Synthesis and Structure of a 2, 8, 9‐Trioxa‐3, 5, 7‐trisila‐1‐titanaadamantane

The title compound has been prepared from [Ti(η⁵‐C₅Me₅)Cl₃] and cis‐cis‐(t‐BuSi(OH)—CH₂)₃ in hexane solution in the presence of Et₃N. The pale yellow complex was characterized by NMR and MS spectra, as well as by a crystal structure determination. The two crystallographic independent molecules in the triclinic unit cell (space group P1¯, No. 2, Z = 4) both have a nearly identical adamantane‐like TiO₃Si₃C₃ cage of approximate C_3v symmetry. The exocyclic C—C—C bond angles in the Cp‐ligand range from 123° to 129°. A quantum chemical calculation of the free molecule predicts this range to be 124° to 127°. The arrangement of the molecules in the crystal is characteristic for an offset face‐to‐face ππ stacking of the aromatic η⁵‐C₅Me₅ rings.     

A mass spectral study of 1-(aryldimethylsilyl)-2-propanones and their isomeric 2-(aryldimethylsiloxy)-1-propenes

The mass spectra of a series of β-ketosilanes, p-Y? C₆H₄Me₂SiCH₂C(O)Me and their isomeric silyl enol ethers, p-Y? C₆H₄Me₂SiOC(CH₃)?CH₂, where Y = H, Me, MeO, Cl, F and CF₃, have been recorded. The fragmentation patterns for the β-ketosilanes are very similar to those of their silyl enol ether counterparts. The seven major primary fragment ions are [M? Me·]⁺, [M? C₆H₄Y·]⁺, [M? Me₂SiO]⁺˙, [M? C₃H₄]⁺˙, [M? HC?CCF₃]⁺˙, [Me₂SiOH]⁺˙ and [C₃H₆O]⁺˙ Apparently, upon electron bombardment the β-ketosilanes must undergo rearrangement to an ion structure very similar to that of the ionized silyl enol ethers followed by unimolecular ion decompositions. Substitutions on the benzene ring show a significant effect on the formation of the ions [M? Me₂SiO]⁺˙ and [Me₂SiOH]⁺˙, electron donating groups favoring the former and electron withdrawing groups favoring the latter. The mass spectral fragmentation pathways were identified by observing metastable peaks, metastable ion mass spectra and ion kinetic energy spectra.     

Lanthanide versus Actinide Reactivity in the Formation of Sterically Crowded [(C5Me5)3MLn] Nitrile and Isocyanide Complexes

The limits of steric crowding in organometallic metallocene complexes have been examined by studying the synthesis of [(C₅Me₅)₃ML_n] complexes as a function of metal in which L=Me₃CCN, Me₃CNC, and Me₃SiCN. The bis(tert‐butyl nitrile) complexes [(C₅Me₅)₃Ln(NCCMe₃)₂] (Ln=La, 1 ; Ce, 2 ; Pr, 3 ) can be isolated with the largest lanthanide metal ions, La³⁺, Ce³⁺, and Pr³⁺. The Pr³⁺ ion also forms an isolable mono‐nitrile complex, [(C₅Me₅)₃Pr(NCCMe₃)] ( 4 ), whereas for Nd³⁺ only the mono‐adduct [(C₅Me₅)₃Nd(NCCMe₃)] ( 5 ) was observed. With smaller metal ions, Sm³⁺ and Y³⁺, insertion of Me₃CCN into the M? C(C₅Me₅) bond was observed to form the cyclopentadiene‐substituted ketimide complexes [(C₅Me₅)₂Ln{NC(C₅Me₅)(CMe₃)}(NCCMe₃)] (Ln=Sm, 6 ; Y, 7 ). With tert‐butyl isocyanide ligands, a bis‐isocyanide product can be isolated with lanthanum, [(C₅Me₅)₃La(CNCMe₃)₂] ( 8 ), and a mono‐isocyanide product with neodymium, [(C₅Me₅)₃Nd(CNCMe₃)] ( 9 ). Silicon–carbon bond cleavage was observed in reactions between [(C₅Me₅)₃Ln] complexes and trimethylsilyl cyanide, Me₃SiCN, to produce the trimeric cyanide complexes [{(C₅Me₅)₂Ln(μ‐CN)(NCSiMe₃)}₃] (Ln=La, 10 ; Pr, 11 ). With uranium, a mono‐nitrile reaction product, [(C₅Me₅)₃U(NCCMe₃)] ( 12 ), which is analogous to 5 , was obtained from the reaction between [(C₅Me₅)₃U] and Me₃CCN, but [(C₅Me₅)₃U] reacts with Me₃CNC through C? N bond cleavage to form a trimeric cyanide complex, [{(C₅Me₅)₂U(μ‐CN)(CNCMe₃)}₃] ( 13 ).     

Reactivity of functional groups toward H+ and SiMe3 + ions

No correlation was observed between the gas-phase basicities of various functional groups toward H⁺ and SiMe₃ ⁺ ions. Differences in the reactivity of functional groups studied toward SiMe₃ ⁺ ions are smaller than those in the reactivity toward protons. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 565–567, March, 2000.     

Stabilization of Linear C3 by Two Donor Ligands: A Theoretical Study of L-C3-L (L=PPh3, NHCMe,cAACMe)**

Quantum chemical studies using density functional theory and ab initio methods have been carried out for the molecules L-C₃-L with L=PPh₃ ( 1 ), NHC^Me ( 2 , NHC=N-heterocyclic carbene), and cAAC^Me ( 3 , cAAC=cyclic (alkyl)(amino) carbene). The calculations predict that 1 and 2 have equilibrium geometries where the ligands are bonded with rather acute bonding angles at the linear C₃ moiety. The phosphine adduct 1 has a synclinal (gauche) conformation whereas 2 exhibits a trans conformation of the ligands. In contrast, the compound 3 possesses a nearly linear arrangement of the carbene ligands at the C₃ fragment. The bond dissociation energies of the ligands have the order 1 < 2 < 3 . The bonding analysis using charge and energy decomposition methods suggests that 3 is best described as a cumulene with electron-sharing double bonds between neutral fragments (cAAC^Me)₂ and C₃ in the respective electronic quintet state yielding (cAAC^Me)=C₃=(cAAC^Me). In contrast, 1 and 2 possess electron-sharing and dative bonds between positively charged ligands [(PPh₃)₂]⁺ or [(NHC^Me)₂]⁺ and negatively charged [C₃]⁻ fragments in the respective doublet state.     

Gas phase reactions of the ion C5H5Fe+: A kinetic study

The kinetics of gas phase reactions of the ion C₅H₅Fe⁺ with oxygen (Me₂CO, Me₂O, MeOH, iso-propanol, H₂O) and nitrogen (NH₃, NH₂Me, NHMe₂, NMe₃) donor ligands have been studied by ion trap mass spectrometry. While in the literature reactions of the ion Fe⁺, with the same ligands, the principal reaction path involves fragmentation in almost all the reactions of the ion C₅H₅Fe⁺, formation of adduct ions is the major reaction path. The reactivity of these two ions is briefly compared in the ion trap conditions. Kinetic data for the ion C₅H₅Fe⁺ indicate that the reactions show a large range of efficiency and a linear correlation is found between the log of the reaction rate constants and the ionization energy of ligands with the same donor atom.     

Reactions of silylium ions with nucleophiles

Transformation of the diethylsilylium cation Et₂Si⁺H into ethyl-and dimethylsilylium ions EtSi⁺H₂ and Me₂Si⁺H in reactions with nucleophiles is induced by electron-donor compounds. Their activity increases in the order Bu₂O < BuOH < (Me₃Si)₂O < C₆H₆ and is determined by the structure of the intermediate adduct and electron density distribution in it. Qualitative estimation shows that the affinity of the tritiated diethylsilylium cation Et₂Si⁺T for a nucleophile increases in the order C₆H₆ < BuOH < Bu₂O < (Me₃Si)₂O. The higher affinity of the Et₂Si⁺H cation for hexamethyldisiloxane compared to dibutyl ether, at similar basicity of the nucleophiles, is attributable to the higher charge of the oxygen atom in (Me₂Si)₂O.     

Chemical ionization mass spectrometry of halogenoalkanes with tetramethylsilane as reagent gas

Chemical ionization mass spectra of halogenoalkanes (RX) obtained using tetramethylsilane as reagent gas show two major peaks corresponding to the cluster ion RX⁺SiMe₃ and alkyl ion R⁺. Iodides exhibit the highest affinity toward the trimethylsilyl ion and produce the most stable silylated molecular ions, whereas bromides and especially chlorides are less reactive toward Me₃Si⁺ ions and form less stable [M + SiMe₃]⁺ ions.     

The nature of ion exchange selectivity of phenol-formaldehyde sorbents with respect to cesium and rubidium ions

The structure of aqua complexes of alkali metal ions Me⁺(H₂O) _n , n = 1−6, where Me is Li, Na, K, Rb, and Cs, and complexes of 2,6-dimethylphenolate anion (CH₃)₂PhO⁻ selected as a model of the elementary unit of phenol-formaldehyde ion exchanger with hydrated alkali metal cations Me⁺(H₂O) _n , n = 0−5, was studied by the density functional method. The energies of successive hydration of the cations and the energies of binding of alkali metal hydrated cations with (CH₃)₂PhO⁻ depending on the number of water molecules n were calculated. It was shown that the dimethylphenolate ion did not have specific selectivity with respect to cesium and rubidium ions. The energies of hydration and the energies of binding of alkali metal cations with (CH₃)₂PhO⁻ decreased in the series Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺ as n increased. The conclusion was drawn that the reason for selectivity of phenol-formaldehyde and other phenol compounds with respect to cesium and rubidium ions was the predomination of the ion dehydration stage in the transfer from an aqueous solution to the phenol phase compared with the stage of binding with ion exchange groups.     

[C6H6, C3H7 +]and [C6H7 +, C3H6] ion-neutral complexes intermediate in the reactions of protonated propylbenzenes

From the mass-analysed ion kinetic energy spectra of labelled ions, kinetic energy releases and thermodynamic data, it is proved that protonated n-propylbenzene (1) isomerizes into protonated isopropyl benzene (2). It is also shown that the dissociation of the less energetic metastable ions of (2), leading to [iso-C₃H₇]⁺ and [C₆H₇]⁺ product ions, is preceded by H exchange. This H exchange involves two interconverting ion-neutral complexes [C₆H₆, iso-C₃H₇⁺] (2π) and [C₆H₇⁺, C₃H₆] (2α).     

Synthese und Kernresonanzspektren von Methylphenyl-substituierten Trisilylphosphanen PSi3 Me n Ph 9−n

Trisilylphosphanes of the type PSi₃ Me _x Ph _9–x are formed when sodium/potassiumphosphide reacts with methylphenylchlorosilanesMe _n Ph _3–n SiCl or with mixtures of methylphenylchlorosilanes. The phosphanes (SiMe ₃) _n P (SiMe _m Ph _3–m )_3–n (n, m=0, 1, 2, 3) were separated and purified by destillation or crystallization and their²⁹Si as well as³¹P-NMR-spectra were recorded.

     

Differences Between Gas-Phase and Solid-State Molecular Structures of the Simplest Phosphonium Ylide,Me3P=CH2

Clearly different from local C ₃ symmetric is the heavy-atom core of Me₃P=CH₂, the simplest phosphonium ylide. The geometry obtained by reanalysis of gas-electron-diffraction data from 1977 is now consistent with theoretical calculations, but different from the molecular structure in the solid state. The picture shows the structure of Me₃P=CH₂ in the gas phase (a) and in the crystal (c) together with the calculated transition state (b) (viewed along the P=C bond).     

The Reaction of Bunsen's Cacodyl Disulfide,Me2As(S)‐S‐AsMe2, with Iodine: Preparation and Properties of Dimethylarsinosulfenyl Iodide,Me2As‐S‐I

Bunsen's cacodyl disulfide, Me₂As(S)‐S‐AsMe₂ ( 1 ), reacted with iodine giving the novel dimethylarsinosulfenyl iodide, Me₂As‐S‐I ( 3 ) although theoretical calculations indicated that the As^V compound Me₂As(S)‐I ( 4 ) was more stable in the gas phase. The oily product was stable neat and as a solution in CDCl₃ at +4 °C and –20 °C for at least 15 d. Light, H₂O, H₂O₂, and Zn dust, but not NaI or Ag, decomposed it. Compound 3 did not interact with Ph₃N, with Ph₂NH and PhNH₂ it interacted but not reacted. 3 was decomposed by piperidine, with pyridine and 4‐dimethylaminopyridine it interacted and produced Me₂As‐SS‐AsMe₂ ( 2 ) and I₂ that formed charge transfer complexes Base · I₂, whereas Et₃N decomposed 3 , and 3Et₃N · 2I₂ was isolated. 3 was desulfurized by Ph₃P and (Me₂N)₃P completely, and by (PhO)₃P and (PhS)₃P partially. The reactions of 3 with (Me₂N)₃P, (PhS)₃P, and (EtO)₃P were complicated. From the As^III nucleophiles, only Ph₃As was bound, while (PhS)₃As reacted slowly in a complicated manner with 3 . No interaction of 3 with MeOH or PhOH was observed but NaOH, Ag₂O, and PhONa decomposed it. Thiophenol produced traces of Me₂As‐SPh ( 10 ) and sodium thiophenolate attacked mainly at As^III of 3 . Thus, externally stabilized sulfenium ions of the type Me₂As‐S‐Nu⁺I^– were not obtained.     

GASEOUS DIPHOSPHORUS AND TRIPHOSPHORUS SULFIDE: GENERATION AND IDENTIFICATION BY NEUTRALIZATION-REIONIZATION MASS SPECTROMETRY

Abstract

The dissociative ionization by electron impact (70 eV) of tetraphosphorus trisulfide, P₄S₃, yields [P₃S]⁺ and [P_ZS]⁺⁰ ions whose structures have been investigated by means of Coliisionai Activation (CA) mass spectra. Using the technique of Neutralization-Reionization mass spectrometry (NRMS) it is shown that both ions can be reduced to the corresponding neutral molecules. Thus, triphosphorus sulfide and diphosphorus sulfide are viable molecules in the rarefied gas phase. The results of ab initio MO calculations were used to interpret the experimental findings. Tetrahedral (C_3v) and triangular (C_2v) structures are proposed for the [P,S]⁺ and [P_ZS]⁺⁰ ions respectively.     

Theoretical and Experimental Study of Complex Ions from Reactions of Al+ (Cu+) with Amine Molecules

The gas phase reactions of metal ions (Al⁺, Cu⁺) with amine molecules [CH₃NH₂=MA, (CH₃)₂NH=DMA] were investigated using a laser ablation‐molecular beam method. The directly associated product complex ions,Al⁺‐MA and Al⁺‐DMA, and the dehydrogenation product ions, Cu⁺(CH₂NH) and Cu⁺(C₂H₅N), as well as hydrated ion Cu⁺(NC₂H₅·H₂O), have been obtained and recorded from the reactions of the metal ions and organic amine molecules, and density functional theory (B3LYP) calculations have been performed to reveal the optimized geometry, energetics, and reaction mechanism of the title reactions with basis set 6‐311+G(d,p) adopted.     

Surface characterization and thermodynamics of adsorption of Sr2+, Ce3+, Sm3+, Gd3+, Th4+, UO 2 2+ on activated charcoal from aqueous solution

Surface parameters of the activated charcoal were measured using precise instrumental techniques for dehydration, carbon content, trace metals impurities, anions, bulk, tap and true densities, surface area, pore volume, porosity and average particle diameter. The adsorption of Sr²⁺, Ce³⁺, Sm³⁺, Gd³⁺, Th⁴⁺ and UO ₂ ²⁺ ions on activated charcoal from aqueous solution was studied as a function of temperature. Thermodynamic parameters such as HH ⁰ and S ⁰ were calculated from the slopes and intercepts of the linear variation of lnK ₁ vs. 1/T, whereK ₃ is obtained from Langmuir equation. The results show endothermic heats of adsorption, but negative free energy values indicate that the adsorption process of metal ions on activated charcoal is favored at high temperature. The value of isosteric heat of adsorption, calculated from the Clausius-Clapeyron equation, shows that the surface of the activated charcoal is heterogeneous with respect to activity. A wavelength dispersive x-ray fluorescence spectrometer was used for measuring the concentration of metal ions.     

Electronic effects of Me3SiOCR2 substituents in acetylene derivatives

The σR⁰ and σ_p parameters of Me₃SiOCR₂ and HOCR₂ substituents at the triple bond were determined using the IR spectra of individual acetylene derivatives and their H-complexes. These parameters vary as the effective charge on the atoms of the C≡C fragment of terminal acetylenic alcohols and their trimethylsilyl ethers changes due to intermolecular interaction. The most reliable values of σR⁰ and σ_p parameters (−0.02 and −0.03, respectively) for the Me₃SiOCH₂ substituent were established; they indicate a sharp decrease in σ,π-conjugation of the Me₃SiOCH₂ substituent with the triple bond as compared to the Me₃SiCH₂ substituent. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1759–1762, September, 1998.     

Bildung siliciumorganischer Verbindungen. 110. Reaktionen von (Cl3Si)2CCl2, seiner Si-methylierten Derivate,von (Cl3Si)2CHCl, (Cl3Si)2C(Cl)Me und Me2CCl2 mit Silicium (Cu-Kat.)

Formation of Organosilicon Compounds. 110. Reactions of (Cl₃Si)₂CCl₂ and its Si-methylated Derivatives as well as of (Cl₃Si)₂CHCl, (Cl₃Si)₂C(Cl)Me and Me₂CCl₂ with Silicon (Cu cat.) The reactions of (Cl₃Si)₂CCl₂ 1 , its Si-methylated derivatives (Me₃Si)₂CCl₂ 8 , Me₃Si? CCl₂? SiMe₂Cl 9 , (ClMe₂Si)₂CCl₂ 10 , Me₃Si? CCl₂? SiMeCl₂ 11 , Cl₂MeSi? CCl₂? SiCl₃ 12 as well as of (Cl₃Si)₂CHCl 38 , (Cl₃Si)₂CClMe 39 and of Me₂CCl₂ with Si (Cu cat.) in a fluid bed reactor ( 38 and 39 also in a stirred solid bedreactor) arc presented. While (Cl₃Si)₂CCl₂ 1 yields C(SiCl₃)₄ 2 the 1,1,3,3-tetrachloro-2,2,4,4-tetrakis(trichlorsilyl)-1,3-disilacyclobutane Si₆C₂Cl₁₆ 3 and the related C-spiro linked disilacyclobutanes Si₈C₃Cl₂₀ 4 , Si₁₀C₄Cl₂₄ 5 , Si₁₂C₅Cl₂₈ 6 , Si₁₄C₆Cl₃₂ 7 this type of compounds is not obtained starting from the Si-methylated derivatives 8, 9, 10, 11 They Produce a number of variously Si-chlorinated and -methylated tetrasila- and trisilamethanes. However, Cl₂MeSi? CCl₂? SiCl₃ 12 forms besides of Si-chlorinated trisilamethanes also the disilacyclobutanes Si₆C₂Cl₁₅Me 34 and cis- and trans Si₆C₂Cl₁₄Me₂ 35 as well as the spiro-linked disilacyclobutanes Si₈C₃Cl₁₉Me 36 , Si₈C₃Cl₁₈Me₂ 37 . (Cl₃Si)₂CHCl 38 mainly yields HC(SiCl₃)₃ 31 and also the disilacyclobutanes cis- and trans-(Cl₃Si)HC(SiCl₂)₂CH(SiCl₃) 41 and (Cl₃Si)₂C(SiCl₂)₂CH(SiCl₃) 45 the 1,3,5-trisilacyclohexane [Cl₃Si(H)C? SiCl₂]₃ 44 as well as [(Cl₃Si)₂CH]₂SiCl₂, and (Cl₃Si)₂CClMe 39 mainly yields (Cl₃Si)₂C?CH₂and (Cl₃Si)₂besides of HC(SiCl₃)₃, MeC(SiCl₃)₃and (Cl₃Si)₃C? SiCl₂Me.,. Me₂CCl₂ 59 mainly yields Me(Cl)C?CH₂, Me₂CHCl and HCl₂Si? CMe₂? SiCl₃, besides of Me₂C(SiCl₃)₂ and Me₂C(SiCl₂H)₂ Compound 3 crystallizes triclinically in the space group P1 (Nr. 2) mit a = 900,3, b = 914,0, c = 855,3 pm, α = 116,45°, β = 101,44°, γ = 95,86° and one molecule per unit cell. Compound 4 crystallizes monoclinically in thc space group C2/c (no. 15) with a = 3158.3,b = I 103.7, c = 2037.4 pm, β = 1 16.62° and 8 molecules pcr unit cell. The disilacyclobutane ring of compound 3 is plane, showing a mean distance of d (Si-C) =19 1.8 pm and the usual deformations of endocyclic angles: α_Si = 94,2°> 85,8° = α_C.The spiro-linked disilacyclobutane rings of compound 4 are slightly folded by a mean angle of (19.0°). Their mean distances were found to be d (Si? C) = 190.4 pm relating to the central carbon atom and 192.0 pm to the outer ones, respectively. The deformations of endocyclic angles: α_Si = 93,9°> 84,4° = α_C are comparable to those of compound 3.     

Interaction of the trimethylsilyl cation with molecules of aliphatic nitro compounds in the gas phase

Interaction of mononitroalkanes with the trimethylsilyl cation in the gas phase under chemical ionization (CI) conditions results in the formation of [M+SiMe₃]⁺ ions, which are more stable than the corresponding protonated molecular ions. In the case of 2-nitro-2-methylpropane and 2-nitropentane, fragmentation of the [M+SiMe₃]⁺ ions occurs with the formation of C₄H₉ ⁺ and C₅H₁₁ ⁺ carbocations, respectively. In the case of 1,1-dinitroethane and 1-halo-1,1-dinitroethane, fragmentation of the [M+SiMe₃]⁺ ions occurs with splitting off of a NO₂ ^. radical or an XNO₂ molecule (X=H, F, or Cl). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1232–1234, June, 1997.     

Regioselectivity of reactions of vinyl- and isopropenylcyclopentadienide anions with electrophilic agents. Synthesis and crystal structures of complexes [C5H4C(Me)=CH2]ZrCl3 · 2THF and [C5Me4CH=CH2]ZrCl3 · 2THF

Regioselectivity of the reactions of lithium vinyl- and isopropenylcyclopentadienides C₅H₄C(R)=CH₂ ^-Li⁺(R = H, Me) and lithium tetramethylvinylcyclopentadienide C₅Me₄CH=CH₂ ^-Li⁺ with various electrophilic agents (Me₃SiCl, Me₃SnCl, Et₂PCl, 2-chloro-1, 3-dioxaphospholane, and MeI) was studied. Two new monocyclopentadienyl zirconium complexes, [C₅H₄C(Me) = CH₂]ZrCl₃ · 2THF and [C₅Me₄CH=CH₂]ZrCl₃ · 2THF, were synthesized. Their crystal structures were established by X-ray diffraction. The results of quantum chemical calculations for the C₅H₄C(R) = CH₂ ^- (R = H, Me) and C₅Me₄CH=CH₂ ^- anions by the DFT method (RMPW1PW91) with the 6-311+G(d, p) split valence basis set are in good agreement with experimental data on the regioselectivity of their reactions with electrophilic agents.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 390–399, February, 2005.