Specifics of titanium tetrafluoride complexation with Ph<Subscript>2</Subscript>P(O)(CH<Subscript>2</Subscript>)<Subscript>2</Subscript>C(O)NMe<Subscript>2</Subscript>: The remarkable stability of the seven-membered chelate heterocycle TiOPCCCO and its conformational isomerism in solution

The composition and structure of the products of the reaction of titanium tetrafluoride with Ph₂P(O)(CH₂)₂C(O)NМе₂ (L), the simplest representative of diphenyl[2-(N,N-dialkylcarbamoyl)ethyl]phosphine oxides, in a СН₂Сl₂ have been studied by ¹⁹F and ³¹P NMR. It has been shown for the first time that functionalized phosphine oxides form stable seven-membered chelate heterocycles on complexes of d° transition metals. On the basis of NMR data, previously unknown conformational isomerism of the seven-membered TiOPCCCO heterocycle in solution has been proposed. A simple and rather efficient method of synthesis of the ligand (L) from commercially available reagents has been developed.     

Complexation of TiF<Subscript>4</Subscript> with PhP(O)[CH<Subscript>2</Subscript>C(O)NMe<Subscript>2</Subscript>]<Subscript>2</Subscript> in CH<Subscript>2</Subscript>Cl<Subscript>2</Subscript>: Appearance of a Chiral Center at Chelate Coordination

The reaction of TiF₄ with PhP(O)[CH₂C(O)NMe₂]₂ in CH₂Cl₂ has been studied by ¹⁹F NMR spectroscopy. It has been found that the major reaction products are chelate tetrafluoro complex (η²-L)TiF₄ where the ligand is coordinated to the titanium ion through the P=O and C=O groups and cis-TiF₄(ОР···L)₂ where both ligands are coordinated to the central ion through the more basic P=O groups. Spectral features of the tetrafluoro chelate have been studied, which have been attributed for the first time to the appearance of a chiral center at chelate coordination. The character of manifestation of conformational isomerism of the chelate ring and chiral center in the chelating ligand in mixed octahedral complexes of d⁰ transition metal fluorides in ¹⁹F NMR spectra is discussed.     

Stereoisomerism of Octahedral Titanium <Emphasis Type="Italic">cis</Emphasis>-Tetrafluoro Complexes with Ph<Subscript>2</Subscript>P(O)CH<Subscript>2</Subscript>CH(OH)Me Enantiomers According to <Superscript>19</Superscript>F NMR Data

Effect of enantiomers of a monodentate ligand on the stereoisomerism of mixed octahedral cis-tetrafluoro complexes of d⁰ transition metals has been studied by ¹⁹F{¹H} and ³¹P{¹H} NMR by the example of TiF₄ complexation in CH₂Cl₂ with Ph₂P(O)CH₂CH(OH)Me (L) containing asymmetric carbon atom in the aliphatic hydrocarbon group that constitutes a racemic mixture of enantiomers. Composition of complexes formed in solution has been determined, conclusion has been drawn on the relative stereochemical configuration of the chiral and meso stereoisomers of octahedral complex cis-TiF₄L₂ on the basis of analysis of ¹⁹F NMR spectra, using the heterotropism concept.     

Anharmonic Effect in CH<Subscript>3</Subscript>CH<Subscript>2</Subscript>C(=O)OCH<Subscript>2</Subscript>CH<Subscript>3</Subscript> Decomposition

In this paper, using the B3LYP functional and CCSD(T) method with 6-311++G** basis set, the harmonic and anharmonic rate constants in the unimolecular dissociation of ethyl propanoate have been calculated using Rice–Ramsperger–Kassel–Marcus theory. The anharmonic rate constants of the title reaction have also been examined, the comparison shows that, the anharmonic effect especially in the case of high total energies and temperature for channels 3 to 6 is significant, so that the anharmonic effect cannot be neglected for unimolecular dissociation reaction of CH₃CH₂C(=O)OCH₂CH₃ both in microcanonical and canonical systems.     

Theoretical study on the reaction mechanism of the OH-initiated oxidation of CH<Subscript>2</Subscript>=C(CH<Subscript>3</Subscript>)CH<Subscript>2</Subscript>CH<Subscript>2</Subscript>OH

In the present work, the detailed reaction mechanism and possible products of the OH-initiated oxidation of CH₂=C(CH₃)CH₂CH₂OH (MBO331) have been revealed theoretically for the first time. The potential energy surfaces of various reaction channels both in the absence and presence of O₂ and NO are evaluated at the CCSD(T)/6−31++G(d,p)//MP2(full)/6−311G(d,p)+ZPE*0.95 level. The major products of HCHO + CH₃C(O)CH₂CH₂OH predicted for the title reaction in the presence of O₂ and NO are in agreement with those of similar reactions of unsaturated alcohols with OH radical.     

Effect of structural features of molecules (Cl<Subscript>3</Subscript>PNZ)<Subscript>2</Subscript> (Z = CH<Subscript>3</Subscript> and CH<Subscript>2</Subscript>CH<Subscript>2</Subscript>Cl) on the position exchange of chlorine atoms in the P-Cl fragments

Based on the analysis of structural parameters of molecules (Cl₃PNCH₃)₂ (I) and (Cl₃PNCH₂CH₂Cl)₂ (II) by the quantum-chemical nonempirical calculations the following was revealed. The structure of I and II dimers has geometric features, which have a decisive influence on the degree of inhibition of positional exchange of the chlorine atoms in the P-Cl fragments known for the chlorine derivatives of pentacoordinated phosphorus atom. The obstacles to this dynamic process in the mentioned intramolecular dimers is shown to result from the spatial nonvalent interactions due to the short contacts of the chlorine and hydrogen atoms.     

Reaction of the novel Ru<Subscript>3</Subscript>(CO)<Subscript>10</Subscript>[Ph<Subscript>2</Subscript>P(CH<Subscript>2</Subscript>)<Subscript>2</Subscript>Si(OEt<Subscript>3</Subscript>)]<Subscript>2</Subscript> complex on SBA-15 and MCM-41 mesoporous silicas

The reaction of Ru₃(CO)₁₂ with 2(diphenylphosphino)ethyl-triethoxysilane (DPTS) in hydrocarbons, leads to the functionalized Ru₃(CO)_12−n [Ph₂P(CH₂)₂Si(OEt₃)] _n (n = 1,2) complexes. The complex with two phosphine substituents was chemically anchored on mesoporous silicas, SBA-15 and MCM-41, in order to obtain two hybrid materials characterized by a different localization of the metal centre on the surface of the porous supports. A detailed investigation of the cluster, before and after chemical anchoring on the mesoporous silicas, was pursued. Particular attention was also devoted to the study of the morphological, structural and textural properties of the metal-functionalised silicas (Ru/SBA-15 and Ru/MCM-41) by infrared spectroscopy (FT-IR), scanning electron microscopy, X-ray diffraction and N₂ physisorption analysis.     

Electron interactions in the (η<Superscript>2</Superscript>-C<Subscript>60</Subscript>)Pd[P(Ph<Subscript>2</Subscript>)C<Subscript>5</Subscript>H<Subscript>4</Subscript>]<Subscript>2</Subscript>Fe complex

The electronic structure of the (η²-C₆₀)Pd[P(Ph₂)C₅H₄]₂Fe complex was calculated by the “hybrid” B3LYP method. Comparison of the experimental X-ray emission C-Kα spectrum and theoretical spectrum of the compound demonstrated that the electron interactions between the C₆₀ core, palladium atom, and organometallic fragment are described correctly in the framework of the quantum chemical method used. The electronic structure of the organometallic fullerene complex can be presented as a set of blocks of orbitals corresponding to different types of chemical bond. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2640–2644, December, 2005.     

Synthesis and characterization of η<Superscript>3</Superscript>-allyl palladium(II) complexes with Ph<Subscript>2</Subscript>P(S)CHP(S)Ph<Subscript>2</Subscript> and OC(CF<Subscript>3</Subscript>)CHCO(C<Subscript>4</Subscript>H<Subscript>3</Subscript>S) co-ligands

The new complexes [(η³-Me₂CCMeCH₂)Pd{η²-Ph₂P(S)CHP(S)Ph₂] (1), [(η³-Me₂CCMeCH₂)Pd{η²-OC(CF₃) CHCO(C₄H₃S)}] (2) and [(η³-CH₂CMeCH₂)Pd{η²-OC(CF₃)CHCO(C₄H₃S)}] (3) have been synthesized by reacting [(η³-allyl)Pd(μ-Cl)]₂ with Ph₂P(S)CH₂P(S)Ph₂ and OC(CF₃)CH₂CO(C₄H₃S) in the presence of base. All have been characterized by elemental analysis, FT-IR, ¹H-n.m.r and FAB-mass spectroscopy. Spectroscopic studies suggest that both ligands are bidentate, forming six-membered Pd-S-P-C-P-S and Pd-O-C-C-C-O palladacycles, the η³-allyl group completing the coordination sphere.     

Kinetics and mechanisms of homogeneous catalytic reactions: Part 13. Regioselective reduction of quinoline catalysed by Rh(acac)(CO)[P(<Superscript>t</Superscript>Bu)(CH<Subscript>2</Subscript>CH=CH<Subscript>2</Subscript>)<Subscript>2</Subscript>]

The complex Rh(acac)(CO)[P(^tBu)(CH₂CH=CH₂)₂] (1) proved to be an efficient precatalyst for the regioselective hydrogenation of quinoline (Q) to 1,2,3,4-tetrahydroquinoline (THQ) under mild reaction conditions (125 °C and 4 atm H₂). A kinetic study of this reaction led to the rate law:

$$ r \, = \{ K_{1} k_{2} /(1 \, + \, K_{1} {\text{H}}_{ 2} )\} [{\text{Rh}}][{\text{H}}_{ 2} ]^{2} $$

which becomes

$$ r \, = \, K_{1} k_{2} [{\text{Rh}}][{\text{H}}_{ 2} ]^{2} $$

at hydrogen pressures below 4 atm. The active catalytic species is the cationic complex {Rh(Q)₂(CO)[P(^tBu)(CH₂CH=CH₂)₂]}⁺ (2). The mechanism involves the partial hydrogenation of one coordinated Q of (2) to yield a complex containing a 1,2-dihydroquinoline (DHQ) ligand, {Rh(DHQ)(Q)(CO)[P(^tBu)(CH₂CH=CH₂)₂]}⁺ (3), followed by hydrogenation of the DHQ ligand to give THQ and a coordinatively unsaturated species {Rh(Q)(CO)[P(^tBu)(CH₂CH=CH₂)₂]}⁺ (4); this reaction is considered to be the rate-determining step. Coordination of a new Q molecule to (4) regenerates the active species (2) and restarts the catalytic cycle.

     

High-temperature cubic modification of tetramethylammonium hexafluoridozirconate (N(CH<Subscript>3</Subscript>)<Subscript>4</Subscript>)<Subscript>2</Subscript>[ZrF<Subscript>6</Subscript>]

X-ray diffraction (XRD) and differential thermal analysis (DTA) methods are used to analyze tetramethylammonium hexafluoridozirconate of the composition [N(CH₃)₄]₂ZrF₆. In the temperature range between 96-110 °C, the crystals undergo a reversible phase transition from the low-temperature trigonal modification (space group R3 ) to the high-temperature cubic modification (space group Fm3m). The cubic phase is composed of regular [ZrF₆]²–octahedral and tetrahedral (CH₃)₄N⁺ cations linked by ionic interactions and the С–H???F hydrogen bonds.     

Structure and some properties of [UO<Subscript>2</Subscript>CrO<Subscript>4</Subscript>{CH<Subscript>3</Subscript>CON(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>}<Subscript>2</Subscript>]

A new complex [UO₂CrO₄{CH₃CON(CH₃)₂}₂] (I) was studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are monoclinic: a = 13.8108(11) Å, b = 8.6804(7) Å, c = 13.0989(10) Å, β = 104.777(1)°, V = 1518.4(2) ų, space group P2₁/c, Z = 4, R = 2.39%. The structure of I contains infinite chains of the [UO₂CrO₄{CH₃CON(CH₃)₂}₂] composition running along [001]; the complex belongs to the AT¹¹M¹ ₂ crystal-chemical group (A = UO ₂ ²⁺ , T¹¹ = CrO ₄ ^2? , M¹ = CH₃CON(CH₃)₂) of uranyl complexes. The chains are linked into a three-dimensional framework due to hydrogen bonds between oxygen atoms of chromate ions and hydrogen atoms of methyl groups of the dimethylacetamide.     

Crystal Structure of [UO<Subscript>2</Subscript>SO<Subscript>4</Subscript>{(CH<Subscript>3</Subscript>)HNCONH(CH<Subscript>3</Subscript>)}<Subscript>2</Subscript>]

The single crystals of [UO₂SO₄{(CH₃)HNCONH(CH₃)}₂] (I) were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 6.847(1) Å, b = 14.259(3) Å, c = 14.297(3) Å, β = 93.451(4)°, space group P2₁/n, Z = 4. The main structural units of crystals I are ribbons whose composition coincides with the composition of the compound. The crystal chemical formula of the complex is AT³M ₂ ¹ (A = UO ₂ ²⁺ ).     

Crystal structure of bis(semicarbazido)copper(II) nitrate [Cu(NH<Subscript>2</Subscript>NHC(O)NH<Subscript>2</Subscript>)<Subscript>2</Subscript>](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>

The crystal structure of bis(semicarbazido)copper(II) nitrate [Cu(NH₂NHC(O)NH₂)₂](NO₃)₂ has been studied by X-ray diffraction. Monoclinic crystals, a = 6.835(2) Å, b = 7.733(2) Å, c = 10.320(3) Å, β = 105.701(3)°, V = 525.1(2) ų, space group P2₁/c, Z = 2, d _msd = 2.136 g/cm³, μ(MoK _α) = 2.143 mm⁻¹. The structure was solved with the program for automatic analysis of Patterson’s function and refined by full-matrix least squares in an anisotropic approximation for all non-hydrogen atoms using 753 independent reflections; R ₁ = 0.0203. The square environment of the Cu atom is formed from the amino nitrogen atoms of the hydrazine fragments and the C=O oxygen atoms of the two semicarbazide bidentate molecules (Cu-N 1.928 Å, Cu-O 1.999 Å). The axial positions are occupied by the O atoms of the NO ₃ ⁻ outer-spheric anions (Cu-O 2.505 Å). In the structure, the complex cations and the NO ₃ ⁻ anions are linked into a framework by N-H...O type hydrogen bonds. Original Russian Text Copyright ? 2007 by G. V. Romanenko, Z. A. Savelieva, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 2, pp. 370–373, March–April, 2007.     

Molecular structure and conformational preferences of 1-chloro-1-silacyclohexane,CH<Subscript>2</Subscript>(CH<Subscript>2</Subscript>CH<Subscript>2</Subscript>)<Subscript>2</Subscript>SiH-Cl,as studies by gas-phase electron diffraction and quantum chemistry

The molecular structure of axial and equatorial conformer of the 1-chloro-1-silacyclohexane molecule, CH₂(CH₂CH₂)₂SiH-Cl, as well as thermodynamic equilibrium between these species were investigated by means of gas-phase electron diffraction and quantum chemistry on the MP2(full)/AUG-cc-PVTZ level of theory. According to electron diffraction data, the compound exists in the gas-phase as a mixture of conformers possessing the chair conformation of the six-membered ring and Cs symmetry and differing in the axial and equatorial position of the Si-Cl bond at 352 K. NBO analysis revealed that axial conformer of 1-chloro-1-silacyclohexane molecule is an example of the stabilization of the form that is unfavorable from the point of view steric effects and effects of conjugations and that stabilization is achieved due to electrostatic interactions.     

Phase equilibriums,ion association,and mechanisms of solvation in the LiN(CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>)<Subscript>2</Subscript>-(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>SO<Subscript>2</Subscript> system

The phase diagrams, isotherms of the electrical conductivity, Raman spectra, and time correlation functions of vibrational dephasing are studied for the LiN(CF₃SO₂)₂-(CH₃)₂SO₂ system, which is promising for use as an electrolyte in medium-temperature lithium-ion batteries. The phase diagram of this system contains a broad supercooled region. It is shown that the concentration dependences of the electrical conductivity are typical for solutions of strong electrolytes. The Raman spectra and the time correlation functions of vibrational dephasing for the anion and the solvent indicate that in the supercooling range, cations are weakly solvated by solvent molecules and form ion pairs.     

Complexes of podand-containing bis(dithiophosphonate) ligands with cobalt(II), nickel(II) and cadmium(II): recognition of CH<Subscript>2</Subscript>Cl<Subscript>2</Subscript>

Reaction of the potassium salts of podand-containing bis(dithiophosphonate)s [PhO(4-C₆H₄)P(S)(SH)OCH₂CH₂]₂O (H ₂ L) with Co(II), Ni(II) and Cd(II) in aqueous EtOH leads to complexes of formulae M₂(L-S,S′)₂. The structural formulae of the compounds were deduced by physico-chemical and spectroscopic methods. It was established that complex Ni ₂ L ₂ recognizes CH₂Cl₂.     

Structures and mutual transformations of isomers of germylium ions (CH<Subscript>3</Subscript>)H<Subscript>2</Subscript>Ge<Superscript>+</Superscript> and (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>HGe<Superscript>+</Superscript> and their silicon analogs

The potential energy surfaces of the (CH₃)_nH_3?n M⁺ ions, where n = 1, 2; M = Si, Ge, were scanned using the B3LYP method with 6–31G* and aug-cc-pVDZ basis sets. The major attention was given to isomeric species having the form of complexes of the HM⁺ and CH₃M⁺ ions with hydrogen, methane, and ethane molecules. These species were characterized previously neither by experimental nor by theoretical methods. It was found that these species become more stable in going from Si to Ge; the complex [CH₃Ge⁺CH₄] is the second isomer in the energy after (CH₃)₂HGe⁺. However, the heights of the activation barriers to formation of these complexes from the most stable isomer, though decreasing in going from Si to Ge, remain relatively high and, what is particularly important, somewhat exceed the activation barrier to formation of the complex [H₃Ge⁺·C₂H₄].