Dimethylarsenazid (CH3)2AsN3, Dimethylwismutazid (CH3)2BiN3 und Dimethylthalliumzid (CH3)2TiN3

The reaction of (CH₃)₂AsJ and AgN₃ yields (CH₃)₂AsN₃; a colourless liquid (b. p. 136°C) which dissolves as a monomeric in benzene. (CH₃)₂BiN₃ is precipitated in form of colourless needles (dec. temp. 150°C) from an etherical solution of Bi(CH₃)₃ and HN₃. According to its vibrational and mass spectra the molecules are not associated although the (CH₃)₂BiN₃ is not soluble; dipole association of this polar molecules is assumed for the crystal structure. (CH₃)₂TlN₃ can be obtained from TI(CH₃)₃ and ClN₃ as well as from (CH₃)₂TlOH and HN₃ in form of colourless needles and leaves (dec. temp. 245°C). According to its vibrational spectra it has an ionic structure, (CH₃? Tl? CH₃)⁺N^?₃.     

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.     

Schwingungsspektren und Kraftkonstanten der Übergangsreihen OP(N(CH3)2)3 – OP(CH3)3 und SP(N(CH3)2)3 – SP(CH3)3

Vibrational Spectra and Force Constants of the Series OP(N(CH₃)₂)₃ – OP(CH₃)₃ and SP(N(CH₃)₂)₃ – SP(CH₃)₃ The vibrational spectra (IR and Raman) of the compounds of the title series are recorded and assigned to the normal vibrations. By a simplified force field the valence force constants are calculated and discussed. The results are compared with those of the NMR spectroscopy.     

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.     

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.     

Dative sigma- and pi-bonding in boron-nitrogen compounds: molecular structures of (CH3)2NB(CH3)N(CH3)B(CH3)2 and [(CH3)2B]2NN(CH3)2 determined by gas electron diffraction and quantum chemical calculations

The molecular structures of dimethylamino[(dimethylboryl)methylamino]methylborane, Me2NBMeNMeBMe2 (1) and 1,1-bis(dimethylboryl)-2,2-dimethylhydrazine, (Me2B)2NNMe2 (2) have been determined by gas electron diffraction (GED), density functional theory calculations at the B3PW91/6-311++G** level and ab initio calculations at the MP2/6-311++G** level. 1 adopts an open structure similar to that of the isoelectronic hydrocarbon molecule permethylbutadiene; the central B-N bond distance at 148.0/149.3(7) pm (MP2/GED) corresponds to a single covalent N--B bond distance, the two terminal distances, 140.9/140.5(4) pm and 141.8/141.3(4) pm, correspond to the distance between N and B atoms joined by a covalent sigma-bond and a dative pi-bond. A closed form where the establishment of a dative bond between the terminal N and B atoms has led to the formation of a four-membered ring also corresponds to a minimum on the potential energy surface, but the energy is calculated to be 14.3 kJ mol(-1) higher at the MP2 level. This structure is also incompatible with the GED data. 2 adopts a structure in which a dative sigma-bond between the dimethylamino N atom and one of the boron atoms has led to the formation of a three-membered N(2)B ring. The dative sigma-bond distance is 165.5/164.0(13) pm, the two other bond distances in the ring are N-B=150.6/148.9(9) pm corresponding to a covalent sigma-bond and N-N=145.1/145.4(3) pm. The terminal B--N distance 139.6/138.9(9) pm is consistent with a covalent sigma-bond augmented by a dative pi-bond. An open Y-shaped structure also corresponds to a minimum on the potential energy surface, but the energy is 18.7 kJ mol(-1) higher (MP2) and it is incompatible with the GED data.     

Comparison between CH3(CH2)15SH and CF3(CF2)3(CH2)11SH monolayers on electrodeposited silver

In this paper, two monolayers self-assembled on a silver substrate are compared: a monolayer of n-hexadecanethiol and a monolayer of n-11-perfluorobutylundecanethiol. The protecting properties of both monolayers have been extensively studied by X-ray photoelectron spectroscopy, contact angle, polarization modulation infrared reflection absorption spectroscopy, conventional electrochemical techniques (polarization curves and electrochemical impedance spectroscopy), and scanning vibrating electrode technique. Both monolayers were successfully self-assembled but organization is slightly different, the fluorinated segment introduces small disorganization. Nevertheless, good homogeneous corrosion protection is observed for each monolayer.     

Synthesis and Characterization of （CH3CH2CH2CH2NH3）2SnBr6

1 INTRODUCTION Recently, the researches on inorganic-organic hy-brid compounds represent an advanced field in mate-rial science[1]. At the molecular level, the combina-tion of two extremely different components providesan avenue to design new hybrid materials as well asthe ability to modulate properties of one or more ofthe components[2～6]. Some attractive properties, suchas efficient luminescence[2～4], ideal thermal and me-chanical stability, interesting magnetic[5], non-linearoptical[…     

Schwingungsspektren und Kraftkonstanten von Cl3SiP(CH3)2 und Cl3SiAs(CH3)2

Vibrational Spectra and Force Constants of Cl₃SiP(CH₃)₂ and Cl₃SiAs (CH₃)₂ The i.r. and Raman spectra of Cl₃SiP(CH₃)₂ and Cl₃SiAs (CH₃)₂ have been recorded and assigned. A normal coordinate analysis has been made using a modified valence force field. The SiP force constant is slightly higher than those of alkylsilylphosphines, whereas a similar effect is not found for the SiAs bond.     

Photolysis of CH3C(O)CH3 (248 nm, 266 nm), CH3C(O)C2H5 (248 nm) and CH3C(O)Br (248 nm): pressure dependent quantum yields of CH3 formation

The formation of CH(3) in the 248 or 266 nm photolysis of acetone (CH(3)C(O)CH(3)), 2-butanone (methylethylketone, MEK, CH(3)C(O)C(2)H(5)) and acetyl bromide (CH(3)C(O)Br) was examined using the pulsed photolytic generation of the radical and its detection by transient absorption spectroscopy at 216.4 nm. Experiments were carried out at room temperature (298 +/- 3 K) and at pressures between approximately 5 and 1500 Torr N(2). Quantum yields for CH(3) formation were derived relative to CH(3)I photolysis at the same wavelength in back-to-back experiments. For acetone at 248 nm, the yield of CH(3) was greater than unity at low pressures (1.42 +/- 0.15 extrapolated to zero pressure) confirming that a substantial fraction of the CH(3)CO co-product can dissociate to CH(3) + CO under these conditions. At pressures close to atmospheric the quantum yield approached unity, indicative of almost complete collisional relaxation of the CH(3)CO radical. Measurements of increasing CH(3)CO yield with pressure confirmed this. Contrasting results were obtained at 266 nm, where the yields of CH(3) (and CH(3)CO) were close to unity (0.93 +/- 0.1) and independent of pressure, strongly suggesting that nascent CH(3)CO is insufficiently activated to decompose on the time scales of these experiments at 298 K. In the 248 nm photolysis of CH(3)C(O)Br, CH(3) was observed with a pressure independent quantum yield of 0.92 +/- 0.1 and CH(3)CO remained below the detection limit, suggesting that CH(3)CO generated from CH(3)COBr photolysis at 248 nm is too highly activated to be quenched by collision. Similar to CH(3)C(O)CH(3), the photolysis of CH(3)C(O)C(2)H(5) at 248 nm revealed pressure dependent yields of CH(3), decreasing from 0.45 at zero pressure to 0.19 at pressures greater than 1000 Torr with a concomitant increase in the CH(3)CO yield. As part of this study, the absorption cross section of CH(3) at 216.4 nm (instrumental resolution of 0.5 nm) was measured to be (4.27 +/- 0.2) x 10(-17) cm(2) molecule(-1) and that of C(2)H(5) at 222 nm was (2.5 +/- 0.6) x 10(-18) cm(2) molecule(-1). An absorption spectrum of gas-phase CH(3)C(O)Br (210-305 nm) is also reported for the first time.     

Darstellung und Schwingungsspektren von F3SiAs(CH3)2 und F3SiP(CH3)2

Inhaltsübersicht. Verschiedene Methoden zur Darstellung von F₃SiAs(CH₃)₂ und F₃SiP(CH₃)₂ werden mitgeteilt und diskutiert. Die neuen Trifluorsilylverbindungen werden durch KMR- und IR-Spektren sowie durch Umsetzung mit polaren Reaktanden charakterisiert, Die Schwingungsspektren des F₃SiAs(CH₃)₂ werden mit Hilfe einer Normalkoordinatenanalyse näher untersucht. Preparation and Vibrational Spectra of F₃SiAs (CH₃)₂ and F₃SiP(CH₃)₂ Various preparative routes for the synthesis of F₃SiAs(CH₃)₂ and F₃SiP(CH₃)₂ are discussed. The new trifluoro-silyl compounds are characterized by n.m.r. and i.r. spectra as well as by the reaction with polar compounds. The vibrational spectra of F₃SiAs(CH₃)₂ are investigated using a normal coordinate analysis.     

Threshold photoelectron-photoion coincidence spectroscopy: dissociation dynamics and thermochemistry of Ge(CH3)4, Ge(CH3)3Cl, and Ge(CH3)3Br

Threshold photoelectron-photoion coincidence spectroscopy (TPEPICO) has been used to investigate the gas-phase ionic dissociation energies and thermochemistry of Me4Ge and Me3GeX, (Me = methyl; X = Cl, Br) molecules. The 0 K dissociation onsets for these species have been measured from the breakdown diagram and the ion time-of-flight distributions, which were modeled with the statistical RRKM theory and DFT calculations. The measured 0 K dissociative photoionization onsets were as follows: Me3Ge+ + Me (9.826 +/- 0.010 eV); Me3Ge+ + Cl (10.796 +/- 0.040 eV); Me3Ge+ + Br (10.250 +/- 0.011 eV); Me2GeCl+ + Me (10.402 +/- 0.010 eV); and Me2GeBr+ + Me (10.333 +/- 0.020 eV). These onsets were used to obtain new values for delta(f)H(degrees)298 (in kJ/mol) of the neutral molecules Me3GeCl (-239.8 +/- 5.7) and Me3GeBr (-196.5 +/- 4.3), and also for the following ionic species: Me3Ge+ (682.3 +/- 4.1), Me2GeCl+ (621.1 +/- 5.8), and Me2GeBr+ (657.8 +/- 4.7).     

Interpretation der Schwingungsspektren von (CH3)2SO2, (CH3)2SO(NH) und (CH3)2S(NH)2 unter Verwendung eines Kopplungsstufenverfahrens

Normal Coordinate Analysis of (CH₃)₂SO₂, (CH₃)₂SO(NH), and (CH₃)₂S(NH)₂ using the Method of Stepwise Coupling The qualitative assignment of the vibrational spectra of (CH₃)₂SO₂ ( 1 ), (CH₃)₂SO(NH) ( 2 a ), and (CH₃)₂S(NH)₂ ( 3 a ) and of the C and N deuterated derivatives of 2 a and 3 a is used in a normal coordinate analysis by the method of stepwise coupling. The force constants and the energy distributions are calculated in symmetry coordinates using a generalized valence force field.     

Zur Kenntnis der ionischen Ozonide P(CH3)4O3 und As(CH3)4O3

On the Knowledge of the New Ionic Ozonides P(CH₃)₄O₃ and As(CH₃)₄O₃ P(CH₃)₄O₃ and As(CH₃)₄O₃ were prepared via ion exchange in liquid ammonia and characterized by X-ray-powder, IR, MS and DTA techniques. P(CH₃)₄O₃ and As(CH₃)₄O₃ are isotypic and have a wurtzite-like arrangement of ions with rotationally disordered O₃^?. (Powder data: P6₃mc; P(CH₃)₄O₃: a = 687.8(2), c = 964.6(3) pm; As(CH₃)₄O₃: a = 708.6(1), c = 991.0(3) pm). As(CH₃)₄O₃ shows a displacive phase transition at ?135°C. The low temperature phase is orthorhombic (a = 715.8(7), b = 1 209(1), c = 943.3(1) pm).     

Synthese und Kristallstruktur von Praseodympropionat-trihydrat,Pr(CH3CH2COO)3(H2O)3

Synthesis and Crystal Structure of Praseodymium Propionate Trihydrate, Pr(CH₃CH₂COO)₃(H₂O)₃ Single crystals of Pr(CH₃CH₂COO)₃(H₂O)₃ were obtained by dissolving freshly prepared praseodymium hydroxide in diluted propionic acid. The crystal structure (monoclinic, P2₁/c, Z = 4, a = 1034.2(2) pm, b = 1521.2(3) pm, c = 2086.3(7) pm, β = 102.87(2)°, R1 = 0.0864, wR2 = 0.1196) consists of one-dimensional infinite chains parallel [010]. Pr1 and Pr2 are coordinated by four tridentate-bridging propionate groups. Additionally, Pr1 is coordinated by three “coordination water” molecules, Pr2 by two bidentate propionate groups. There are, in addition, three “crystal water” molecules so that praseodymium propionate trihydrate should be formulated as [(H₂O)₃Pr1(CH₃CH₂COO)₄Pr2(CH₃CH₂COO)₂] (H₂O)₃.     

Zur solvensfreien Darstellung von Tetramethylammoniumsalzen: Synthese und Charakterisierung von [N(CH3)4]2[C2O4], [N(CH3)4][CO3(CH3)], [N(CH3)4][NO2], [N(CH3)4][CO2H] und [N(CH3)4][O2C(CH2)2CO2(CH3)]

Solvent-free Synthesis of Tetramethylammonium Salts: Synthesis and Characterization of [N(CH₃)₄]₂[C₂O₄], [N(CH₃)₄][CO₃CH₃], [N(CH₃)₄][NO₂], [N(CH₃)₄][CO₂H], and [N(CH₃)₄][O₂C(CH₂)₂CO₂CH₃] A general procedure to synthesize tetramethylammonium salts is presented. Several tetramethylammonium salts were prepared in a crystalline state by solvent-free reaction of trimethylamine and different methyl compounds at mild conditions: [N(CH₃)₄]₂[C₂O₄] (cubic; a = 1 114.8(3) pm), [N(CH₃)₄][CO₃CH₃] (P2₁/n; a = 813.64(3), b = 953.36(3), c = 1 131.3(4) pm, β = 90.03(1)°), [N(CH₃)₄][NO₂] (Pmmn; a = 821.2(4), b = 746.5(3), c = 551.5(2) pm), [N(CH₃)₄][CO₂H] (Pmmn; a = 792.8(7), b = 791.7(3), c = 563.3(4) pm) and [N(CH₃)₄][O₂C(CH₂)₂CO₂CH₃] (P2₁; a = 731.1(2), b = 826.4(3), c = 1 025.2(3) pm, β = 110.1(1)°). The tetramethylammonium salts were characterized by IR-spectroscopy and X-ray diffraction. The crystal structures of the methylcarbonate and the nitrite are described.