Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen: XIII—Einfluß der Dissoziationsenergie auf intramolekulare aromatische Substitutionen in den Molekül-Ionen von N,N-Dimethyl-N′-phenylformamidinen

The effect of the dissociation energy of the C? X bond (X = H, F, Cl, Br, I) on the formation of benzimidazolium ions (b) by elimination of X from the molecular ions of ortho-substituted N,N-dimethyl-N′-phenylformamidines (I to V) has been investigated. No simple relation is observed between the intensities of ions b and the dissociation energy. Furthermore, the appearance potentials of ions b are not greatly affected by the dissociation energy, although differences of about 2.5 eV are expected for a simple cleavage reaction. The behaviour of the molecular ions of I to V is in accord with a two step addition-dissociation mechanism [M]⁺· → a → b, and the highest activation energy is required in the first addition step. Similar mechanisms are known for aromatic substitution reactions in the condensed phase, but have not been observed for mass spectrometric fragmentations. The detection of additional kinetic energy T in the reaction products by an analysis of the metastable transitions [M]⁺· → b corroborates the proposed mechanism.     

Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen—V: Substituenteneffekte auf Intramolekulare Substitutionen des Phenylrestes in den Massenspektren von N,N-Dimethyl-N′-Phenylformamidinen

The mass spectrum of N,N-dimethyl-N′-phenyl-formamidine (I) contains a large peak due to [M ? H]+-ions. As is shown by deuterium labelling, one of the ortho hydrogen atoms of the phenyl group is lost. The same result has been observed for the corresponding fragmentation of thioformanilide (V). This can be explained by the formation of benzimidazolium-ions (a). The effect of substituents at the phenyl group on the intensities and AP of these ions and on the IP of the molecular ions has been investigated. A mechanism of the cyclization reaction is proposed.     

Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen: XII-Einfluß einer sterischen Hinderung der Mesomerie bei der Fragmentierung von N,N-Dimethyl-N′-4-Biphenylformamidinen

The formation of cyclic [M ? H]⁺ ions (a) in the mass spectra of N,N-dimethyl-N′-arylformamidines is suppressed by electron donating groups in the aryl group para to the formamidine group, due to the participation of resonance structures of type c. This effect is also observed in the mass spectra of N,N-dimethyl-N′-4-biphenylformamidines (III) substituted in the 4′-position. By substitution in the 2-, 2′-, 6- and 6′- positions of III, the formation of resonance structure c′ in the molecular ions is so difficult that these derivatives show the normal fragmentations. This is observed with two methyl groups in the 2- and 2′- positions of III.     

Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen.—I Methoxygruppenwanderungen in den Massenspektren der Methyläther von linearen und verzweigten aliphatischen Polyalkoholen

The formation of 1,1-dimethoxy-alkyl rearrangement ions in the mass spectra of methyl ethers of linear diols, 1,2,3-triols and of derivatives of pentaglycerol and pentaerythritol has been investigated by deuterium labelling and mass measurements. Methoxy group migrations do not occur, or at least only to a small amount, in the mass spectra of the diol-dimethyl ethers. The mass spectra of methyl ethers of 1,2,3-triols exhibit characteristic peaks of the rearrangement ions +CH(OCH₃)₂ and +CR(OCH₃)₂. These ions arise by a 1,3-migration of a methoxy group, probably during a one step degradation of the molecular ion to give a molecule methyl alkenyl ether and a H-atom or alkyl radical as neutral fragments. Large peaks of the rearrangement ion +CH(OCH₃)₂ are observed in the mass spectra of compounds of the following type: A radical ion, formed by loss of HY from the molecular ion, rearranges by methoxy group migration in the mass spectra of these substances. Rearrangement by migration of hydroxy and acetoxy groups are also observed, but no migration of a Cl-atom.     

Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen–II: Methoxygruppenwanderungen und Ringfragmentierungen in den Massenspektren der Methylather cyclischer Polyalkohole

The mass spectra of methyl ethers of cyclopentane-, cyclohexane- and cycloheptanediols contain a characteristic m/e 75 peak of ions of the structure ⊕CH(OCH₃)₂, which are formed by 1,3-, 1,4- or 1,5-migration of a methoxy group. The formation of these ions does not depend on the stereochemistry of the original molecule; probably the methoxy group migration occurs after α-cleavage of the molecular ion in an open chain radical ion: In the case of cycloalkanes with three or more methoxy groups the m/e 75 rearrangement ions give rise to one of the most prominent peaks of the mass spectra. Chemical bonds, terminating at a carbinol-C-atom, are weaker than normal. The presence of several carbinol-C-atoms in the molecular ions of cyclic polymethoxy compounds therefore favours fragmentations which differ from those of simple derivatives of cyclanols and which are typical of the position of the methoxy groups.     

Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen—IXSterische Effekte in den Massenspekten der Stereoisomeren von Decalin-2,3-diolen,Decalin-2,4-Diolen und Ihen Dimethyläthern

The mass spectra of all stereoisomers of decalin-2,3-diol, the corresponding dimethyl ethers and of some deuterated derivatives are discussed. The mass spectra of isomeric decalin-2,3-diols differ only slightly in ion intensities. The mass spectra of the stereoisomeric 2,3-dimethoxy-decalins are nearly identical within the series of transand cisderivatives. A mass spectrometric identification of the stereoisomers of these compounds is therefore diffucult. Stereoselective eliminations from the molecular ion are not observed. The mass spectra -of stereoisomeric decalin-1,4-diols show characteristic differences in the intensities of the[M ? H₂O]⁺˙-ions, which can be related to the geometry of the molecules in a similiar mode as was the case with cyclohexane-1,4-diols, The sterechemical control of the elimination of H₂O from the molecular ions has been confirmed by deuterium labelling. The mass spectra of stereoismeric 1,4-dimethoxy-decalins also differ characteristically in the intensities of the [M ? CH₃OH]⁺˙ ions. Furthermore peak due to the [M ? CH₂O]⁺˙ ions are only observed in the mass spectra of those stereoisomers, which have at least one conformation with a short distance between the two methoxy. The stereospecifity of the CH₃OH- and CH₂O-eliminationjs has also been determined by deuterium labelling.     

Über den Einfluß von Kristallkeimen auf die Bildung von Silicaten der Zusammensetzung 3 CaO · 2 SiO2

On the Influence of Seed Crystals on the Formation of Calcium Silicates with the Composition 3 CaO · 2 SiO₂ The formation of the calcium silicates kilchoanite and rankinite of the composition 3 CaO · 2 SiO₂ is facilitated and enabled, respectively, in the presence of appropriate seed crystals. Kilchoanite (Ca₆[(SiO₄)(Si₃O₁₀)]) is formed from mixtures of CaO and SiO₂ in the autoclave at 200°C and from C? S? H (di, poly) under normal atmosphere at 700°C by seeding for example with kilchoanite, aluminium compounds, γ-Ca₂SiO₄. Rankinite (Ca₃Si₂O₇) can be synthesized under the same conditions, when rankinite itself is applied as seed crystal.     

Über den Einfluß von Substitution auf die Kristallstruktur von SrNi2P2

About the Effect of Substitution on the Crystal Structure of SrNi₂P₂ With several series of mixed crystals the effect of substitution on the crystal structure of SrNi₂P₂ (polymorphic, the structures are variants of the ThCr₂Si₂ type) is investigated by X-ray methods. In the compound Ni completely can be substituted by Co and Cu respectively and also P by As; in Sr_1–xCa_xNi₂P₂ there is a gap of the miscibility between 0.3 ≤ x ≤ 0.6. A low substitution of the several elements more than proportionally changes the structure parameters. In this range the mixed crystals with Ca, Cu, and As, respectively, undergo first order phase transitions with significant changes of the bond distances, which will be interpreted by the results of band structure calculations.     

Mechanismus der Bildung und des Zerfalls von Amidkomplexen,I Kupfer (II) und N,N′-Diglycylpropylendiamin

The kinetics of the formation and dissociation of the copper (II) complex with N, N′-Diglycyl-propylendiamine has been studied. In the formation reaction an intermediate was observed, the structure and reactivity of which is discussed. The rate of dissociation of the complex is proportional to [H⁺]². This is explained by a rapid proton addition to one of the amino groups, followed by the slow reaction of a second proton with the coordinated amide group. The effect of acetate buffer, which increases the dissociation rate, is discussed.     

Massenspektroskopische Fragmentierungsreaktionen. X—Zum Mechanismus der Methyl- und Äthylabspaltung bei benzanellierten 6- und 7-gliedrigen heterocyclen

It is demonstrated that alkyl elimination from 6- and 7-membered benzoheterocyclics usually occurs via several competing mechanisms, the prevalence and nature of which depend upon the heteroatom.     

Mechanismus der Bildung und des Zerfalls von Amidkomplexen,II. Ni2+ und N,N′-Diglycyl-äthylendiamin bzw. N,N′-Diglycyl-1,3-diaminopropan

The kinetics of a two proton transfer between a blue octahedral and a yellow square planar nickel(II) complex with N, N′-diglycylethylenediamine (I, n = 1) resp. N, N′-diglycyl-1, 3-diaminopropane (I, n = 2) have been studied by spectrophotometry and pH-stat technique. The structure of these complexes and the mechanism of their interconversion are discussed and their reactions are compared with the analogous reactions of the copper(II)-N, N′-diglycyl-1, 3-diamino-propane complexes [1].     

Bildung siliciumorganischer Verbindungen. 97. Über den Einfluß der Si-Substituenten (Me,Cl) auf Bildung und Reaktion von Yliden

Formation of Organosilicon Compounds. 97. About the Influence of the Si-Substituents (Me, Cl) upon the Formation and the Reactions of Ylides 1,3-disilapropanes with different grade of chlorination or methylation at the silicon atoms and containing a CCl₂ group cleave the Si? P bond of Me₃SiPMe₂. By subsequent rearrangement ylides with ? PMe₂Cl group are formed. The reactivity of the CCl₂ group depends on the grade of Si-chlorination resp. Si-methylation. Si-methylation decreases the reactivity of the CCl₂ group. The reaction of 1,3-disilapropanes and Me₃SiPMe₂ (molar ratio 1:1) runs in a sequence shown in “Inhaltsübersicht”. Ylid C is able either to react with the initial compound A forming B, or in competition decomposes forming D. Reacting Si-perchlorinated carbosilanes, the decomposition forming D is not to be observed. In Si-methylated ylides like (Me₃Si)₂C?PMe₂? PMe₂ and (Me₃Si)₂C?PMe₂? P(Me)SiMe₃ the ylid carbon atom is able to abstract a proton of the P? CH₃ group resp. P? H groups of the trivalent phosphorus forming (Me₃Si)₂C(H)PMe₂. The rearrangement is proved by deuterated derivatives. The different behaviour is due to the increased basicity of the ylid-C atom in Si-methylated phosphorus ylides. Quite the same behaviour show the phosphorus ylides of 1,3,5-trisilacyclohexane.     

Einfluß der Chelatbildner dppe und dppp auf die Bildung und die Eigenschaften der Pt-Komplexe des tBu2P–P

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XV. Influence of the Chelate Compounds dppe and dppp on Formation and Properties of the Pt Complexes of ^tBu₂P–P The chelating ligands dppe and dppp replace the PPh₃ groups in [η²-{^tBu₂P–P}Pt(PPh₃)₂] 1 yielding [η²-{^tBu₂P–P}Pt(dppe)] 2 and [η²-{^tBu₂P–P}Pt(dppp)] 8 . However, they don't replace the phosphinophosphinidene ligand ^tBu₂P–P. dppm does not react at all with 1 . [η²-{H₂C=CH₂}Pt(dppe)] 3 yields in the presence of ^tBu₂P–P=P(Me)^tBu₂ 4 exclusively Pt(dppe)₂ 5 and elemental Pt; no 2 could be detected. Similarly, [η²-{H₂C=CH₂}Pt(dppp)] 7 reacts with 4 to give mainly Pt(dppp)₂ 9 and Pt; [η²-{tBu₂PP}Pt(PPh₃)₂] 8 is present only as a minor product. [η²-{^tBu₂P–P}Pt(dppe)] 2 crystallizes in the monoclinic space group P2₁/c (no. 14) with a = 1834.40(10) pm, b = 1679.70(10) pm, c = 1125.79(6) pm, β = 103.963(5)°.     

Zum Einfluß der Gasphase auf die thermische Zersetzung von K2[SiF6]

Effect of the Gas Phase on the Thermal Decomposition of K₂[SiF₆] K₂SiF₆ produced in usual ways is contaminated by traces of oxygen and protons. These and traces of water fed by gas atmosphere influence the thermal decomposition reaction. To study the influence of the gas phase definite amounts of H₂O and HF were added. The formation of SiF₄ was determined. The development of a SiO₂ phase in presence of H₂O and other experimental results suggest the construction of a layer on the K₂SiF₆ surface, which hinders further SiF₄ being developped. Temperature and linear velocity of the gas influence the length of a zone of decomposition migrating through the solid. This is explained by sorption and reaction behavior of intermediately formed fluorosiloxanes.     

Zum Einfluß der Substituenten R = Ph,NEt2, iPr und tBu in Triphosphanen, (R2P)2P?SiMe3, und Phosphiden,Li(THF)2[(R2P)2P], auf die Bildung und Eigenschaften von Phosphinophosphiniden-Phosphoranen

Concerning the Influence of the Substituents R = Ph, NEt₂, ⁱPr, and ^tBu in Triphosphanes (R₂P)₂P? SiMe₃ and Phosphides Li(THF)₂[(R₂P)₂P] on the Formation and Properties of Phosphino-phosphinidene-phosphoranes The triphosphanes X₂P? P(SiMe₃)? PY₂ 5, 7, 9, 11, 13 and the derived phosphides Li(THF)₂[X₂P? P? PY₂] 6, 8, 10, 12, 14 were synthesized: 5 and 6 with X₂ = ⁱPr₂ and Y₂ = ^tBu₂, 7 and 8 with X₂ = Y₂ = Ph^tBu, 9 and 10 with X₂ = ^tBu₂ and Y₂ = Ph₂, 11 and 12 with X₂ = Y₂ = Ph₂, and 13 and 14 with X₂ = ^tBu₂ and Y₂ = (NEt₂)₂. The silylated triphosphanes at ?70°C in toluene with CBr₄ may yield X₂P? P?P(Br)Y₂ and X₂P? P(Br)? PY₂, and the lithiated phosphides with MeCl may yield X₂P? P?P(Me)Y₂ and X₂P? P(Me)? PY₂ depending on X and Y. The bromiated product of 5 (X₂ = ⁱPr₂, Y₂ = ^tBu₂) is the ylide ⁱPr₂P? P?P(Br)^tBu₂, and the methylated derivatives of 6 are both ⁱPr₂P? P?P(Me)^tBu₂, ^tBu₂P? P?P(Me)ⁱPr and the methylated triphosphane. Ph₂P? P?P(Br)^tBu₂ as well as the brominated triphosphane are obtained from 9 (X₂ = ^tBu₂, Y₂ = Ph₂), and similarly Ph₂P? P?P(Me)^tBu₂ and the methylated triphosphane from 10 . Compound 14 (X₂ = ^tBu₂, Y₂ = (NEt₂)₂ gives rise to the brominated ylide ^tBu₂)P? P?P(Br) · (NEt₂)₂ and to the brominated triphosphane, and on methylation to ^tBu₂P? P?P(Me)(NEt₂)₂ and to ^tBu₂P? P(Me)? P · (NEt₂)₂ (main product). The Br substituted derivatives decompose already on warming to ?30°C, while the methylated compounds are stable up to 20°C.     

Über den Einfluß der Substituenten im (R3Si)2(P–Si)R2Cl auf Bildung und Eigenschaften der Hexasila-tetraphosphadantane und deren 31P-NMR-Spektren

The Effect of the Substituents in (R₃Si)₂P–SiR₂Cl on the Formation and the Properties of the Hexasilatetraphospha-adamantanes and their ³¹P-NMR Spectra The thermolysis of (Me₃Si)₂P–SiEt₂Cl 4 at 300°C leads to the silylphosphanes with adamantane structure (Et₂Si)_x(Me₂Si)_6–x (x = 0–6), aside of (Me₃Si)₃P, (Et₂MeSi) (Me₃Si)₂P, (Et₂MeSi)₂(Me₃Si)P and Me₃SiCl, Et₂SiCl, Et₂MeSiCl. Due to the different positions of the Et₂Si-bridges in the adamantane cage the compounds featuring x = 2–4, form isomers. The thermolysis of (Me₃Si)₂P–SiEtMeCl 14 occurs analogously and leads to the adamantanes (EtMeSi)_x (Me₂Si)_6–xP₄ (x = 0–6). The introduction of the SiEtMe group causes the existence of chiralic isomers of the compounds featuring x = 2–6. From (Et₃Si)₂P–SiEt₂Cl 24 (Et₂Si)₆P₄ is obtained. The thermolyses of (Me₃Si)₂P–SiPh₂Cl 25 and [(Me₃Si)P–SiPh₂]₂ do not enable the formation of adamantanes with SiPh₂-bridges. They rather lead to Me- and Ph-substituted trisilylphosphanes. The syntheses of the starting compounds 4, 14, 24 , and 25 are reported. The ³¹P-NMR spectra of silylphosphanes with adamantane structure show, that the linear increase of the ³¹P-chemical shift values as dependent on the rising number of Et groups, which is observed in partially Et-substituted methyltrisilylphosphanes, allows the prediction of the δ³¹P values of the specific P atoms in an adamantane cage, heeding both the position and the direction of the SiEt groups in the particular molecule.     

1,2-Diphospha-3,4-diboretane und 1,3-Diphospha-2,4,5-triborolan: Synthese und Struktur sowie Berechnungen zur Molekülstruktur Über den Einfluß von Substituenten auf die Struktur von 1,2-Diphospha-3,4-diboretan

1,2-Diphospha-3,4-diboretanes and 1,3-Diphospha-2,4,5-triborolane: Synthesis and Structure as well as Calculations on the Molecular Structure On the Effect of Substituents on the Structure of 1,2-Diphospha-3,4-diboretane [2 + 2]-Cyclocondensation reactions led to the synthesis of the 1,2-diphospha-3,4-diboretanes [(t-BuP)₂B₂(NMe₂)₂], 1 a , and [(t-BuP)₂B(NMe₂)B(NiPr₂)], 1 b . Their molecular structures have been determined by X-ray methods, and these are compared with the structure of [(t-Bu)P? BN(iPr₂)]₂, 2 a . Compounds 1 show a folded B₂P₂ four membered ring having tert.-butyl groups in anti-positions. Ab initio calculations on 1,2-diphospha-3,4-diboretanes demonstrate that two conformers with anti-orientation of the substituents at the phosphorus atoms can be expected. These differ by the relative orientation of the almost planar P₂BR groups to the BP₂ plane. The influence of substituents (H and NH₂ at the B atoms, and H and Me at the P atoms) on the ring conformation has been studied. Finally, the first derivative of a 1,3-diphospha-2,4,5-triborolane, 3 a , is reported.