt and I sites form a straight ?I-PtIV-I?PtII? chain, with PtIV-I bond lengths of 2.7202?(6) and 2.6917?(6)?Å, and PtII?I contacts of 3.2249?(6) and 3.2534?(6)?Å. The mixed-valence state of the Pt site is expressed by the structural parameter ? = (PtIV-I)/(PtII?I), with values of 0.843 and 0.827 for the two independent I atoms. In the crystal structure, the cationic columnar structure is stabilized by hydrogen bonds of the type N-H?O between the amine groups of the Pt complex chains and the disordered hydrogen sulfate counter anions, and between the amine groups and water mol-ecules of crystallization. In addition, O-H?O hydrogen bonds between the hydrogen sulfate anions and water mol-ecules of crystallization and between the hydrogen sulfate anions themselves consolidate the crystal packing.

| S-EPMC6281129 | biostudies-literature

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