Characterization by theory of H-transfers and onium reactions of CH<Subscript>3</Subscript>CH<Subscript>2</Subscript>CH<Subscript>2</Subscript>N<Superscript>+</Superscript>H=CH<Subscript>2</Subscript>

H-transfers by 4-, 5-, and 6-membered ring transition states to the pi-bonded methylene of CH3CH2CH2NH+=CH2 (1) are characterized by theory and compared with the corresponding transfers in cation radicals. Four-membered ring H-transfers converting 1 to CH3CH2CH=N+HCH3 (2) and CH3N+H=CH2 to CH2=NH+CH3 are high-energy processes involving rotation of the source and destination RHC= groups (R = H or C2H5) to near bisection by skeletal planes; migrating hydrogens move near these planes. The H-transfer 1 --> CH3C+HCH2NHCH3 (3) has a higher energy transition-state than 1 --> 2, in marked contrast to the corresponding relative energies of 4- and 5-membered ring H-transfers in cation-radicals. Six-membered ring H-transfer-dissociation (1 --> CH2=CH2 + CH2=N+HCH3) is a closed shell analog of the McLafferty rearrangement. It has a lower energy transition-state than either 1 --> 2 or 1 --> 3, but is still a much higher energy process than 6-membered ring H-transfers in aliphatic cation radicals. In contrast to the stepwise McLafferty rearrangement in cation radicals, H-transfer and CC bond breaking are highly synchronous in 1 --> CH3N+H=CH2 + CH2=CH2. H-transfers in propene elimination from 1 are ion-neutral complex-mediated: 1--> [CH3CH2CH2+ ---NH=CH2] --> [CH3C+HCH3 NH=CH2] --> CH3CH = CH2 + CH2=NH2+. Intrinsic reaction coordinate tracing demonstrated that a slight preference for H-transfer from the methyl containing the carbon from which CH2=NH is cleaved is due to CH2=NH passing nearer this methyl than the other on its way to abstracting H, i.e., some memory of the initial orientation of the partners accompanies this reaction.     

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].     

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.     

Titanium tetrafluoride complexation with phosphorylated ketone Ph<Subscript>2</Subscript>P(O)(CH<Subscript>2</Subscript>)<Subscript>2</Subscript>C(O)Me in CH<Subscript>2</Subscript>Cl<Subscript>2</Subscript>

The products resulting from the reaction of TiF₄ with Ph₂P(O)(CH₂)₂C(O)Me (L') in CH₂Cl₂ have been studied by ¹⁹F{¹H} and 31P{¹H} NMR spectroscopy. At a twofold excess of L', solution contains cis-TiF₄(L')2 (>90%), trans-TiF₄(L')₂, and fac-[TiF₃L₃']⁺, where L' is coordinated via the P=O group, as well as the dimer [(Ti₂F₇L'₂)₂]+, where L' is coordinated through the P=O and C=O groups. An equimolar solution contains dimeric and polynuclear complexes containing moieties with three terminal cis fluorine ions, while the other coordination sites are occupied by the P=O groups and F^– bridges. At a twofold excess of TiF₄, ligand L' coordinates via the P=O and C=O groups and behaves as a bridge along with F^– ions. Thermodynamic stability of the structures of the TiF₄L'₂ isomers and the structure of [(µ-F)(µ-L')₂(TiF₃)₂]⁺ has been calculated.     

Kinetics and mechanisms of homogeneous catalytic reactions. Part 3. Regioselective,catalysed [RuH(CO)(NCMe)2(PPh3)2]BF4 reduction of quinoline

Summary A kinetic study of the regioselective homogeneous hydrogenation of quinoline (Q) to 1,2,3,4-tetrahydroquinoline (THQ) was carried out using the cationic complex [RuH(CO)(NCMe)₂(PPh₃)₂]BF₄ (1) as the precatalyst. The experimentally determined rate law wasr = {k ₂ K ₁/(1+K ₁[H₂])}[Ru₀][H₂]², which becomesr = {k ₂ K ₁[Ru₀]–[H₂]² at low hydrogen concentrations (k ₂ K ₁ = 28.5M ^–2 s^–1 at 398 K). The corresponding activation parameters were found to be H = 42 + 6 kJ mol^–1, S = – 115 ± 2JK^–1mol^–1 and G = 92 ± 8 kJ mol^–1. Complex(1) was found to react with Q in CHCl₃ under reflux to yield [RuH(CO)(NCMe)(N-Q)(PPh₃)₂]BF₄ (2) which was also isolated from the hydrogenation runs. These experimental findings, together with the results ofab initio self-consistent-field molecular orbital calculations on the free organic molecules involved, are consistent with a mechanism involving a rapid and reversible partial hydrogenation of(2) to yield the corresponding dihydroquinoline (DHQ) species [RuH(CO)(NCMe)(DHQ)(PPh₃)₂]BF₄ (4), followed by a rate-determining second hydrogenation of DHQ to yield [RuH(CO)(NCMe)(THQ)(PPh₃)₂]BF₄ (3).     

Structure of heteroassociates formed in the HF-(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>CO binary liquid system

The vibrational spectra of a series of HF solutions in acetone (1:20–8.9:1) are analyzed with the help of special techniques. It is shown that three types of strong heteroassociates (HAs) with 1:1, 4:1, and ≥10:1 stoichiometric ratios of the molecules are formed in the HF-(CH₃)₂CO binary liquid system. The concentration ranges of the existence of HAs in the solution and the stretching vibrational frequency of their constituent HF molecules are estimated. The density functional method (B3LYP/6-31++G(d,p)) is used to calculate the optimal configurations and IR spectra of the (HF) _m ·((CH₃)₂CO) _n molecular complexes (m = 1, 2, 4, 8, n = 1, 2) of different structure. The relative stability of the latter is studied. By comparing the calculated and experimental data, the composition (2:2 and 4:1) and structure of two types of HAs are determined.     

Elimination of H<Subscript>2</Subscript> from CH<Subscript>3</Subscript>CH=N<Superscript>+</Superscript>HCH<Subscript>3</Subscript>: A synchronous,concerted 1,4-H<Subscript>2</Subscript> elimination

Most H2 eliminations from cations in the gas phase are formally 1,1- or 1,2- processes. Larger ring size H2 eliminations are rare and little studied. Thus, whether the 6-center, 1,4- elimination CH3CH=N+HCH3-->CH2=CHN+H=CH2+H2 is concerted and synchronous, as indicated by isotope effects and predicted by conservation of orbital symmetry, is a significant question. This reaction is characterized here by application of QCI and B3LYP theories. CH bond-breaking and H-H bond-making in this reaction are found by theory to be highly synchronized, consistent with previously established isotope effects and in contrast to "forbidden" 1,2-eliminations from organic cations in the gas phase. This reaction is made feasible by its conservation of orbital symmetry, the energy supplied by formation of the H-H bond, and a favorable geometry of the ion for eliminating H2.     

Theoretical study on the reaction mechanism of (CH<Subscript>3</Subscript>)<Subscript>3</Subscript>CO<Superscript>.</Superscript> radical with NO

The reaction mechanism of (CH₃)₃CO^. radical with NO is theoretically investigated at the B3LYP/6-31G* level. The results show that the reaction is multi-channel in the single state and triplet state. The potential energy surfaces of reaction paths in the single state are lower than that in the triple state. The balance reaction: (CH₃)₃CONO⇔(CH₃)₃CO^.+NO, whose potential energy surface is the lowest in all the reaction paths, makes the probability of measuring (CH₃)₃CO^. radical increase. So NO may be considered as a stabilizing reagent for the (CH₃)₃CO^. radical.     

Crystal structure of two polymorphs of molybdenyl salicylidene-2-furfuriliminate (HL<Superscript>1</Superscript>) [MoO<Subscript>2</Subscript>(L<Superscript>1</Superscript>)<Subscript>2</Subscript>]

The crystal structures of two polymorphs of molybdenyl salicylidene-2-furfuryliminate [MoO₂(L¹)₂] have been solved by X-ray diffraction. Both complexes crystallize in centrosymmetric and non-centrosymmetric space groups (P2₁/c and Р2₁, respectively) of monoclinic system and have similar structures and close geometric parameters. The Мо atoms have a distorted octahedral coordination to two terminal oxo ligands in cis-positions to each other and two pairs of the oxygen atoms (cis- to О(oxo)) and the nitrogen atoms (trans- to О(oxo)) of two bidentate chelate ligands (L¹)^–.     

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.     

Arene complexes [(η-C<Subscript>5</Subscript>H<Subscript>5</Subscript>)M(η-C<Subscript>6</Subscript>R<Subscript>6</Subscript>)]<Superscript>2+</Superscript> (M = Rh,Ir)

The dicationic arene complexes [CpM(arene)](BF₄)₂ (arene = C₆H₆, 1,3,5-C₆H₃Me₃, or C₆Me₆) were synthesized by the reactions of the solvated complexes [CpM(MeNO₂)₃](BF₄)₂ (M = Rh, Ir) with benzene and its derivatives. The solvated complexes were generated in situ by abstraction of I^– from [CpMI₂]₂ with AgBF₄. A procedure was developed for the synthesis of the iodide [CpRhI₂]₂ based on the reaction of the cyclooctadiene derivative CpRh(1,5-C₈H₁₂) with I₂. The structure of the [CpRh(C₆Me₆)](BF₄)₂ complex was established by X-ray diffraction analysis.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1871–1874, September, 2004.     

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⁺ ).     

Complex amidoboranes M<Superscript>2</Superscript>[M<Superscript>1</Superscript>(NH<Subscript>2</Subscript>BH<Subscript>3</Subscript>)<Subscript>4</Subscript>] (M<Superscript>1</Superscript> = Al,Ga; M<Superscript>2</Superscript> = Li,Na, K,Rb, Cs)

Structural, spectral, and thermodynamic characteristics of complex amidoboranes M²[M¹(NH₂BH₃)₄] (M¹ = Al, Ga; M² = Li, Na, K, Rb, Cs) were calculated by the B3LYP/def2-SVPD quantum-chemical method. The procedure for the synthesis of these compounds by reactions of alkali metal amidoboranes with aluminum and gallium chlorides was suggested and experimentally tested. Reaction products were characterized by the NMR and IR spectroscopy and X-ray phase analysis.     

Complex salts with participation of [Rh(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>]<Superscript>3+</Superscript> cations

Four complex salts with the polyatomic [Rh(NH₃)₆]³⁺ cation are synthesized and studied by X-ray diffraction. The crystallographic characteristics of [Rh(NH₃)₆](WO₄)Cl are determined and the structures of [Rh(NH₃)₆]Cl₃, [Rh(NH₃)₆](ReO₄)₃·2H₂O, and [Rh(NH₃)₆](MoO₄)Cl·3H₂O are solved. The features of mutual packing of the fragments are studied.     

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.     

X-ray diffraction study of [M<Superscript>I</Superscript>(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl] [M<Superscript>II</Superscript>Br<Subscript>6</Subscript>] (M<Superscript>I</Superscript> = Rh,Ir; M<Superscript>II</Superscript> = Re,Ir) polycrystals

Based on the X-ray diffraction data for polycrystals, the crystal structures of double complex salts [Rh(NH₃)₅Cl][ReBr₆] and [Ir(NH₃)₅Cl][ReBr₆] are refined. The structure of [Rh(NH₃)₅Cl][IrBr₆] is determined. Initial models are constructed using the Monte Carlo method in the straight space. Further refinement is made by the Rietveld method. It is shown that such an approach is suitable for the refinement of crystal structures composed of isolated rigid polyhedra and can be used to determine the structure of salts without structural analogues     

Synthesis and crystal structure of [Co(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>][AuX<Subscript>4</Subscript>]X<Subscript>2</Subscript> (X = Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>)

[Co(NH₃)₆][AuX₄]X₂ binary complex salts, where X = Cl^? (I) and Br^? (II), have been obtained and defined by element, X-ray diffraction, and thermal analyses and by IR, Raman, and electron spectroscopy. The compounds are isostructural. Their structural units are the [Co(NH₃)₆]³⁺ complex cations, the [AuX₄]^? complex anions, and the X^? anions. The plane square environment of the gold atom is completed to an elongated bipyramid by two halide ions lying at distances Au...Cl 3.245 Å for I and Au...Br 3.362 Å for II. The thermolysis products of I and II are pure gold and cobalt metal powders when thermolysis is performed under hydrogen and a mixture of metallic gold with cobalt halide in a reaction under an inert atmosphere.     

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.