Massenspektrometrische Untersuchung Organischer Stickstoffverbindungen. XIV—Mechanismus der Piperidin-Eliminierung aus N.N′-(o-Xylylen)-Dipieridin

The electron-impact-induced elimination of piperidine from the title compound could be established by investigation of the unsymmetrically ²H-labelled compound. The mechanism of a 1,1-elimination can be excluded be unequivocally.     

Spektroskopische Bestimmung der Doppelbindungslage in Phospholinen

Zusammenfassung Die Spin-Spin-Kopplungskonstanten der olefinischen Protonen mit dem ³¹P sowie die Feinstruktur der ¹H-NMR-Spektren sind charakteristisch für die Lage der Doppelbindung. Vielfach kann auch die Intensität der _C=C-Schwingung im IR zur Bestimmung der Doppelbindungslage benutzt werden. Massenspektren geben nur in Ausnahmefällen Hinweise, können jedoch zur exakten Bestimmung des Molekulargewichts dienen.

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Summary The spin-spin coupling constants of the olefinic protons with the phosphorus-31 as well as the fine structure of the nmr-spectra are characteristic for the position of the double bond. In the infrared, the intensity of the _C=C-frequency may often serve as indication of the position of the double bond. The applicability of mass spectra is limited to a small number of compounds. They may be used, however, for an accurate determination of the molecular weight.

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Die Ausführung der Untersuchungen erfolgte unter Mitarbeit von Herrn F. Dlugosch, Herrn H. Au und Fräulein R. Barth.

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Herrn Dr. C. A. Reilly, Shell-Development Company, Emeryville, USA, danken wir für die Überlassung getesteter Programmkartensätze zur Berechnung der NMR-Spektren.     

Alkoholyse von Tris(dimethylamino)-arsin

Alcoholysis of Tris (dimethylamino)arsine The reaction of tris(dimethylamino)arsine with alcoholes and thioles leads to the formation of esters of the general formula As(XR)₃ (X = O and S). The reaction is a suitable preparative method for the synthesis of the esters As(XR)₃ (X = O and S). By alcoholysis in steps results an equilibrium system containing the molecules AsX₃, AsX₂Y, AsXY₂, and AsY₃ (X = OR, Y = N(CH₃)₂).     

Synthese der Stannatetraphospholane (tBuP)4SnR2 (R = tBu,nBu, C6H5) und (tBuP)4Sn(Cl)nBu Molekül- und Kristallstruktur von (tBuP)4Sn(tBu)2

Synthesis of the Stannatetraphospholanes (tBuP)₄SnR₂ (R = tBu, nBu, C₆H₅) and (tBuP)₄Sn(Cl)nBu Molecular and Crystal Structure of (tBuP)₄Sn(tBu)₂ The reaction of the diphosphide K₂[tBuP-(tBuP)₂-PtBu] 4 with the halogenostannanes (tBu)₂SnCl₂, (nBu)₂SnCl₂, (C₆H₅)₂SnCl₂ or nBuSnCl₃ in a molar ratio of 1 : 1 leads via a [4 + 1]-cyclocondensation reaction to the stannatetraphospholanes (tBuP)₄SnR₂ 3 b–3 d and (tBuP)₄Sn(Cl)nBu 3 e , respectively, with the binary 5-membered P₄Sn ring system. 3 b was characterized by a single crystal structure analysis; the 5-membered ring exists in a planar conformation. The compounds 3 b–3 e were identified by NMR and also by mass spectroscopy; the ³¹P{¹H}-NMR spectra of 3 b–3 d showed an AA′MM′ (AA′MM′X), 3 e on the other hand an ABCD (ABCDX) spin system.     

Die gravimetrische Phosphorbestimmung in wolframhaltigen St?hlen

Zusammenfassung Einige der üblichen Methoden zur Phosphorbestimmung in wolframlegierten Stählen werden unter Anwendung von ¹⁸⁵W und ³²P einer Nachprüfung unterzogen. Dabei erweisen sich die Phosphorverluste durch Adsorption an dem Wolframsäureniederschlag als gering, so daß sie bei weniger anspruchsvollen Bestimmungen unberücksichtigt bleiben können. Erheblich größer sind dagegen die Fehler, die durch Mitfällung von Wolframsäure mit dem Ammoniummolybdatophosphatniederschlag entstehen können. Es werden zwei Methoden angegeben, nach denen eine quantitative Abtrennung des Wolframs und damit eine sichere Bestimmung des Phosphors möglich ist.Herr Prof. Dr.-Ing. K. Schwabe ermöglichte es uns freundlicherweise, die Untersuchungen mit radioaktivem Wolfram und Phosphor im Zentralinstitut für Kernphysik Rossendorf, Bereich Radiochemie, durchzuführen. Ihm sei auch an dieser Stelle herzlichst gedankt.     

A mass spectrometry study of XCO+, X=Si, Ge: is SiCO+ a main group carbonyl? Comments on the bonding in ground state SiCO and the

The cation [Si,C,O]+ has been generated by 1) the electron ionisation (EI) of tetramethoxysilane and 2) chemical ionisation (CI) of a mixture of silane and carbon monoxide. Collisional activation (CA) experiments performed for mass-selected [Si,C,O]+, generated by using both methods, indicate that the structure is not inserted OSiC+; however, a definitive structural assignment as Si(+)-CO, Si(+)-OC or some cyclic variant is impossible based on these results alone. Neutralisation-reionisation (+NR+) experiments for EI-generated [Si,C,O]+ reveal a small peak corresponding to SiC+, but no detectable SiO+ signal, and thus establishes the existence of the Si(+)-CO isomer. CCSD(T)@B3LYP calculations employing a triple-zeta basis set have been used to explore the doublet and quartet potential-energy surfaces of the cation, as well as some important neutral states. The results suggest that both Si(+)-CO and Si(+)-OC isomers are feasible; however, the global minimum is 2 pi SiCO+. Isomeric 2 pi SiOC+ is 12.1 kcal mol-1 less stable than 2 pi SiCO+, and all quartet isomers are much higher in energy. The corresponding neutrals Si-CO and Si-OC are also feasible, but the lowest energy Si-OC isomer (3A") is bound by only 1.5 kcal mol-1. We attribute most, if not all, of the recovery signal in the +NR+ experiment to SiCO+ survivor ions. The nature of the bonding in the lowest energy isomers of Si(+)-(CO,OC) is interpreted with the aid of natural bond order analyses, and the ground state bonding of SiCO+ is discussed in relation to classical analogues such as metal carbonyls and ketenes.     

Aggregation of PMe3-stabilized molybdenum sulfides and the catalytic dehydrogenation of H2S

The reactivity of [MoS(4)](2-) (1) toward PMe(3) was explored in the presence and absence of proton donors. Whereas MeCN solutions of (Et(4)N)(2)[MoS(4)] and PMe(3) are stable, in the presence of H(2)S such solutions catalyze formation of H(2) and SPMe(3). Addition of NH(4+) to such solutions afforded MoS(2)(PMe(3))(4) (2), which can be prepared directly from (NH(4))(2)[1]. Compound 2 is reactive toward thiols via a process proposed to involve the initial dissociation of one PMe(3) ligand, a hypothesis supported by the relative inertness of trans-MoS(2)(dmpe)(2). Benzene solutions of 2 react with EtSH to give Mo(2)(mu-S)(mu-SH)(PMe(3))(4)(SEt)(3) (3Et). Analogous reactions with thiocresol (MeC(6)H(4)SH) and H(2)S gave Mo(2)(mu-S)(mu-SH)(PMe(3))(4)(SR)(3) (R = tol, H). Crystallographic analyses of 3Et, 3H, and 3tol indicate dinuclear species with seven terminal ligands and a Mo(2)(mu-SR)(mu-S) core (r(Mo)(-)(Mo) = 2.748(1) A). From reaction mixtures leading to 3Et from 2, we obtained the intermediate Mo(IV)(2)(mu-S)(2)(SEt)(4)(PMe(3))(2) (4), an edge-shared bis(trigonal pyramidal) structure. Compounds 3H and 3Et react further with H(2)S to give Mo(4)(mu(2)-S)(4)(mu(3)-S)(2)(PMe(3))(6)(SH)(2) (5H) and Mo(4)(mu(2)-S)(4)(mu(3)-S)(2)(PMe(3))(6)(SEt)(2) (5Et), respectively. Analogously, W(4)(mu(2)-S)(4)(mu(3)-S)(2)(PMe(3))(6)(SH)(2) was synthesized from a methanol solution of (NH(4))(2)WS(4) with H(2)S and PMe(3). A highly accurate crystallographic analysis of (NH(4))(2)MoS(4) (R(1) = 0.0193) indicates several weak NH.S interactions.     

Durch Nachbargruppenbeteiligung induzierte (1,2)-Chlorwasserstoff-Eliminierung aus ionisiertem 2-(β-Chloräthyl)- benzoesäuremethylester

By using deuterium labelled compounds and collisional activation spectra the mechanism of the unusually intensive HCl elimination from 2-(β-chloroalkyl)benzoic acid methyl ester as well as the structure of the product ion have been elucidated. It can be shown that the structure of the stable ion (lifetime τ～10?5 s) is best represented by 2-vinyl benzoic acid methyl ester whereas the reactive ion (lifetime τ<10^?6 s) at least partially rearranges to a cyclic ion. The hydrogen chloride elimination from 2-(β-chloroalkyl)benzoic acid is apparently a simple 1,2 process. A closer examination reveals that the reaction represents a further example of an unusual neighbouring group participation of the ester function.