Oxonium ions from aqua regia: isolation by hydrogen bonding to crown ethers

Anion⋅⋅⋅Anion Coinage Bonds: The Case of Tetrachloridoaurate

Interactions in crystalline tetrachloridoaurates of acetylcholine and dimethylpropiothetine are characterized by Au⋅⋅⋅Cl and Au⋅⋅⋅O short contacts. The former interactions assemble the AuCl4 - units into supramolecular anionic polymers, while the latter interactions append the acetylcholine and propiothetine units to the polymer. The distorted octahedral geometry of the bonding pattern around the gold center is rationalized on the basis of the anisotropic distribution of the electron density, which enables gold to behave as an electrophile (π-hole coinage-bond donor). Computational studies prove that gold atoms in negatively charged species can function as acceptors of electron density. The attractive nature of the Au⋅⋅⋅Cl/O interactions described here complement the known aurophilic bonds involved in gold-centered interactions.

Sequential X-ray-Induced Single-Crystal to Single-Crystal Transformation followed by Topotactic Reduction in a Potassium Crown Ether Complex of Tetrachloroaurate(III)

During data collection, the unreported potassium crown ether salt [K(18-crown-6][AuCl₄] undergoes a sequential X-ray-induced and irreversible single-crystal to single-crystal transformation from P1̅ to C2/ c followed by a topotactic reduction to crystalline [K(18-crown-6][AuCl₂] within the same C2/ c space group.

Platinum-mediated monohydration of SO2

The monohydration of SO₂ has been achieved in solution mediated by a platinum-aquo complex.

N-Alkyl pyrrolidone ether podands as versatile alkali metal ion chelants

The highly polar nature of lactam carbonyl groups makes them potent chelators of alkali metal ions as part of a flexible podand ligand.

Interaction of hydrated protons with octyl-phenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO): NMR and theoretical study

Interaction of octyl-phenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO, the 'classical' rare metal extraction agent) with fully ionized hydrated protons (HP) was studied in acetonitrile-d(3) using (1)H, (13)C, (31)P NMR, PFG NMR and magnetic relaxation. The experimental results were confronted with high-precision ab initio DFT calculations. Relative chemical shifts of NMR signals of CMPO (0.01 mol/L) under the presence of HP in the molar ratio β = 0-2.0 mol/mol show binding between CMPO and HP. Self-diffusion measurements using (1)H PFG NMR demonstrate that larger complexes with higher content of CMPO are generally formed at β < 0.75. Analyzing the collective dependence of (13)C and (31)P NMR chemical shifts on β by the use of program LETAGROP, we obtained very good fitting for the assumed coexistence of two complexes (CMPO)(2)·HP (C(2)) and CMPO.HP (C(1)). The logarithms of the respective stabilization constants log K(i) were found to be 7.518 (C(2)) and 4.581 (C(1)). The system dynamics was studied by measuring the transverse (1)H NMR relaxation using CPMG sequence with varying delays t(p) between the π pulses in the mixtures with β = 0.4-0.8. The following exchange correlation times were obtained: τ(10) = 2.35 × 10(-5), τ(20) = 0.82 × 10(-4), τ(21) = 0.45 × 10(-3) s. The DFT calculations support the conclusion that the complexes C(1) and C(2) are the main species in the mixtures of CMPO with HP. They also agree with the NMR and FTIR observation that the main site to which H(3) O(+) is bound is the P=O group, whereas the amide group does not form a strong bond with the ion when excess water molecules are present.

2,5-Bis(pyridinium-2-yl)-3,6-bis-(2-pyrid-yl)pyrazine bis-[tetra-chlorido-aurate(III)]

In the title compound, (C(24)H(18)N(6))[AuCl(4)](2), the cation is located on an inversion center. Each of the two independent Au(III) ions lies on an inversion center and has a distorted square-planar geometry. In the crystal, inter-molecular C-H⋯Cl hydrogen bonds, π-π inter-actions [centroid-centroid distances = 3.5548 (16) and 3.7507 (16) Å] and Au⋯π inter-actions [Au⋯centroid distance = 3.6424 (10) Å] are effective in the stabilization of the structure, resulting in the formation of a supra-molecular structure. Intra-molecular N-H⋯N hydrogen bonds are present in the cation.

3-Phenyl-pyridinium tetra-chlorido-aurate(III)

In the title mol-ecular salt, (C(11)H(10)N)[AuCl(4)], the Au(III) atom adopts an almost regular square-planar coordination geometry and the dihedral angle between the aromatic rings of the 3-phenyl-pyridinium cation is 23.1 (3)°. In the crystal, the ions inter-act by way of N-H⋯Cl and C-H⋯Cl hydrogen bonds.

Bis(tribenzyl-ammonium) tetra-chloridoaurate(III) chloride

In the title compound, (C(21)H(22)N)(2)[AuCl(4)]Cl, the Au(III) atom adopts a square-planar coordination geometry defined by four chloride ions. In the crystal structure, inter-molecular N-H⋯Cl hydrogen bonds link the organic cations and the uncoordinated chloride ion.

2-[3-(2-Pyrid-yl)pyrazin-2-yl]pyridinium tetra-chloridoaurate(III)

In the anion of the title compound, (C(14)H(11)N(4))[AuCl(4)], the Au(III) atom has an almost perfect square-planar coordination. In the crystal structure, an intra-molecular N-H⋯N and intermolecular C-H⋯Cl hydrogen bonds are observed. In addition, there is also a ring-metal inter-action between the pyrazine ring and the Au(III) atom; the distance between the centroid of the pyrazine ring and the Au(III) atom is 3.628 (2) Å.

2,9-Dimethyl-4,7-diphenyl-1,10-phenanthrolin-1-ium tetra-chloridoaurate(III)

Both the cation and anion of the title compound, (C(26)H(21)N(2))[AuCl(4)], are disposed about a plane of mirror symmetry. The 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinium ring is oriented at a dihedral angle of 44.2 (1)° with respect to the planar phenyl ring systems. The Au(III) atom has a square-planar environment defined by four Cl atoms. The crystal structure is stabilized by C-H⋯π and Au⋯π ring-metal (3.551 Å) inter-actions. In the crystal structure, the mol-ecules stack along the c axis via N-H⋯N hydrogen-bond inter-actions.

NMR and theoretical study of the cooperative interaction of hydrated proton with dibenzo-24-crown-8

Interaction of hydrated protons (HPs) with dibenzo-24-crown-8 (DBC in nitrobenzene-d(5) was studied by (1)H and (13)C NMR under assistance of ab initio-density functional theory (DFT) quantum calculations. HPs were afforded by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) with 3.5 M excess of H(2)O. The forming of a complex between HP and DBC leads to marked and additive relative shifts of both (1)H and (13)C signals. This was utilized for the estimation of the stabilization constant K of the complex. Its value is at least 10(6) l/mol, which agrees with the result of independent extraction method (log K = 6.3). Using absolute integral intensities of the HP signal in a water-saturated system, it was shown that the form of HP present in the complex must be H(5)O(2)(+), in accord with formerly published structure of the complex in crystalline form. The investigation of the dynamics of exchange between bound and free DBC by transverse relaxation using variably spaced pulses in the Carr-Purcell-Meiboom-Gill (CPMG) sequence or on-resonance rotating-frame relaxation with variable spin-lock field intensity was partly hampered by the fast relaxation of some signals in the complex because of relative immobilization of its internal motions. In order to remove these effects, a pulse sequence dipolar interaction-free transverse relaxation (DIFTRE) for static DIFTRE was devised and the MLEV17 pulse sequence with high intensity of electromagnetic field was used in a separate series of experiments. Using the results of these latter experiments, the correlation time of exchange was established to be about 0.8 ms, which complied with the shape of the spectra. The accompanying ab initio DFT calculations showed that the apparent symmetry of the molecules of both DBC and its complex with H(5)O(2)(+) was probably the result of averaging of energetically close conformations (five for DBC and four for the complex). Both NMR and the calculations show that the basic mode of binding of the ion in the complex is analogous to that found in crystal but the most pronounced conformation is slightly different.

The nature of the hydrated proton H(aq)+ in organic solvents

The nature of H(H2O)n(+) cations for n = 3-8 with weakly basic carborane counterions has been studied by IR spectroscopy in benzene and dichloroethane solution. Contrary to general expectation, neither Eigen-type H3O x 3 H2O(+) nor Zundel-type H5O2(+) x 4 H2O ions are present. Rather, the core species is the H7O3(+) ion.

1,4,10,13-Tetra-oxa-7,16-diazo-niacyclo-octadecane bis-[tetra-chloridoaurate(III)] dihydrate

The asymmetric unit of the title compound, (C(12)H(28)N(2)O(4))[AuCl(4)](2)·2H(2)O, contains one half-cation, one anion and one water mol-ecule; the cation is centrosymmetric. The Au ion has a square-planar coordination. In the crystal structure, intra-molecular N-H⋯O and O-H⋯O, and inter-molecular N-H⋯O, O-H⋯Cl and N-H⋯Cl hydrogen bonds link the ions and water mol-ecules, forming a supra-molecular structure.

Water trapped in dibenzo-18-crown-6: theoretical and spectroscopic (IR, Raman) studies

Experimental (IR and Raman) and theoretical (Kohn-Sham calculations) methods are used in a combined analysis aimed at refining the available structural data concerning the molecular guests in channels formed by stacked dibenzo-18-crown-6 (DB18C6) crown ether. The calculations are performed for a simplified model comprising isolated DB18C6 unit and its complexes with either H2O or H3O+ guests, which are the simplest model ingredients of a one-dimensional diluted acid chain, to get structural and energetic data concerning the formation of the complex and to assign the characteristic spectroscopic bands. The oxygen centers in the previously reported crystallographic structure are assigned to either H2O or protonated species.

Aqueous Suspension Polymerization of Isobutene Initiated by 1,2-C6F4[B(C6F5)2]2

Lewis acidic, chelating diborane 1 forms stable oxonium acids 2 in the presence of excess MeOH or water. Diborane 1 is shown to be an effective co-initiator for the suspension polymerization of isobutene in aqueous media at sufficiently low temperatures. Poly(isobutene) or butyl rubber is obtained at moderate to high conversion and with Mw < 200 K and PDI approximately 2 under these conditions.

Crystal synthesis of hybrid organometallic–inorganic hydrogen bonded salts of acid oxoanions

Partially deprotonated inorganic oxoanions derived from sulfuric and phosphoric acids have been used to assemble organometallic cations in inorganic-organometallic hybrid systems. The organometallic sandwich cations [(eta(5)-C(5)H(5))(2)Co]+, [(eta(5)-C(5)Me(5))(2)Co]+ and [(eta(5)-C(5)Me(5))(2)Fe]+ have been used because they do not interfere with hydrogen bonding formation forcing self-assembling of the inorganic acids anions HSO(4)(-) and H(2)PO(4)(-) into hydrogen bonded mono- and bi-dimensional networks.

Slow anion exchange, conformational equilibria, and fluorescent sensing in venus flytrap aminopyridinium-based anion hosts

The synthesis, anion binding, and conformational properties of a series of 3-aminopyridinium-based, tripodal, tricationic hosts for anions are described. Slow anion and conformational exchange on the (1)H NMR time scale at low temperature, coupled with NMR titration, results in a high level of understanding of the anion-binding properties of the compounds, particularly with respect to significant conformational change resulting from induced fit complexation. Peak selectivity for halides, particularly Cl(-), is observed. The approach has been extended to dipodal and tripodal podands based on 3-aminopyridinium "arms" containing photoactive anthracenyl moieties. The 1,3,5-tripodal host shows a remarkable selectivity for acetate over other anions, in contrast to the analogous unsubstituted tris(3-aminopyridinium) analogue, despite the fact that low-temperature (1)H NMR experiments reveal a total of four acetate-binding conformations. Photodimerization of anthracene units results in the formation of potential fluorescent anion sensors.