K. A. Lyssenko

IR and X-ray Study of Polymorphism in 1-Alkyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imides

The crystal structure of [C(n)mim]NTf(2) (n = 2, 4, 6) was studied for the first time simultaneously by X-ray diffraction method and IR spectroscopy. The temperature-dependent IR spectrum for crystalline [C(4)mim]NTf(2) was demonstrated to correlate with both the X-ray data and the calorimetric results obtained earlier. Therefore, it was found that IR spectroscopy is able to establish the correspondence between the X-ray and the calorimetric data in this case. The joint use of X-ray diffraction, IR spectroscopy, and quantum-chemical calculations allowed us to determine the structure of all [C(2)mim]NTf(2) crystalline modifications obtained earlier by adiabatic calorimetry measurements. Thus, a new approach for the future identification of ionic liquid crystal structure by use of temperature-dependent infrared spectroscopy is suggested and justified.

Carboranes: chemical concepts derived from the AIM study of the experimental and theoretical electron density distribution functions

On the basis of high-resolution X-ray diffraction studies as well as quantum-chemical calculations of five carborane derivatives the peculiarities of electron density distribution functions have been analyzed. The data obtained permitted a deeper insight into the nature of unusual properties of the C-C bond in o-carborane and investigating intermolecular H ... H interactions in crystal. It was shown that such an approach allows estimating the values of lattice energy for the crystals of carboranes.

Antiferromagnetic complexes with metal–metal bonds. ☆: Part XXX. Synthesis and molecular structures of the antiferromagnetic adducts [Cp′Cr(μ-SPh)]2(μ3-Se).ML (Cp′=η5-CH3C5H4, ML=Fe3(μ3-S)2(CO)8, Mn2(CO)9, Mn2(CO)8), paramagnetic complexes Cp′Cr(μ-SPh)3Mn(CO)3 and [Cp′Cr(μ-SPh)]2Te, diamagnetic cluster Cp′2Cr2(μ-SPh)(μ3-S)(μ3-Te)Co(CO)2

The photochemical reactions of antiferromagnetic heterochalcogenic complex [Cp′Cr(μ-SPh)] 2 (μ-Se) ( 1 ) (Cp′=η 5 -CH 3 C 5 H 4 ) with Fe 3 (μ 3 -Se) 2 (CO) 9 or Mn 2 (CO) 10 at room temperature gives new mixed-metal heterochalcogenic clusters [Cp′Cr(μ-SPh)] 2 (μ 3 -Se)Fe 3 (μ 3 -Se) 2 (CO) 8 ( 2 ), [Cp′Cr(μ-SPh)] 2 (μ 3 -Se)Mn 2 (CO) 9 ( 3 ) and [Cp′Cr(μ-SPh)] 2 (μ 4 -Se)Mn 2 (CO) 8 ( 4 ) which are antiferromagnetic (−2 J =256, 230 and 324 cm −1 , respectively) and characterized by X-ray diffraction analysis ( 2 : Cr–Cr 2.763(1) A; Fe–Fe 2.6184(9) and 2.706(1) A; Cr–Se 2.447, 2.460 A; 3 : Cr–Cr 2.762 A; Mn–Mn 2.920 A; Cr–Se 2.447, 2.460 A; 4 : Cr–Cr 2.816 A, Mn–Mn 2.835 A, Cr–Se 2.464 A). The photochemical reaction of 1 and Mn 2 (CO) 10 at higher temperature gives the paramagnetic complex Cp′Cr(μ-SPh) 3 Mn(CO) 3 ( 5 ) with a weak Cr–Mn bond (3.0239 A). The new heterochalcogenic complex [Cp′Cr(μ-SPh)] 2 (μ-Te) ( 6 ) which obtained at the interaction of [Cp′Cr(CO)(μ-SPh)] 2 with Te and was studied by X-ray method (Cr–Cr 2.772 A, Cr–S 2.359 A, Cr–Te 2.601–2.607 A, Cr–Te–Cr 64.3°), reacted with Co 2 (CO) 8 with formation of the diamagnetic mixed-metal heterochalcogenic cluster [Cp′ 2 Cr 2 (SPh)](μ 3 -S)(μ 3 -Te)Co(CO) 2 ( 7 ) (Cr–Cr 2. 646 A, Cr–Co 2.627 A–2.623 A, Cr–μ 3 -S 2.282–2.299 A, Co–μ 3 -S 2.199 A, Cr–μ 3 -Te 2.630–2.618 A, Co–μ 3 -Te 2.466 A, Cr–μ-S Ph 2.335 A). The role of super-exchange spin–spin interaction through the chalcogen bridge atom is discussed.

Vibrational spectra and structure of cesium salts of icosahedral monocarba-closo-dodecarborate anion, [CB11H12]–, and its nido-derivative, [CB100H13]–

The Raman and IR spectra of the cesium salts of monocarbon carboranes, [closo-CB11H12]– and [nido-CB10H13]–, are reported and the assignment of the normal modes is given. Quantum-chemical calculations of the geometry of undistorted closo-anions B12H122– and CB11H12– were carried out and normal coordinate analysis for the latter was performed. Structural parameters and spectral characteristics of isoelectronic closo-polyhedra [B12H12]2–, [CB11H12]–, and p-C2B10H12 and those of the closo- and nido-structures were compared.

Electron density distribution in vanadocene (η5-C5H5)2V and mixed metallocenes (η5-C5H5)M(η5-C7H7) (M = Ti, V, or Cr) and (η5-C5H5)Ti(η8-C8H8). Effect of the nature of the cyclic ligand on the character of the M--(π-ligand) bond

The electron density distribution and atomic displacements were analyzed based on the results of precision low-temperature X-ray diffraction studies of a series of isostructural (Pnma, Z = 4) mixed metallocenes (η5-C5H5)M(η5-C7H7) (M = Ti, V, or Cr) and (η5-C5H5)Ti(η8-C8H8). The barriers to rotation of the cyclic ligands were evaluated based on rms libration amplitudes. Analysis of the deformation electron density demonstrated that the character of the M--(π-ligand) chemical bond depends substantially both on the nature of the metal atom and the size of the ligand. Lowering of the local symmetry of the (η5-C5H5)M(η5-C7H7) complexes to CS leads to distortion of the cylindrical symmetry of the electron density distribution observed in vanadocene (η5-C5H5)2V and titanocene (η5-C5H5)Ti(η8-C8H8).

Chemical bonding in isolated molecules and crystals of zwitterionic pentacoordinate silicon chelates

The electronic structures of a number of zwitterionic pentacoordinate silicon chelates were investigated using the results of X-ray diffraction studies and quantum-chemical calculatoins by the MPW1PW91/6-311G(d) method. The topological analysis of the electron density distribution function and the study in the framework of the natural bond orbital partitioning scheme showed that the character of chemical bonding in the axial fragments of the molecules under consideration changes from dative to three-center, four-electron as the silicon atom assumes a trigonal-bipyramidal coordination.

X-ray structures of decamethylplatinocene dication in the crystal of [Pt(η5-C5Me5)2]2+(PF6−)2 and decamethyliridocenium cation in the crystal of [Ir(η5-C5Me5)2]+(BPh4−) · CH2Cl2

Abstract The molecular crystal structures of the [Ir( η 5 -C 5 Me 5 ) 2 ] + cation in the complex of [Ir( η 5 -C 5 Me 5 ) 2 ] + (BPh 4 ) − · CH 2 Cl 2 ( 1 ), (space group P l¯, Z = 2), and dication [Pt( η 5 -C 5 Me 5 )] 2+ in the complex of [Pt( η 5 -C 5 Me 5 ) 2 ] 2+ (PF 6 ) 2 − ( 2 ), (space group I 4¯2 d , Z = 8) were proved by an X-ray investigation at 153 K ( R = 0.0661 and 0.0528 for 1 and 2 respectively). X-ray analysis revealed that in both structures the cations and anions are ordered, cation [Ir( η 5 -C 5 Me 5 ) 2 ] + has the staggered conformation, whereas the dication [Pt( η 5 -C 5 Me 5 )] 2+ has the ideal eclipsed one. The distances from the metal to the C 5 Me 5 ring in 1 (1.817(6) A and 1.821 (6) A are close to those in the neutral complex Os( η 5 -C 5 Me 5 ) 2 ( 3 ) (1.810(7) A). The similar distance in the dication [Pt( η 5 -C 5 Me 5 ) 2 ] 2+ in 2 (1.84(1) A) is slightly elongated in comparison with 1 and 3 .

Synthesis of 2-monofunctionalized 2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones

New (1R*,5S*)-2-R-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones containing the terminal carboxy or hydroxy group in the substituent R were synthesized by cyclocondensation of 4,5-dihydroxyimidazolidin-2-one with 1-R-ureas. Single-crystal X-ray diffraction analysis showed that 2-carboxyethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione crystallizes as a racemate.

Hydrogen bond in 3-acetyl-4-hydroxycoumarin: X-ray diffraction study and quantum-chemical calculations

The proton transfer and the character of the strong intramolecular O--H...O hydrogen bond (O...O 2.442 Å) in 3-acetyl-4-hydroxycoumarin were analyzed based on the results of X-ray diffraction study in the temperature range from 100 to 353 K and quantum-chemical B3LYP/6-31G(d,p) calculations. The barrier to proton transfer along the H-bond line is low (2 kcal mol–1). However, no proton transfer was observed in the crystal at 100 K. Baders topological analysis of the electron density distribution both in the crystal and in the isolated molecule demonstrated that the hydrogen bond corresponds to an intermediate type of interatomic interactions (E(r) < 0, ∇2ρ(r) > 0 at the critical point (3, –1)).

Reaction of 1,2-dialkyldiaziridines with ketenes as a new approach to cyclic and linear systems containing the N— C—N fragment

The reaction of 1,2-dialkyldiaziridines with ketenes proceeds through the N—N bond cleavage to form three types of structures containing the N—C—N fragment, viz., 1,3-dialkylimidazolidin-4-ones, 3,5-diacyl-3,5-diazahept-1-enes, and β-lactams. The reaction pathway depends on the reaction conditions and the structures of the starting compounds.