Titanocen-cyandithioformiat-Komplexe

The reaction of titanocene dichloride,Cp ₂TiCl₂ (Cp=⁵-C₅H₅), with one or two equivalents of sodium cyanodithioformate affords the new mono- or bis(dithiocarboxylato) derivativesCp ₂TiCl(S₂CCN) (1) andCp ₂Ti(S₂CCN)₂ (2). Elimination of sulfur converts2 into the metallacyclicCp ₂TiS₂C₂(CN)₂ (3), which does not react with the diene isoprene, but can be reconverted into the appropriate titanocene dihalides by chlorine or bromine.

     

Synthesis and study of η5-C5H5-3,1,2-MIIIC2B9H11−n F n (M = Co,Fe;n = 1−4)

B-Flourosubstituted cyclopentadienyldicarbollylcobalt and -iron were synthesized. Electrochemical studies of iron ⁵-C₅H₅-3,1,2-FeC₂B₉H_11–n F _n (n = 2–4) complexes were carried out.¹⁹F NMR, UV, and IR spectra of the cobalt and iron complexes were obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2984–2989, December, 1996,     

Crystal and Molecular Structure of Cu(II) Bis-(2-methoxy-2,6-dimethyl-3-imino-5-heptanonate)

A new compound from the series of alkoxyketoiminates, Cu(II) bis-(2-methoxy-2,6-dimethyl-3-imino-5-heptanonate), has been synthesized and studied by X-ray crystallography. Crystal data for CuO₄N₂C₂₀H₃₆: a=10.154(1), b=9.921(1), c=11.684(2) , =96.17(1)°, space group P2₁/c, Z=2, dcalc =1.226 g/cm³, R=0.037. The structure is molecular and built from isolated trans-complexes. The copper atom has a plane square environment of two oxygen atoms (Cu–O 1.93 ) and two nitrogen atoms (Cu–N 1.90 ). The O–Cu–N chelate angle is 91.7°. The complex has an intramolecular hydrogen bond, N–H...O 2.16 , involving the alkoxy oxygen atom. The molecular packing in the crystal is close to that of copper(II) dipivaloylmethanate. The calculated van der Waals intermolecular interaction energies and thermogravimetric characteristics of the complexes are compared.     

Photochemical addition of diethyl ether to β,β,β',β'-tetrakis(trifluoromethyl)divinyl ether

The 1:1 adducts of diethyl and ,,','-tetrakis(trifluoromethyl)divinyl ether (1),i.e., 3,5-(ee)-bis[2,2,2-trifluoro-1-(trifluoromethyl)ethyl]-2,6-dimethyl-1,4-dioxane (2) (3 isomers) and 4-ethoxy-1,1,1-trifluoro-2-trifluoromethyl-3-[3,3,3-trifluoro-2(trifluoromethyl)propenyloxy]pentane (3), have been obtained by UV-irradiation of a solution of divinyl ether1 in diethyl ether. The X-ray structural investigation of the all-(e)-isomer of dioxane (2) has been carried out.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 85–88, January, 1994.     

Charge-transfer complexes betweenp-toluidine and iodine in solution: A kinetic study

The kinetics of charge-transfer interaction betweenp-toluidine and iodine in methylene chloride was investigated in depth. Thethermal process of formation of theinner complex was found to proceed to an equilibrium. Thephotochemical process follows a different reaction coordinate, going through the formation of an exciplex between the excitedouter complex and the amine ground state. In both cases the same ionic complex (Am ₂I⁺I ₃ ^– , whereAm stands forp-toluidine) was detected as the final product.

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Kinetische Untersuchung der Charge-Transfer-Komplexe zwischenp-Toluidin und Jod

Zusammenfassung Die Kinetik der Charge-Transfer-Wechselwirkung zwischenp-Toluidin und Jod in Methylenchlorid wurde ausführlich untersucht. Derthermische Prozeß, der zur Bildung desinner-Komplexes führt, geht bis zu einem Gleichgewicht. Derphotochemische Prozeß folgt einer unterschiedlichen Reaktionskoordinate und verläuft über die Bildung eines Exziplexes zwischen dem angeregtenouter-Komplex und dem Amin im Grundzustand. In beiden Fällen wurde derselbe ionische Komplex (Am ₂I⁺I ₃ ^– , wobeiAm fürp-Toluidin steht) als Endprodukt festgestellt.

     

Synthesis and reactions of dicarbonyl (η2-indene)-η5-indenyl complexes of manganese and rhenium

Photochemical reactions of M(CO)₃(⁵-C₉H₇), where M=Mn (1) or Re (2), with indene have produced ²-indene complexes M(CO)₂(²-C₉H₈)(⁵-C₉H₇), where M=Mn (3) or Re (4). Deprotonation of complex3 witht-BuOK in THF at –60 °C gives the anion [Mn(CO)₂(¹-C₉H₇)(⁵-C₉H₇)^– (5), in which there occurs a rapid interchange of the Mn(CO)₂(⁵-C₉H₇) group between positions 1 and 3 in the ¹-indenyl ligand. The reaction of complex4 with Ph₃CPF₆ in CH₂Cl₂ at 0 °C leads to the complex [Re(CO)₂(³-C₉H₇)(⁵-C₉H₇)PF₆, whereas the similar reaction of complex3 gives only decomposition products even at –20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1280–1285, July, 1993.     

Molecular and electronic structure of some bowl-shaped unsaturated hydrocarbon molecular systems,possible precursors of C60 fullerene

The AMI calculations of hydrocarbon molecules C₂₀H₁₀ (1) and C₃₀H₁₀ (2) and anions C₂₀H₁₅ ^–4 (3) and C₃₀H₁₅ ^– (4) have been performed with the full energy optimization of the geometric parameters. The chosen topology of the carbon framework of the studied compounds is identical to the topology of the corresponding carbon fragments of C₆₀ fullerene. Analysis of the structure of the frontier orbitals of systems1–4 demonstrated that the tendency of the C₂₀H₁₀ molecule to form sandwich -complexes of the ⁵-type with transition metal atoms is small; however, this tendency is significantly larger than that of C₃₀H₁₀. Moreover, the exclusion of the five-membered cycle of bowlshaped unsaturated hydrocarbon molecules and anions from the conjugated system (as a result of the conversion of five framing C atoms to saturated carbon centers) favors the stabilization of their ⁵-type -complexes with M(C₅H₅) species. The stability of these complexes must approach the stability of classical sandwich complexes of the ferrocene type. The results obtained have been extrapolated to polyhedral C₆₀ and C₇₀ carbon clusters.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 855–858, May, 1995.This work was financially supported by the Russian Foundation for Basic Research (Projects No. 93-03-4101 and 93-03-18725).     

Formation of closo-rhodacarboranes containing η2,η3-(CH2=CHC5H6) ligand in the reaction of μ-dichloro-bis[(η4-norbornadiene)rhodium] with nido-dicarbaundecaborates [K][nido-7-R1-8-R2-7,8-C2B9H10]

The reactions of a complex [(⁴-C₇H₈)RhCl]₂ (C₇H₈ is norbornadiene) with salts of substituted nido-dicarbaundecaborates, [K][nido-7-R¹-8-R²-7,8-C₂B₉H₁₀] (R¹ = R² = H (a); R¹ = R² = Me (b); R¹, R² = 1,2-(CH₂)₂C₆H₄ (c); R¹ = Me, R² = Ph (d)), in CH₂Cl₂ afforded new closo-(²,³-(4-vinylcyclopenten-3-yl))rhodacarboranes. The structures of the compounds were studied by multinuclear NMR spectroscopy. A probable mechanism of the rearrangement of the norbornadiene ligand is discussed.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1875–1878, September, 2004.     

Transformationen von β-Glycofuranosylisocyaniden in Tetrahydrofuranderivate

Summary Readily available -glycofuranosyl isocyanides1,2,4,5,6,18,19,20 are transformed into the corresponding protected tetrahydrofurans21,22,23,24,25,26 by means of tributyltin hydride andAIBN. The synthesis of18 and19 by dehydration of the formamide15 is described. Starting with 6-deoxy-1,2-O-isopropyliden--D-allofuranose (7) crystalline 1,2-O-diacetyl-3,5-dibenzoyl--D-allofuranose (9) is obtained.9 is first transformed into the anomeric azides11,12 and13,14 and subsequently into the formamide15.

     

Studies of the energy spectrum of α, ω- substituted polymethine chains. II. Polymethine chains with odd number of methine groups

The analysis of the experimental data for the energy of the longest wavelength optical transitions _n,opt of substituted polymethines X (CH)_2n+1 X shows that in the asymptotic case (n) _,opt does not tend to zero, as it follows from the empirically established correlations, but has a finite, non-zero value. It is shown that the energy gap of odd polymethines is the same as that of the even polymethines - the polyenes (E 2 eV). The substituents (X N, O, B) are responsible for the appearance of levels in the gap. These, depending on the substituent character, are vacant (X B) or occupied (X N, O). The transition from or to such a level determines the longest wavelength optical transition energy of polymethines.     

Band structure of even and ions of odd polyenes

The analysis of experimental data for singlet transitions (E _n) of even polyenes (I), cations (II) and anions (III) of odd polyenes show that for infinite chains E (I)/E (II)=E (I)/E (III) = 2:1. It is shown that the energy gap is equal for the three systems. In cases (II) and (III) there is a level (NBMO) in the gap which is vacant in (II) and occupied in (III). That is why the first optical transition in (II) and (III) depends on the semiwidth of the gap.     

Interaction of dicyclopentadienyl chloride complexes of yttrium and lutetium with sodium naphthalenide

The reaction of Cp₂LuCl with sodium naphthalenide gives an anionic hydride complex [(Cp₂LuH)₃H][Na(THF)₆] (1) and complex Cp₂Lu(2-C₁₀H₇)(THF) (2) containing a -bonded naphthyl ligand. The structure of1 was confirmed by X-ray analysis. When Cp₂YCl is used as the starting material, Cp₃Y and an anionic hydride complex also containing a -naphthyl ligand are formed. A reaction mechanism involving the formation of an unstable complex [(Cp₂Ln⁺)₂(C₁₀H² ₈-)] (4) and its fragmentation into hydride and -naphthyl species is proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 20–20, November, 1994.     

Effects of the donor properties of alkylamines on the structural and charge characteristics of (η3-allyl)· Palladium complexes

Density functional (DFT) calculations have been performed on (³-allyl)palladium complexes with amines. The effects of the donor properties of amines on the structure of the complexes and electron density distribution have been analyzed. As the number of donor methyl groups increases in the series NH_3–n (CH₃) _n , where n = 0, 1, 2, the Pd-C bond, which is in the trans position relative to the amine, becomes longer, leading to increased probability of an intraspheric attack of the amine on the appropriate terminal carbon atom of the allyl ligand; when n = 3, this tendency is violated.Original Russian Text Copyright © 2004 by O. Yu.Tkachenko and A. P. BelovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 442–444, May–June, 2004.     

Some peculiarities of hydrosilylation of α,ω-divinyloligosilanes

The stability of Si-Si bonds in linear and cyclic permethyloligosilanes and in ,-divinyloligosilanes under conditions of hydrosilylation in the presence of the Speier's catalyst was studied. Polycarbosilanes containing silylene fragments in their backbone chains were prepared by the reaction of 1,4-bis(dimethylsilyl)benzene with ,-divinyloligosilanes. It was found that the structure of these polymers is disturbed due to the side reaction involving the cleavage of the Si-Si bond in vinyloligosilanes under the action of H₂PtCl₆.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2547–2549, October, 1996.     

Triterpene glycosides ofScheffleropsis angkae. I. Structure of glycosides L-B1, L-B2, L-H1, and L-H2

The structures of four triterpene glycosides from the leaves ofScheffleropsis angkae (Araliaceae) are found by chemical methods and NMR spectroscopy to be the 3-O--L-arabinopyranosides of oleanic and ursolic acids and their 28-O--L-rhamnopyranosyl-(14)-O--gentiobiosyl esters, which are designated L-B₁, L-B₂, L-H₁, and L-H₂, respectively. The glycoside L-H₂ is new.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 136–138, March–April, 2000.     

Zur Reaktion von Permethylcyclosilanen mit Halogenen

The series of ,-diiodopermethylpolysilanes, I(SiMe ₂) _n I, (n=4–6) andX(SiMe ₂)₄ X, (X=Cl, Br) has been prepared by the action of halogen on the corresponding cyclic compounds (SiMe ₂) _n . The mass spectra, NMR-, IR- andRaman-spectra of these compounds have been recorded.

Herrn Prof. Dr.Josef Schurz zum 60. Geburtstag gewidmet.     

Synthesis of Co3(CO)7(μ-η3-Allyl)(μ3-X) Complexes (X=S, Se) and Structure of the Selenium Derivative

The complexes Co₃(CO)₉( ₃-X) (X=S, Se) can be reduced to the corresponding anionic species [Co₃(CO)₉( ₃-X)]^–, which react with allyl bromide to give Co₃(CO)₇(- ³-C₃H₅)( ₃-X) (X=S, Se). These are the first two cobalt complexes containing the bridging - ³-allyl ligand. The structure of the selenium complex was determined by X-ray crystallography. Crystal data for Co₃(CO)₇(- ³-C₃H₅)( ₃-Se) are as follows: space group P2₁/c, a=9.051(2) Å, b=8.102(2) Å, c=21.27(4) Å, =93.82(3)°, Z=4, and R=0.0565 for 2491 observed reflections.     

Crystal Structure of Ammonium(2.2.2‐cryptand) Thiocyanate Monohydrate

Crystals of the ammonium (2.2.2cryptand) thiocyanate monohydrate complex, [NH₄(2.2.2Crypt)]⁺ × SCN^- · H₂O, were studied by Xray structural analysis: space group P2/c, a = 11.303(2)*angst;, b = 8.313(1), c = 14.392(3), = 110.39(2)°, Z = 2, 3680 independent measured reflections, R = 0.064. This complex is of the guest–host type: the cryptand ligand cavity contains the NH₄ ⁺ cation with statistically disordered H atoms forming H bonds with each of its O and N heteroatoms. The SCN^- anions and H₂O molecules are linked by H bonds to form chains that are infinite along the z axis.     

Novel Synthesis of 2β,3β,20β-Triacetoxy-5 -pregnan-6-one

Pregnenolone (2) is used in a novel synthesis of 2,3,20-triacetoxy-6-ketosteroid (6), a key intermediate in the preparation of 20-hydroxyecdysone (1)     

Dissociation of diimide

Parts of the potential energy surface of N₂H₂ have been studied using CASSCF- and contracted CI-methods. Of particular interest was the concerted dissociation of cis- and trans-diimide into N₂ and H₂, since the trans-dissociation is symmetry allowed and the cis-dissociation forbidden. Three different saddle points were located, of which only one, of C ₂- symmetry, is a true transition state. Elaborate numerical gradient methods using exact Hessians and update procedures had to be used to find these saddle points on the unexpectedly complex N₂H₂-surface. The barrier height with respect to trans-diimide is 61 kcal/mol after vibration correction. Since this energy is higher than the barrier for interconversion, cis- and trans-diimide have the same transition state. It is further found that diimide preferably dissociates stepwise, by losing one hydrogen at a time, rather than in a concerted way. This conclusion is drawn basically because the geometry of the transition state for the concerted dissociation has a very long H-H distance of 5.6 a.u. The N-H bond energy in trans-diimide is 56 kcal/mol after vibration correction.