Ya. S. Vygodskii

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.

Zwitterionic titanoxanes {Cp[η5-C5H4B(C6F5)3]Ti}2O and {(η5-iPrC5H4)[η5-1,3-iPrC5H3B(C6F5)3]Ti}2O as catalysts for cationic ring-opening polymerization

Abstract Zwitterionic titanoxanes {Cp[η5-C5H4B(C6F5)3]Ti}2O (I) and {(η5- i Pr C5H4)[η5-1,3- i Pr C5H3B(C6F5)3]Ti}2O (II), which contain two positively charged Ti(IV) centres in the molecule, are able to catalyse the ring-opening polymerization of e-caprolactone (e-CL) in toluene solution and in bulk. The process proceeds with a noticeable rate even at room temperature and accelerates strongly on raising the temperature to 60xa0°C. The best results have been obtained on carrying out the reaction in bulk. Under these conditions, the use of I as a catalyst (e-CL:I = 1000:1) gives at 60xa0°C close to quantitative yield of poly-e-CL with the molecular mass of 197xa0000. An increase in the e-CL:I ratio to 6000:1 increases the molecular mass of poly-e-CL to 530xa0000. Tetrahydrofuran (THF) is also polymerized under the action of I albeit with a lesser rate. However, the molecular mass of the resulting poly-THF can reach rather big values under optimal conditions (up to 217xa0000 at 20xa0°C and the THF:I ratio of 770:1). A rise in the reaction temperature from 20 to 60xa0°C results here to a decrease in the efficiency of the process. Titanoxane II is close to I in its catalytic activity in the e-CL polymerization but it is much less active in the polymerization of THF. Propylene oxide (PO), in contrast to e-CL and THF, gives with I only liquid oligomers in wide temperature and PO:I molar ratio ranges (−30 to +20xa0°C, PO:I = 500–2000:1). γ-Butyrolactone and 1-methyl-2-pyrrolidone are not polymerized under the action of I at room temperature. The reactions found are the first examples of catalysis of the cationic ring-opening polymerization by zwitterionic metallocenes of the group IVB metals.

Reactions of imides with samarium(ii) iodide

The tendency of a series of imides and lactams to react with samarium(II) iodide was investigated. Under the action of Sml2 at ∼20 °C, one of the carbonyl groups ofN-phenylphthalimide was reduced to a CHOH or CH2 group depending on the molar ratio of the reagents and the order of their introduction into the reaction mixture. Both CO groups ofN-acetylcaprolactam are reduced with SmI2 under similar conditions, whereas the CO group of ε-caprolactam is not reduced by SmI2.

The reductive cocondensation of chlorotrimethylsilane and dichlorodimethylsilane

Linear and cyclic permethyloligosilanes were prepared by the Wurtz-type cocondensation of chlorotrimethylsilane and dichlorodimethylsilane in the presence of sodium metal or samarium iodide as reducing agents. The yields and composition of the reaction products depend on the cocondensation conditions.

Spectroscopic and electrochemical properties of mixed-valence RhI-RhIII complexes with a cyanide bridge

Electronic spectra and redox potentials of new mixed-valence RhI-RhIII complexes linked by a cyanide bridge were measured and studied. For these compounds, interaction between rhodium atoms in the molecule is low (a case of “fixed valences”), and no intervalence transition from RhI to RhIII was observed in the 7000 to 50000 cm−1 range. Some of the complexes in the solid state have additional absorption bands in the diffuse reflectance spectra related to the interaction of orbitals (with appropriate symmetry) of Rh(i) fragments of adjacent complex molecules.

Synthesis and investigation of mono- and binuclear cyano-bridged complexes of rhodium, ruthenium, and palladium

Binuclear RhIII and RuII complexes of the [M1-CN-M2]+BF4− (M1 and/or M2 are (η5-Cp)(η3-C3H5)Rh and (η6-C6H6)(η3-C3H5)Ru) type, heteronuclear organometallic compound (η5-Cp)(η3-C3H5)RhCNPd(η3-C3H5)Cl, and mononuclear RhIII and RuII complexes [(η3-C3H5)LM(MeCN)]+BF4− (M = Rh, L = η5-Cp; M = Ru, L = η6-C6H6) were synthesized. An electrochemical study of these compounds in solutions demonstrates that the bond between the bridged CN ligand and the metal atoms is rather strong, and there is no dissociation into mononuclear fragments in solutions. The kinetics of the reaction of [(η5-Cp)(η3-C3H5)Rh(MeCN)]+BF4− with halide ions was studied by electrochemical methods. The ligand exchange proceeds by a bimolecular dissociative-exchange mechanism.

THE REDUCTION OF AROMATIC NITRO COMPOUNDS BY OXIRANES

Aromatic nitro compounds are reduced to the corresponding amines by epoxides at elevated temperatures (>170 °C).