Perfluoromethyl—element-liganden : XX. Bildung von heteronuclearen zweikernkomplexen des typs mm′(CO)nXY (M = Mn; M′ = Re, Co)

The reactions of MnRe(CO)₁₀ with As₂(CF₃)₄ and MnCo(CO)₉ with P₂(CF₃)₄, As₂(CF₃)₄, S₂(CF₃)₂, Se₂(CF₃)₂, (CF₃)₂EI (E = P, As), (CF₃)₂AsH, (CF₃)₂AsE′CF₃ (E′ = S, Se), (CF₃)₂PSeCF₃, Me₂AsI and (CF₃)₂PPMe₂, respectively, have been studied under various conditions. Besides already known mono- and binuclear compounds the heteronuclear complexes MnRe(CO)₈[As(CF₃)₂]₂ and MnCo(CO)₇[E(CF₃)₂]₂ (E = P, As) are formed. The reactions proceed via cleavage of the M---M′ bond and formation of the mononuclear species Mn(CO)₅X and M′(CO)_nY (M′ = Re, n = 5; M′ = Co, n = 4).     

Perfluormethyl-element-liganden XXVlI [1] Darstellung und spektroskopische untersuchung von W(CO)5L-komplexen (L = R2EER′2, R2EE′R; R,R′ = CH3; CF3; E = P,As; E′ = S,Se, Te)

W(CO)₅L complexes (L = R₂EER′₂, R₂EE′R; R, R′ = CH₃, CF₃; E = P, As; E′ = S, Se, Te) have been prepared by reaction of W(CO)₅·THF with L at room temperature or by redistribution reaction of W(CO)₅E₂Me₄ with E₂(CF₃)₄ or E′₂Me₂ as well as by cleavage of E₂(CF₃)₄ with W(CO)₅EMe₂H. The new compounds were characterized by analytical and spectroscopic (IR, NMR, MS) methods; by comparison with of the data of free and coordinated ligands the effects of complexation are studied.     

Differential cross sections from classical perturbation scattering theory. I. ion—dipole scattering

The formalism for calculating differential cross sections for atom—molecule scattering using classical perturbation scattering theory (CPST) is developed. The results are applied to the scattering of an ion by a dipolar molecule. The interaction potential used in the calculation consists of the ion—dipole and ion—induced dipole terms in the long-range expansion of the potential. Various approximate methods for calculating differential cross sections are also considered.     

Perfluormethyl-Element-Liganden. XXXII. Reaktionen der Metallhydride π-C5H5(CO)3MH (M = Cr,Mo, W) mit Diphosphanen [Ph2−nYnP]2 (Y = I,CN, SiMe3; n = 2, 1, 0)

Perfluoromethyl Element Ligands. XXXII. Reactions of the Metal Hydrides π-C₅H₅(CO)₃MH (M = Cr, Mo, W) with Diphosphanes [Ph_2?nY_nP]₂ (Y = I, CN, SiMe₃; n = 2, 1, 0) The reactions of π-C₅H₅(CO)₃MH (M = Cr, Mo, W) ( 1a – c ) with the symmetric diphosphanes (Ph₂P)₂, [Ph(CN)P]₂, [(CN)₂P]₂, and the cyclophosphane (PPh)₅, respectively, occur under cleavage of the P? P bond. The reactivity decreases in the series The tendency to form binuclear complexes reflects the basicity of the metallated phosphanes π-C₅H₅(CO)₃MPRR′ and increases in the order P(CN)₂ < P(CN)Ph ? P(Ph)H < PPh₂. Iodine containing diphosphanes [Ph(I)P? P(I)Ph and P₂I₄] undergo redox reactions with 1a – c , yielding π-C₅H₅(CO)₃MI and unstable iodo-diphosphanes. No P? P bond cleavage occurs in the reaction of the silyl substituted diphosphanes [Ph(SiMe₃)P]₂ and [(Me₃Si)₂P]₂ with 1a – c , but P? Si bond fission is the preferred reaction giving π-C₅H₅(CO)₃MSiMe₃.     

Reaktive E=C(p‐p)π‐Systeme. 54 [1] Reaktionen des Perfluor‐2‐arsapropens,F3CAs=CF2 (1), mit H‐aciden Verbindungen Me2EH (E = N,P, As) und MeE′H (E′ = O,S, Se)

Reactive E=C(p‐p)π‐Systems. 54 [1] Reactions of perfluoro‐2‐arsapropene, F₃CAs=CF₂ (1), with H‐acidic compounds Me₂EH (E = N, P, As) and MeE′H (E′ = O, S, Se) The reactions of the perfluoro‐2‐arsapropene ( 1 ) with H‐acidic compounds Me₂EH (E = N, P, As) and MeE′H (E′ = O, S, Se), respectively, proceed via addition to the As=C double bond yielding either secondary arsanes F₃C(H)AsCF₂X (X = NMe₂, PMe₂, OMe, SMe) or AsX derivatives (X = AsMe₂, SeMe). Me₂‐AsH is obviously a border case nucleophile because, besides the AsX derivative as main product, small amounts of the arsane are formed indicative for the reverse addition pathway. With the strong base Me₂NH, the addition is followed immediately by HF elimination producing the fairly stable arsaalkene F₃CAs=C(F)NMe₂ ( 4 ) which had already been obtained by reaction of HAs(CF₃)₂ with three equivalents of Me₂NH. The novel rather labile compounds were identified by spectroscopic (NMR, GC/MS) investigations. – Quantum chemical DFT calculations [B3LYP/6‐311+G(d,p)] were carried out to determine the relative energy of the isomeric products and the thermodynamics of the addition reactions.     

Comparative studies of poly(dimethyl siloxanes) using automated GPC-MALDI-TOF MS and on-line GPC-ESI-TOF MS

In this study we compare on-line gel permeation chromatography (GPC) electrospray ionization (ESI) time-of-flight (TOF) mass spectrometry (MS) to automated GPC matrix assisted laser desorption ionization (MALDI) TOF MS for poly (dimethylsiloxane) (PDMS) analysis. Average mass values for a hydroxyl-terminated PDMS (OH-PDMS) sample were obtained and compared to traditional GPC that was calibrated with narrow polystyrene standards, by direct ESI and MALDI MS analysis, by a summation of mass spectra of all GPC fractions, and also by the recalibration method determined by both mass spectrometric methods. Quantitatively, the difference noted here between these hyphenated techniques is that GPC-ESI-TOF MS effectively reports the low-mass oligomers and underestimates the high-mass oligomers, while GPC-MALDI-TOF MS effectively reports the high-mass oligomers and underestimates the low-mass oligomers. In the GPC-ESI-TOF MS experiments, ion current suppression was observed in the high molecular weight region. The suppression effect was confirmed by repeatable sample runs and by injecting different PDMS samples. Higher chromatographic resolution was observed for GPC-ESI-TOF MS compared to GPC-MALDI-TOF MS. In fact, truly mono-disperse oligomers were observed in the low molecular weight range from GPC-ESI MS experiments.     

Darstellung und charakterisierung von verbindungen des typs (CH3)3ME(CF3)2 (M = Si,Ge, Sn; E = P,As)

Various preparative routes for the synthesis of (CH₃)₃SiP(CF₃)₂ are discussed. The most favourable method, reaction of (CH₃)₃MPH₂ with HE(CF₃)₂, provides a good yield of (CH₃)₃ME(CF₃)₂ compounds (M = Si, Ge, Sn; E = P, As). The reaction rate is dependent on M (Si < Ge <Sn) und E (P < As). The stability and reactivity of the (CH₃)₃ME(CF₃)₂ compounds are discussed. The new compounds were characterized by NMR and IR spectra and by cleavage reactions of the M-E bond. ¹H, ¹⁹F NMR and IR spectral data are reported.     

Darstellung und kmr-spektren von (CF3)2ED und CF3ED2 (E = P,As)

(CF₃)₂ED and CF₃ED₂ (E = P,As) may be obtained in high yield by the reaction of (CF₃)₂EI and CF₃EI₂, respectively, with DI/Hg. ¹⁹F- and ³¹P-NMR spectra are reported. When compared with the H-analogues, the deuterated compounds show isotopic shifts of the ¹⁹F- and ³¹P-resonance signals.     

Porous silicon: repeatability of generation?

A systematic investigation of the preparation of porous silicon layers (PSLs) on silicon wafers by anodic treatment in hydrofluoric acid/water/ethanol mixtures under various conditions was carried out with the aim to develop a repeatable process for homogeneous layers. The preparations were controlled by FTIR spectroscopy supported by TOF-SIMS measurements of the uppermost surface area. The repeatability of PLS generation was proved on the grounds of the IR-absorption of SiH_x and O_xSiH_y surface groups with respect to their frequencies and intensities. Uniform properties of PSLs are an essential assumption for defined chemical modifications.