Graham C. Saunders

On the importance of π–π stacking and cation–anion interactions in the construction of non-centrosymmetric networks of bromide salts of imidazolium cations bearing arene and polyfluoroarene rings

The salt 1-(2,3,5,6-tetrafluoropyridyl)-3-benzylimidazolium bromide crystallizes in the non-centrosymmetric space group Pna21. The structure arises from π–π stacking between the benzyl and tetrafluoropyridyl groups of the cations and cation–bromide interactions. It is the latter that gives rise to the non-centrosymmetry.

Intramolecular Hydrogen Bonding in Substituted Aminoalcohols

The qualifying features of a hydrogen bond can be contentious, particularly where the hydrogen bond is due to a constrained intramolecular interaction. Indeed there is disagreement within the literature whether it is even possible for an intramolecular hydrogen bond to form between functional groups on adjacent carbon atoms. This work considers the nature of the intramolecular interaction between the OH (donor) and NH2 (acceptor) groups of 2-aminoethanol, with varying substitution at the OH carbon. Gas-phase vibrational spectra of 1-amino-2-methyl-2-propanol (BMAE) and 1-amino-2,2-bis(trifluoromethyl)-2-ethanol (BFMAE) were recorded using Fourier transform infrared spectroscopy and compared to literature spectra of 2-aminoethanol (AE). Based on the experimental OH-stretching frequencies, the strength of the intramolecular hydrogen bond appears to increase from AE < BMAE ≪ BFMAE. Non-covalent interaction analysis shows evidence of an intramolecular hydrogen bond in all three molecules, with the order of the strength of interaction matching that of experiment. The experimental OH-stretching vibrational frequencies were found to correlate well with the calculated kinetic energy density, suggesting that this approach can be used to estimate the strength of an intramolecular hydrogen bond.

Engineering of a polar crystal structure exclusively by π–π stacking between aryl and polyfluoroaryl groups

1-(4-Nitrilo-2,3,5,6-tetrafluorophenyl)benzimidazole crystallizes in the polar space group Cc. The structure arises from the geometry of the molecule which gives columns of π–π stacked nitrilotetrafluorophenyl and benzimidazole groups in two almost orthogonal directions.

Infinite stacking of alternating polyfluoroaryl rings and bromide anions

The crystal structure of 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide comprises columns of parallel bromotetrafluorophenyl rings with an interplanar distance of 6.936(6) A separated by bromide anions.

Combining bio- and chemo-catalysis for the conversion of bio-renewable alcohols: homogeneous iridium catalysed hydrogen transfer initiated dehydration of 1,3-propanediol to aldehydes

Combining whole cell biocatalysis and chemocatalysis in a single reaction sequence avoids unnecessary separations, and the associated waste and energy consumption. Bacterial fermentation has been employed to convert waste glycerol from biodiesel production into 1,3-propanediol. This 1,3-propanediol can be extracted selectively from the aqueous fermentation broth using ionic liquids. 1,3-Propanediol in ionic liquid solution was converted to propionaldehyde by hydrogen transfer initiated dehydration (HTID) catalysed by a Cp*IrCl2(NHC) (Cp* = pentamethylcyclopentadienyl; NHC = carbene ligand) complex. The use of an ionic liquid solvent enabled the reaction to be performed under reduced pressure, facilitating the isolation of the product, and improving the reaction selectivity. The Ir(III) catalyst in ionic liquid was found to be highly recyclable.

Crystal structure and theoretical calculations of 1-(4-trifluoromethyl-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide

The salt 1-(4-trifluoromethyl-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide [(CF3C6F4)NC3H3N(CH2Ph)]+·Br– is crystallized from methanol in the space group P-421c of the tetragonal crystal system with unit cell parameters a = b = 21.6531(3) Å, c = 8.1968(2) Å, V = 3843.13(13) Å3, Z = 8, dcalc = 1.5732 g/cm3. The structure possesses square channels with a width of ca. 5.2 Å, which accounts for 14% of the volume, and contains one methanol molecule per ion pair. The cation interacts with three bromide ions through an anion–π interaction and two C–H⋯Br– interactions. These interactions are investigated by DFT calculations.

Short Intermolecular Phosphorus…Phosphorus Distances in the Crystal Structures of Bis{Bis(Perfluoroaryl)Phosphino}Methanes

Abstract The crystal structure of bis{bis(4-trifluoromethyltetrafluorophenyl)phosphino}-methane 2 determined by single crystal X-ray diffraction comprises pairs of molecules related by an inversion center and possessing short P⋅⋅⋅P distances. The molecular structure and the structure of the pairs are similar to those in the crystal structure of bis{bis(pentafluorophenyl)-phosphino}methane, although the packing is different. Comparison with the structures of bis(diphenylphosphino)methane and bis{bis(pentafluorophenyl)phosphine}difluoromethane suggests that intramolecular C–H⋅⋅⋅F–C interactions are the most important factor in determining the presence of the short P⋅⋅⋅P distances in the crystal structures of bis(diarylphosphino)methanes. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT

Crystal structure of (η5-pentamethylcyclopentadienyl){bis(pentafluorophenyl)×thiomethylphenyl phosphine-κ2S,P)chloro-iridium(III) tetrafluoroborate

The salt (η5-pentamethylcyclopentadienyl){bis(pentafluorophenyl)thiomethylphenylphosphine-κ2S,P)chloroiridium(III) tetrafluoroborate, [(η5-C5Me5)IrCl{κ2S,P-(C6F5)2PC6H4SMe-2}]BF4, crystallizes as a conglomerate in the orthorhombic crystal system in space group P212121 with unit cell parameters a = 9.9621(9) Å, b = 16.7793(15) Å, c = 18.5040(16) Å, V = 3093.1(5) Å3, Z = 4, dcalc = 2.014 g·cm−3. The structure of the SIr, SS stereoisomer reveals three-legged piano stool geometry about Ir, with Cp*-Ir, Ir-P, Ir-S and Ir-Cl distances of 1.847(5) Å, 2.2791(14) Å, 2.3451(13) Å, and 2.3840(12) Å respectively.