The preparation and X-ray structural study of complexes that catalyze isocyanate cyclotrimerization

A 11-complex of trinitrophenol with benzyldimethylamine (1) and a 111-complex, the product of the interaction of benzyldimethylamine, glycidyl phenyl ether, and phenol (2), have been synthesized and characterized by means of X-ray analysis. Complex1 is a precursor for the catalysts of selective isocyanate cyclotrimerization, while complex2 is one of those catalysts. In the crystal structure complex1 forms H-bonded cationic-anionic aggregates with proton transfer from phenol to the N-atom of the tertiary amine. Complex2 crystallizes as a monohydrate (2a) with a strong H-bond between the quaternary ammonium and phenolic components, and exists in crystals in the form of globular H-bonded dimeric hydrates. Possible pathways of dissociation of complex2a are discussed. The data obtained may be used as a basis for further interpretation of the regularities of cyclotrimerization of isocyanates catalyzed by complexes of this type.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No 1, pp. 92–97, January, 1993.     

Viscometry in the study of molecular complexes

Viscometric method has been used to study the interaction between the weak interacting systems such as benzene-CCl₄-cyclohexane, toluene-CCl₄-cyclohexane ando- xylene-CCl₄-cyclohexane. The equilibrium constants and other thermodynamic parameters have been reported and compared with literature data.     

Ab initio study of the complexes of halogen-containing molecules RX (X=Cl, Br, and I) and NH3: towards understanding the nature of halogen bonding and the electron-accepting propensities of covalently bonded halogen atoms

Ab initio calculations have been performed on a series of complexes formed between halogen-containing molecules and ammonia to gain a deeper insight into the nature of halogen bonding. It appears that the dihalogen molecules form the strongest halogen-bonded complexes with ammonia, followed by HOX; the charge-transfer-type contribution has been demonstrated to dominate the halogen bonding in these complexes. For the complexes involving carbon-bound halogen molecules, our calculations clearly indicate that electrostatic interactions are mainly responsible for their binding energies. Whereas the halogen-bond strength is significantly enhanced by progressive fluorine substitution, the substitution of a hydrogen atom by a methyl group in the CH(3)X...NH(3) complex weakened the halogen bonding. Moreover, remote substituent effects have also been noted in the complexes of halobenzenes with different para substituents. The influence of the hybridization state of the carbon atom bonded to the halogen atom has also been examined and the results reveal that halogen-bond strengths decrease in the order HC triple bond CX > H(2)C=CHX approximately O=CHX approximately C(6)H(5)X > CH(3)X. In addition, several excellent linear correlations have been established between the interaction energies and both the amount of charge transfer and the electrostatic potentials corresponding to an electron density of 0.002 au along the R-X axis; these correlations provide good models with which to evaluate the electron-accepting abilities of the covalently bonded halogen atoms. Finally, some positively charged halogen-bonded systems have been investigated and the effect of the charge has been discussed.     

New dinuclear palladium complex with a Chinese-lantern structure

The new dinuclear palladium complex Pd₂(-S,N-SC₇H₅N₂)₄ with a Chinese-lantern structure was synthesized by the reaction of K₂PdCl₄ with 2-mercaptobenzimidazole and structurally characterized by X-ray diffraction analysis.     

Structures of deoxypeganine salts

The structures of deoxypeganine (DOP) hydrochloride and oxalate were solved by x-ray structure analysis. An infinite chain along the crystallographic c axis was formed in the crystal structure of DOP oxalate. A molecular framework consisting of Cl anions and DOP cation protonated at N1 was found in the structure of unhydrated DOP hydrochloride. The molecular packing of the “host” (DOP cation) was pseudoisostructural in the studied ion-molecular crystals but differed from other known DOP salts. The “guest” molecules (acid anions) in the studied and known DOP salts formed different intermolecular contacts. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 280–283, May–June, 2006.     

Nontrivial structural organization of pivalate complexes with the fragment {Fe2Li(μ3-O)}

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Feasibility of using solid sampling graphite furnace atomic absorption spectrometry for speciation analysis of volatile and non-volatile compounds of nickel and vanadium in crude oil

A method for the direct determination of volatile and non-volatile nickel and vanadium compounds in crude oil without previous treatment using direct solid sampling graphite furnace atomic absorption spectrometry is proposed. The crude oil samples were weighed directly onto solid sampling platforms using a microbalance and introduced into a transversely heated solid sampling graphite tube. In previous work of our group losses of volatile nickel and vanadium compounds have been detected, whereas other nickel and vanadium compounds were thermally stable up to 1300 and 1600 °C, respectively. In order to avoid this problem different chemical modifiers (conventional and permanent) have been investigated. With 400 μg of iridium as permanent modifier, the signal started to drop already after two atomization cycles, possibly because of an interaction of nickel (which is a catalyst poison) with iridium. Twenty micrograms of palladium applied in each determination was found to be optimum for both elements. The palladium was deposited on the platform and submitted to a drying step at 150 °C for 75 s. After that the sample was added onto the platform and submitted to the furnace program. The influence of sample mass on the linearity of the response and on potential measurement errors was also investigated using four samples with different nickel content. For the sample with the lowest nickel concentration the relationship between mass and integrated absorbance was found to be non-linear when a high sample mass was introduced. It was suspected that the modifier had not covered the entire platform surface, which resulted in analyte losses. This problem could be avoided by using 40 μL of 0.5 g L⁻¹ Pd with 0.05% Triton X-100. Calibration curves were established with and without modifier, with aqueous standards, oil-in-water emulsions and the certified reference material NIST SRM 1634c (trace metals in residual fuel oil). The sensitivity for aqueous standards and emulsions was close to that for SRM 1634c, making possible the use of aqueous standards for calibration. The limits of detection and quantification obtained for nickel and vanadium under this condition were found to be 0.02 and 0.06 μg g⁻¹, respectively, for both elements, based on 10 mg of sample. Nickel and vanadium were determined in the samples with (total Ni and V) and without the use of Pd (thermally stable compounds), and the concentration of volatile compounds was calculated by difference. The results were compared with those obtained by high-resolution continuum source graphite furnace atomic absorption spectrometry by emulsion technique; no significant differences were found for total Ni and V at the 95% confidence level according to a Student's t-test.     

Adsorption Equilibrium and Kinetics of Egg-White Proteins on Immobilized Metal Ion Affinity Gels for Designing Fractionation

Designing an Immobilized Metal ion Affinity (IMA) chromatographic process on large scale demands a thorough understanding to be developed regarding the adsorption behaviour of proteins on metal loaded IMA (IMA-M(II)) gels and the characteristic adsorption parameters to be evaluated. This research investigation illustrates the significance of these aspects for the proposed fractionation of chicken egg-white proteins on these gels. Consequently, a systematic investigation of the adsorption characteristics of three chicken egg-white proteins viz., ovalbumin, conalbumin and lysozyme on Cu(II) and Ni(II) loaded IMA gels, iminodiacetate (IDA) and tris(2-aminoethyl)amine (TREN), has been undertaken. These gels differ in their selectivity towards the proteins of interest under the identical sets of experimental conditions. While TREN-Ni(II) was selective only for lysozyme, IDA-Cu(II), IDA-Ni(II) and TREN-Cu(II) showed varying affinities for all the three proteins. The equilibrium and kinetic data were analysed using various theoretical models and adsorption parameters were quantified. On the basis of these investigations, various strategies have been proposed for the efficient large-scale fractionation of chicken egg-white proteins on these gels.