Synthesis, hydrogen bond interactions and crystal structure elucidation of some stable 2H-imidazolium salts

Reaction of 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (1) with phthalimide, quinazolinedione, thiophenole and 4-pyridinethiole led to the formation of the hydrogen-bonded salts, imidazolium phthalimide (2), imidazolium quinazolinedione (3), imidazolium thiophenolate (4) and imidazolium 4-pyridinethiolate (5), respectively, in good yield. In crystals of 2, the anion is linked to the imidazolium cation by a C–H···O hydrogen bond, while in 3 and 5 C–H···N hydrogen bonds are observed. In 4, the imidazolium ion is linked to the anion by C–H···S hydrogen bonds. In compounds 2, 3 and 5, the interionic hydrogen bonds are close to linearity, while the interionic hydrogen bond angle in 4 is 148.5(9)°.

Elimination of Interionic Hydrogen Bonding in The Imidazolium-Based Ionic Liquids

Hydrogen bonding is a phenomenon of paramount importance in room-temperature ionic liquids. The presence or absence of the hydrogen bond drastically alternates self-diffusion, shear viscosity, phase transition points, and other key properties of a pure substance. For certain applications, the presence of cation-anion hydrogen bonding is undesirable. In the present paper, we investigate perspectives of removing the hydrogen...fluorine interionic attraction in the imidazolium borates, the strongest non-covalent interaction in this type of system. Chemical modification of the tetrafluoroborate anion not only eliminates hydrogen bonding but also changes the most thermodynamically preferable orientation of the cation in the vicinity of the anion. Although the most acidic hydrogen atom of the imidazole ring remains the paramount electrophilic center of the cation, it does not engender a strong electrostatically driven coordination pattern with the properly modified anions. The reported new physical insights help compose more robust ionic liquids and tune solvation properties of the imidazolium-based RTILs.

Significance of weak interactions in imidazolium picrate ionic liquids: spectroscopic and theoretical studies for molecular level understanding

The effects of interionic hydrogen bonding and π–π stacking interactions on the physical properties of a new series of picrate anion based ionic liquids (ILs) have been investigated experimentally and theoretically.

Crystal structure of tricarbonyl(N-diphenylphosphanyl-N,N′-diisopropyl-P-phenylphosphonous diamide-κ2P,P′)cobalt(I) tetracarbonylcobaltate(−I) toluene 0.25-solvate

The asymmetric unit of the title compound, [Co(C24H30N2P2)(CO)3][Co(CO)4]·0.25C7H8, consists of two crystallographically independent cations with similar conformations, two anions, and one-half of a toluene molecule disordered about an inversion centre. In the cations, a Co/P/N/P four-membered slightly bent metallacycle is the key structural element. The pendant NH group is not coordinated to the CoIatom, which displays a distorted trigonal–bipyramidal coordination geometry. Weak interionic hydrogen bonds are observed between the NH groups and a carbonyl group of the tetrahedral [Co(CO)4]−anions.

The Hexakis(N,N'-Dimethylurea)Cobalt(Ii) Cation: A Flexible Building Block for the Construction of Hydrogen Bonded Networks

The ligand N.N'-dimethylurea (DMU) is used to propagate the octahedral coordination geom- etry of [Co(DMU)6]2+ into 1D and 2D assemblies via a combination of coordinative bonds and interionic hydrogen-bonding. Compounds [Co(DMU)6](ClO4)2 (1), [Co(DMU)6](BF4)2 (2) and [Co(DMU)6](NO3)2 (3) have been prepared from the reactions of DMU and the appropriate hydrated cobalt(II) salts in EtOH. MeCN or Me2CO (only for 1) in the presence of 2,2-di- methoxypropane. Crystal structure determinations demonstrate the existence of [Co(DMU)6]2+ cations and CIO4- , BF4- or NO3- counterions. The great stability of the [Co(DMU)6]2+ cation in the solid state is attributed to a pseudochelate effect which arises from the existence of strong intracationic N-H···O(DMU) hydrogen bonds. The [Co(DMU)6]2+ cations and counterions self- assemble to form a hydrogen-bonded ID architecture in 1, and different 2D hydrogen-bonded networks in 2 and 3. The precise nature of the resulting supramolecular structure is influenced by the nature of the counterion. Two main motifs of intermolecular (interionic) hydrogen bonds have been observed: N-H ···O(ClO4-, NO3-) or N-H ··· F(BF4-) and weak C-H F(BF4- ) or C-H-O(NO3- ) hydrogen bonds. The complexes were also characterized by vibrational spec- troscopy (IR, far-IR. low-frequency Raman). The spectroscopic data are discussed in terms of the nature of bonding and the know;n structures.

Manifestations of noncovalent interactions in the solid state. 3. X-ray crystal structures of [H4(cyclam)][FeCl5(OH2)](Cl)2 and [H4(cyclam)][CF3COO]4, two network hydrogen bonded solids

FeCl2 or FeCl3 react with cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) in an acidic medium (4 M HCl) to afford dark orange-red plates of [H4(cyclam)][FeCl5(OH2)](Cl)2 (1). 1 crystallizes in a polar space group (orthorhombic, Pc21b) with a = 10.7730(6), b = 13.3418(10), c = 14.4564(10) Å, V = 2077.84(24) Å3, and Dcalc = 1.68 g cm−3 for Z = 4. Final values of R = 0.031 and Rw = 0.034 were obtained for 1950 independent observed (I > 3σ(I)) reflections. Cyclam reacts with neat trifluoroacetic acid to afford a colourless salt, [H4(cyclam)][CF3COO]4 (2). 2 crystallizes in a centric space group (monoclinic, P21/c), with a = 8.7442(11), b = 10.5121(11), c = 15.2469(20) Å, β = 102.526(15)°, V = 1368.1(3) Å3, and Dcalc = 1.593 g cm−3 for Z = 2. Final values of R = 0.059 and Rw = 0.067 were obtained for 1336 independent observed (I > 3σ(I)) reflections. Extensive interionic hydrogen bonding between the cyclam cations, which adopt exodentate conformations, and anions results in network polymeric hydrogen bonding (1-D for 1, 2-D for 2). The networking in 1 is intrinsically polar because one chloride anion and the [FeCl5(OH2)]2− complex anion are involved in networking between the H4(cyclam)4+ cations. The implications of the crystal structures are discussed from the perspective of rational design of polar solids.

Crystal structure of diethylammonium tetrachloro(p-phenoxyphenyl)tellurate

The crystal structure of diethylammonium tetrachloro(p-phenoxyphenyl)tellurate has been determined by the heavy atom method. The crystals are monoclinic, space group C2/c, with unit cell dimensions a = 19.675(5), b = 7.634(3), c = 28.716(6) Å, β = 105.58(2)°, and Z = 8. For 2636 "observed" reflections (I > 3σ(I)), R = 0.030. The primary geometry about tellurium is based on a square pyramid with a secondary interaction on the vacant side of the tellurium coordination octahedron. The ions are apparently linked by weak interionic hydrogen bonding along the crystallographic b axis.