Thermochemistry and dissociative photoionization of Si(CH3)4, BrSi(CH3)3, ISi(CH3)3, and Si2(CH3)6 studied by threshold photoelectron-photoion coincidence spectroscopy

Threshold photoelectron-photoion coincidence spectroscopy (TPEPICO) has been used to study the dissociation kinetics and thermochemistry of Me(4)Si, Me(6)Si(2), and Me(3)SiX, (X = Br, I) molecules. Accurate 0 K dissociative photoionization onsets for these species have been measured from the breakdown diagram and the ion time-of-flight distribution, both of them analyzed and simulated in terms of the statistical RRKM theory and DFT calculations. The average enthalpy of formation of trimethylsilyl ion, Delta fH(o)298K(Me(3)Si(+)) = 617.3 +/- 2.3 kJ/mol, has been determined from the measured onsets for methyl loss (10.243 +/- 0.010 eV) from Me(4)Si, and Br and I loss from Me(3)SiBr (10.624 +/- 0.010 eV) and Me(3)SiI (9.773 +/- 0.015 eV), respectively. The methyl loss onsets for the trimethyl halo silanes lead to Delta fH(o)298K(Me(2)SiBr(+)) = 590.3 +/- 4.4 kJ/mol and Delta fH(o)298K(Me(5)Si(2)(+)) = 487.6 +/- 6.2 kJ/mol. The dissociative photoionization of Me(3)SiSiMe(3) proceeds by a very slow Si-Si bond breaking step, whose rate constants were measured as a function of the ion internal energy. Extrapolation of this rate constant to the dissociation limit leads to the 0 K dissociation onset (9.670 +/- 0.030 eV). This onset, along with the previously determined trimethylsilyl ion energy, leads to an enthalpy of formation of the trimethylsilyl radical, Delta fH(o)298K(Me(3)Si(*)) = 14.0 +/- 6.6 kJ/mol. In combination with other experimental values, we propose a more accurate average value for Delta fH(o)298K(Me(3)Si(*)) of 14.8 +/- 2.0 kJ/mol. Finally, the bond dissociation enthalpies (DeltaH(298K)) Si-H, Si-C, Si-X (X=Cl, Br, I) and Si-Si are derived and discussed in this study.     

Bildung und Eigenschaften von Li2P7R (R = Si(CH3)3, CH3, C(CH3)3)

Formation and Properties of Li₂P₇R (R = Si(CH₃)₃, CH₃, C(CH₃)₃) The reaction of P₇(Sime₃)₃ with Li₃P₇ in the molar ratio of 2:1 yields LiP₇(Sime₃)₂, and in the molar ratio of 1:2 Li₂P₇Sime₃ is formed. Li₂P₇me and Li₂P₇Cme₃ (me = CH₃) are obtained by reaction of white phosphorus with Lime, or LiCme₃, respectively [2]. The compounds Li₂P₇R (R = Sime₃, Cme₃, me) show typical valence tautomerism, as established by ³¹P-n.m.r. spectroscopy at various temperatures. Also LiP(Sime₃)₂ transforms P₇(Sime₃)₃ to yield Li₂P₇Sime₃ but in this reaction considerable cleavage of P? P bonds occurs, too.     

Die Kristallstruktur von [InI · C6D6][{(CH3)3Si}3C‐InI3]; ein Nebenprodukt der Umsetzung von InI3 mit basefreiem Li‐C(Si(CH3)3)3

The title compound is formed together with Li[Tsi‐InI₃] (the main product), (Tsi‐In(Me)I)₂ and (Tsi)₂InMe in very low yield in the reaction of InI₃ with Tsi‐Li (Tsi = ‐C(Si(CH₃)₃)₃)in toluene. According to the X‐ray structure determination this compound crystallizes in the triclinic space group P&1marc; and consists of slightly associated dimers of [Tsi‐InI₃]^‐ anions via weak In^I···I(‐In^III) contact‐bonds of 345.6(1) to 373.8(2) pm. Additionally the In^I atom is capped by a D₆‐benzene molecule.     

Mass spectra of polymeric thioformaldehydes (CH2S)3, (CH2S)4, (CH2S)5 and (CH2S)x

The mass spectral fragmentations of various thioformaldehydes, 1,3,5-trithiacyclohexane, 1,3,5,7-tetrathiacyclooctane, 1,3,5,7,9-pentathiacyclodecane and a polymeric form (CH₂S)_x have been examined. The principal features of the spectra are reported. The fragmentation occurred by fracture of the ring in the cyclic compounds with or without rearrangement.     

Schwingungsspektrum und Kraftkonstanten des Tetrakis-trimethylsilyl-hydrazin,[(CH3)3Si]2N-N[Si(CH3)3]2

The vibrational spectra (IR and RAMAN ) have been taken for tetrakis-trimethylsilyl-hydrazine. A complete assignment of all observed bands is given. The silicium-nitrogen vibrations are interpreted in terms of a D_2d configuration. Force constants of the GVFF are computed. The valency force constant of the nitrogen-nitrogen bond is comparable to that of N₂H. This proves the interaction of the silicium atoms with the free electron pairs of the two nitrogen atoms.     

Tris(tris(trimethylsilyl)silyl)gallium,Ga{Si(Si(CH3)3)3}3

The title compound has been prepared in good yield by the reaction of gallium trichloride with base‐free hypersilyl lithium (Li–Si(SiMe₃)₃, Me = CH₃) in a 1 : 3 molar ratio. Ga(Si(SiMe₃)₃)₃ is monomeric in solution and in the solid state. The compound has been characterized with NMR, IR and Raman techniques as well as by an X‐ray structure determination (planar GaSi₃‐skeleton, monoclinic space group P2₁/c, Z = 4, d(Ga–Si) = 249,8 ± 0,2 pm).     

Aryl- und Arin-Komplexe von Übergangsmetallen der sechsten Gruppe Darstellung von [Mo(p-C6H4CH3)6(Li · OC4H10)3] und [W(p-C6H4CH3)4(C6H3CH3)2(Li · OC4H10)4] sowie NMR-spektroskopische Untersuchung des W-Komplexes

Aryl and Aryne Complexes of Group Six Transition Metals. Preparation of [Mo(p-C₆H₄CH₃)₆(Li · OC₄H₁₀)₃] und [W(p-C₆H₄CH₃)₄(C₆H₃CH₃)₂(Li · OC₄H₁₀)₄] and NMR Spectroscopic Investigation of the W Complex Molybdenum(V) chloride reacts with an etheral solution of p-tolyllithium (molar ratio 1:10) to yield a yellow, strongly paramagnetic hexatolylo complex ([MoTol₆(Li · S)₃]¹) (μ_eff = 3.51 B.M.), while from tungsten(V) bromide and p-tolyllithium (molar ratio 1:11) a blackish violet, diamagnetic complex [WTol₄Tn₂(Li · S)₄] is formed, containing two tolylene or tolyne groups for ligands. The ¹H-NMR spectrum points to the Tol-ligands being influenced by the methyl groups of the Tn-ligands.     

NaMn6(P2O7)2(P3O10) and KCd6(P2O7)2(P3O10)

The crystal structures of two new diphosphates, sodium hexamanganese bis­(diphosphate) triphosphate, NaMn₆(P₂O₇)₂(P₃O₁₀), and potassium hexacadmium bis­(diphosphate) triphosphate, KCd₆(P₂O₇)₂(P₃O₁₀), confirm the rigidity of the M₆(P₂O₇)₂(P₃O₁₀) matrix (M is Mn or Cd) and the relatively fixed dimensions of the tunnels extending in the a direction of the unit cell. The compounds are isomorphous; the P₂O₇^4? anion and the alkali metal cations lie on mirror planes. Bond‐valence analysis of the bonding details of the atoms found within the tunnels permits a prediction of the conductivity.     

Über die Darstellung der Dimercapto(methyl)sulfonium-Salze[CH3S(SH)2]+AsF−6 und [CH3S(SH)2]+SbCl−6 und der Bis(chlorthio)Methylsulfonium-Salze [CH3S(SCI)2]+ AsF6−und [CH3S(SCL)2]+SbCl−6

On the Preparation of Dimercapto(methyl)Sulfonium Salts [CH₃S(SH)₂]⁺ AsF₆^? and [CH₃S(SH)₂]⁺SbCl₆^? and the Bis(chlorothio)methylsulfonium Salts [CH₃S(SCI)₂]⁺ AsF₆^? and [CH₃S(SCI)₂]⁺ SbCl₆^? The preparation of the dimercapto(methyl)sulfonium salts [CH₃S(SH)₂]⁺ AsF₆^? and [CH₃S(SH)₂]⁺SbCl₆^? from [CH₃SCl₂]⁺ salts and H₂S at 195 K is reported. The salts are stable below 210 K. They are characterized by additional Raman spektroscopic measurements of the isotopic labelled cations [CH₃S(SD)₂]⁺, [CH₃S(³⁴SH)₂]⁺ and [CH₃S(₃₄SD)₂]⁺. The dimercapto(methyl)sulfonium salts are transfered into bis(chlorthio)methylsulfonium salts by reaction with Cl₂ at 195 K.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.     

精确控制合成Au36(SR)24金原子簇(SR = SPh,SC6H4CH3, SCH(CH3)Ph,SC10H7)

近十几年来,具有原子精确的金原子簇(Au_nL_m)逐渐发展成一种新型可靠的金纳米材料。在本研究中,报道一种简单实用合成脂肪或者芳香巯基保护Au₃₆(SR)₂₄金原子簇的方法。通过“尺寸聚焦”方法,成功地获得Au₃₆(SCH(CH₃)Ph)₂₄,Au₃₆(SC₆H₄CH₃)₂₄,Au₃₆(SPh)₂₄及Au₃₆(SC₁₀H₇)₂₄等金原子簇。这些原子簇通过UV-Vis光谱,电喷雾(ESI)和基质辅助激光解析飞行时间(MALDI)质谱以及TGA等表征进行了进一步的确定。同时发现在UV-Vis光谱中,芳香巯基保护Au₃₆(SR)₂₄金原子簇发生了明显的红移现象;例如与Au₃₆(SCH(CH₃)Ph)₂₄原子簇相比,萘巯基保护的Au₃₆(SC₁₀H₇)₂₄原子簇在570 nm左右的吸收峰发生了13 nm的位移。     

A Tri-Coordinate-Magnesium Silylamide Complex: {[(CH3)3Si]2N}2MgO(CH2CH2)2OMg{N[Si(CH3)3]2}2

The reaction of diethylmagnesium dioxane adduct solution with 1,1,1,3,3,3-hexamethyldisilazan ((CH₃)₃SiNHSi(CH₃)₃) gives {[(CH₃)₃Si]₂N}₂MgO(CH₂CH₂)₂OMg{N[Si(CH₃)₃]₂}₂ (1); this alkoxomagnesium silylamide in the solid state contains unprecedented three-coordinate magnesium and oxygen atoms.     

[{(CH3)3Si}3C–Li–C{Si(CH3)3}3][Li · 3(OC4H8)] und {(CH3)3Si}3C–Li · O=C(Si(CH3)3)2, zwei neue Addukte des Lithium‐trisylmethanids

[{(CH₃)₃Si}₃C–Li–C{Si(CH₃)₃}₃][Li · 3(OC₄H₈)] and {(CH₃)₃Si}₃C–Li · O=C(Si(CH₃)₃)₂, two New Adducts of Lithium Trisylmethanide Sublimation of (Tsi–Li) · 2 THF (Tsi = –C(Si(CH₃)₃)₃) at 180 °C and 10^–4 hPa gives (Tsi–Li) · 1.5 THF in very low yield. The X‐ray structure determination shows an almost linear [Tsi–Li–Tsi]^– anion connected by short agostic Li…C contacts with the threefold THF‐coordinated Li‐cation. Base‐free Tsi–Li, solved in toluene is decomposed by oxygen, forming the strawberry‐colored ketone O=C(SiMe₃)₂, which forms an 1 : 1 adduct with undecomposed Tsi–Li. The X‐ray structure elucidation of this compound is also discussed.     

Diskussion Intramolekularer Wechselwirkungen an RC6H4(CH3)2SiF-, RC6H4(CH3)2SiOCH3-, RC6H4O(CH3)2SiF-, RC6H4OSi(CH3)3- und (CH3)3MF- [M  C,Si, Ge,Sn] Verbindungen

Chalcogenide Glasses with Organic Components. I. Glasses of the Selenium-Arsenic-Bromine-Azobenzene System New glasses were prepared by melting suitable glasses of the system Se? As? Br and of Bis(selenenylbromido)-azobenzene, and cooling them subsequently. Azobenzene groups are connected with the inorganic glass by selenium-carbon bonds. These substances represent the link between polymers as part of the organic chemistry and inorganic glasses. The structures of these products are discussed on the basis of thermal, conductivity, and infrared spectroscopic studies and of density measurements.