Thermischer Zerfall von AlPO4−SiO2-Mischkristallen

Zusammenfassung AlPO₄-10 Mol% SiO₂-Mischkristalle mit stapelfehlgeordneter Cristobalit-Tridymit-Struktur zeigen gegenüber reinem AlPO₄ mit Cristobalit-Struktur eine auffällige Hemmung der thermischen Zersetzung. Dies wird auf die Bildung thermisch stabiler diffusionshemmender SiO₂–P₂O₅-Schmelzhäute zurückgeführt. Zusätze von GeO₂, SnO₂ oder TiO₂ zu AlPO₄ bewirken diesen Hemmungseffekt nicht. Schmelzen von GeP₂O₇, SnP₂O₇ und TiP₂O₇ zerfallen bei 1400°C schnell. Mechanische Gemenge von AlPO₄ und SiO₂ zeigen den Hemmungseffekt nur schwach. AlAsO₄ zerfällt mit und ohne SiO₂-Zusatz rasch oberhalb 1000°C.

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Thermal decomposition of AlPO₄–SiO₂ mixed crystals

AlPO₄-10 mole% SiO₂ solid solutions, representing the stacking-disordered cristobalite-tridymite structure, in contrast to pure AlPO₄ show a remarkable reduction of rate of thermal decomposition. This is brought into connection with the formation of molten surface layers of SiO₂–P₂O₅. Simple mixtures of AlPO₄ with SiO₂ in the form of quartz powder or amorphous silica gel show this effect only scarcely. Additions of GeO₂, SnO₂ or TiO₂ do not show this effect at all. In contrast to melts of the composition SiP₂O₇, melts of GeP₂O₇, SnP₂O₇ and TiP₂O₇ decompose quickly at 1400°C. AlAsO₄ even with the addition of SiO₂ decomposes very rapidly above 1000°C.

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Mit 5 Abbildungen

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Thermischer Zerfall einfacher und komplexer Cyanide unter Bildung von Alkalimetallen,besonders von Kalium

Ohne Zusammenfassung     

Über die GeO2-Modifikationen (Zerfall des Ammonium-hydrogengermanates)

Ohne ZusammenfassungMit 1 Abbildung     

Zerfall der Dimeren des Acenaphtylens als Folge der Alkalimetall-Reduktion

Trans- and cis-dinaphthylene-cyclobutane formed by photodimerisation of acenaphthylene are shown to produce the radical anions of the monomer on sodium reduction. This is explained in terms of the large energy difference between the lowest antibonding MOs of the dimers and of the monomer.     

Metallkomplexe des Hexamethyl-trisila-tetraphospha-nortricyclen P4 (Sime2)3

Transition Metal Complexes of the Hexamethyl-trisila-tetraphospha-nortricyclene P₄ (Sime ₂) ₃ P₄(Sime₂)₃ 1 reacts with Mo(CO)₆, Cr(CO)₅THF, and Mn(η-C₅H₅)(CO)₂THF to give crystalline complexes in which 1 functions as a monodentate ligand. In each compound one phophorus atom of the cyclotriphosphane ring coordinates to the metal atom. Using Mn(η-C₅H₅)(CO)₂THF, two different P atoms of the P₃ Cr(CO)₄ norbornadiene and 1 react, yielding the dimeric, red, crystalline compound (CO) ₄Cr[μ-P₄(Sime₂)₃]₂Cr(CO)₄. In this complex the two molecules of 1 are both bonded by two P atoms of the P ₃ ring to the two Cr(CO)₄ Units, forming a six-memered (CrP₂)₂ring.     

Der thermische Zerfall des tBu2P?PP(Me)tBu2

The Thermal Decomposition of ^tBu₂P? P?P(Me)^tBu₂ The thermal decomposition of ^tBu₂P? P?P(Me)^tBu₂ 2 in C₆H₆ at 20°C is detectable after 10 h; ^tBu₂PMe, (^tBu₂P)₂PH and small amounts of the cyclotetraphosphanes P₄(P^tBu₂)₄ and P₄(P^tBu₂)₂ are formed. At 70°C (14 h) 83% of 2 are decomposed, and even 96% after 74 h. The main products are ^tBu₂PMe (68%) and P₄(P^tBu₂)₄ (20%). With 2,3-dimethyl-1,3-butadiene as a trapping reagent ^tBu₂PMe (62%) is still the main product, however, P₄(P^tBu₂)₄ is no longer found, but 1,2-bis(di-tert-butylphosphino)-4,5-dimethyl-1,2-diphosphacyclohexene-4 (22%) is formed instead. Also with cyclohexene ^tBu₂PMe (78%) remains the major product besides P₄(P^tBu₂)₄ (9%) and small amounts of the trapping product 7-di-tert-butylphosphino-7-phosphabicyclo[4.1.0]heptane. Thus, the thermal decomposition of 2 at 70°C proceeds very similar to that of ^tBu₂P? P?P(Br)^tBu₂ at ?30°C and starts yielding and the phosphinophosphinidene ^tBu₂P? P. In CH₂Cl₂ the decomposition of 2 includes the chlorination of the ylidic molecule.     

Die Kristallstruktur des Dodekamethyl-hexasila-tetraphospha-adamantans (Sime2)6P4

Crystal Structure of Dodecamethyl-hexasila-tetraphospha-adamantane (Sime₂)₆P₄ Dodecamethyl-hexasila-tetraphospha-adamantane (Sime₂)₆P₄ crystallizes in the cubic space group I 4 3m with a = 1081.7 pm and Z = 2 formula units. The bond lengths are P? Si = 224.9 pm, C? Si = 186.4 pm and C? H = 87 pm. The bond angles at the P-atoms are 104.4° and at the Si-atoms 118.8°. – The structure of the isotypic compound (Geme₂)₆P₄ was refined.     

Alkylierung in der 2-Stellung von (2S, 4R)- 4-Hydroxyprolin unter Retention

Alkylation in the 2-Position of (2S, 4R)-4-Hydroxyproline with Retention of Configuration O-Acetyl-4-hydroxyproline ( 1b ) is condensed with pivalaldehyde to give a single stereoisomer of the 2-(tert-butyl)-4-oxo-3-oxa-1-azabicyclo[3.3.0]oct-7-yl acetate ( 3 ). This is converted to the enolates 4 or 5 , reactions of which with alkyl halides, aldehydes, and acetone (→ 6,9,10,11 ) are diastereoselective (lk-1,3-induction). Cleavage of the corresponding products furnishes the enantiomerically pure 2-deuterio-, 2-methyl-, 2-allyl-, and 2-benzyl-substituted 4-hydroxyprolines 2a–2d .     

Bildung und struktur der Cyclophosphane P4(CMe3)2[P(CMe3)2]2 und P4(SiMe3)2[P(CMe3)2]2

Formation and Structure of the Cyclophosphanes P₄(CMe₃)₂[P(CMe₃)₂]₂ and P₄(SiMe₃)₂[P(CMe₃)₂]₂ n-Triphosphanes showing a SiMe₃ and a Cl substituent at the atoms P¹ and P², like (Me₃C)₂P? P(SiMe₃)? P(CMe₃)Cl 3 or (Me₃C)₂P? P(Cl)? P(SiMe₃)₂ 4 are stable only at temperatures below ?30°C. Above this temperature these compounds lose Me₃SiCl, thus forming cyclotetraphosphanes, P₄(CMe₃)₂[P(CMe₃)₂]₂ 1 out of 3 , P₄(SiMe₃)₂[P(SiMe₃)₂]₂ 2a (cis) and 2b (trans) out of 4 . The formation of 1 proceeds via (Me₃C)₂P? P?PCMe₃ 5 as intermediate compound, which after addition to cyclopentadiene to give the Diels-Alder-adduct 6 (exo and endo isomers) was isolated. 6 generates 5 , which then forms the dimer compound 1 . Likewise (Me₃C)₂P? P?P-SiMe₃ 8 (as proven by the adduct 7 ) is formed out of 4 , leading to 2a (cis) and 2b (trans). Compound 1 is also formed out of the iso-tetraphosphane P[P(CMe₃)₂]₂[P(CMe₃)Cl] 9 , which loses P(CMe₃)₂Cl when warmed to a temperature of 20°C. 1 crystallizes monoclinically in the space group P2₁/a (no. 14); a = 1762.0(15) pm; b = 1687.2(18) pm; c = 1170.5(9) pm; β = 109.18(5)° and Z = 4 formula units in the elementary cell. The molecule possesses E conformation. The central four-membered ring is puckered (approx. symmetry 4 2m; dihedral angle 47.4°), thus bringing the substituents into a quasi equatorial position and the nonbonding electron pairs into a quasi axial position. The bond lengths in the four-membered ring of 1 (d (P? P) = 222.9 pm) are only slightly longer than the exocyclic bonds (221.8 pm). The endocyclic bond angles \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \beta $\end{document}(P/P/P) are 85.0°, the torsion angles are ±33° and d (P? C) = 189.7 pm.     

Eine neue Version der Epoxyketon → Alkinon-Fragmentierung: Thermischer Zerfall der Hydrazone aus α,β-Epoxycarbonyl-verbindungen und N-Amino-aziridinen. Vorläufige Mitteilung

A new version of the epoxyketone → alkynone fragmentation is described. Hydrazones derived from cyclic α,β-epoxy-ketones and N-amino-aziridines decompose thermally into molecular nitrogen, an olefinic fragment and an acetylenic carbonyl compound (compare scheme 1). The reaction of phenylglyoxal with N-amino-phenyl-aziridine at room temperature produces styrene and diazo-acetophenone in high yield (compare scheme 3).     

Untersuchungen zur Metallierung der Cyclophosphane P4(Cme3)3(Sime3), P4(Cme3)2(Sime3)2, P4(Sime3)4

Investigations Concerning the Metallation of the Cyclotetraphosphanes P₄(Cme₃)₃(Sime₃), P₄(Cme₃)₂(Sime₃)₂, and P₄(Sime₃)₄ The reaction of white phosphorus with LiCme₃ and me₃SiCl yields P₄(Sime₃)(Cme₃)₃ 1 . With n-buLi this crystalline cyclotetraphosphane forms the crystalline LiP₄(Cme₃)₃. In the same manner, n-buLi, with trans-P₄(Sime₃)₂(Cme₃)₂ 2 to yields LiP₄(Sime₃)(Cme₃)₂, which in contrast to LiP₄(Cme₃)₃ decomposes within a few hours yielding P(Sime₃)₂n-bu 6 , P(Sime₃)₃ 8 , LiP(Sime₃)₂ 9 and also the cyclic compounds P₄(Sime₃)(Cme₃)₃ 10 , LiP₄(Cme₃)₃ 11 and LiP₃(Cme₃)₂ 12 . The composition of the product mixture depends on the molar ratio of 2 to LiC₄H₉. At a molar ratio of 1:1 11 and 12 are not jet observed. At molar ratios of 1:1.5 and 1:2 P(Sime₃)₃ is not found. The amount of 11 and 12 grows with increasing concentration of n-buLi. On addition of n-buLi the solution of P₄(Sime₃)₄ immediately turns red. Li₃P₇ and Li₂P₇(Sime₃) (among others) are formed so fast that the first intermediates in the lithiation sequence so far could not be elucidated. These results demonstrate clearly that replacement of two me₃Si groups in P₄(Sime₃)₄ by two me₃C groups excludes the rearrangement of LiP₄(Sime₃)(Cme₃)₂ to a P₇-molecule.     

Eine neue spektrophotometrische Kobaltbestimmung unter Verwendung der Bildung des Kobalt (II)-Calcichrom-Komplexes

Ohne Zusammenfassung     

Synthese und Struktur der Platin(O)-Verbindungen [(dipb)Pt]2(COD) und (dipb)3Pt2 sowie des clusters Hg6[Pt(dipb)]4 (dipb = (i-Pr)2P(CH2)4P(i-Pr)2)

Synthesis and Structure of the Platinum(0) Compounds [(dipb)Pt]₂(COD) and (dipb)₃Pt₂ and of the Cluster Hg₆[Pt(dipb)]₄ (dipb = (i-Pr)₂P(CH₂)₄P(i-Pr)₂) The reduction of (dipb)PtCl₂ with Na/Hg yields (dipb)Pt as an intermediate which reacts with the amalgam to form the cluster Hg₆[Pt(dipb)]₄ ( 3 ) or decomposes to (dipb)₃Pt₂ ( 2 ) and Pt. In the presence of COD [(dipb)Pt]₂(COD) ( 1 ) is obtained. 1 crystallizes monoclinicly in the space group P2₁/c with a = 1596.1(4), b = 996.5(2), c = 1550.4(3) pm, β = 113.65(2)°, Z = 2. In the dinuclear complex two (dipb)Pt units are bridged by a 1,2-η²-5,6-η² bonded COD ligand. Whereby the C = C double bonds are lengthened to 145 pm. 2 forms triclinic crystals with the space group P1 and a = 1002.0(2), b = 1635.9(3), c = 868.2(2) pm, α = 94.70(2)°, β = 94.45(2)°, σ = 87.95(1)°, Z = 1. In 2 two (dipb)Pt moieties are connected by a μ-dipb ligand in a centrosymmetrical arrangement. 3 is monoclinic with the space group C2/c and a = 1273.8(3), b = 4869.2(6), c = 1660.2(3) pm, β = 95.16(2)°, Z = 4. The clusters Hg₆[Pt(dipb)]₄ have the symmetry C₂. Central unit is a Hg₆ octahedron of which four faces are occupied by Pt(dipb) groups. The bonding in the cluster is discussed on the basis of eight Pt? Hg two center bonds of 267.6 pm and two Pt? Hg? Pt three center bonds with Pt? Hg = 288.0 pm.     

Die Strukturen der Heptahetero-Nortricyclene P7(Sime3)3 und P4(Sime2)3

The Structures of the Heptahetero-Nortricyclenes P₇(Sime₃)₃ and P₄(Sime₂)₃ Tris(trimethylsilyl)heptaphospha-nortricyclene P₇(Sime₃)₃ 1 and Hexamethyl-trisila-tetraphospha-nortricyclene P₄Si₃me₆ 2 are structural analogons to the hetero-nortricyclenes P and P₄S₃. 1 crystallizes in the space group P2₁ with a = 965.7 pm, b = 1746.5 pm, c = 693.3 pm, β = 99.61° and Z = 2 formula units. In the P₇ system tge P? P bond lengths differ functionally, namely 221.4 pm in the three-membered ring, 219.2 pm at the ring atoms and 217.9 pm at the bridgehead atom. The P? Si and Si? C bond lengths are 228.8 pm and 187.8 pm respectively. 2 crystallizes in the space group R3 with a_R = 1129.3 pm, α_R = 50.01° (hexagonal axes: a = 954.7 pm, c = 2956.9 pm) and Z = 2 formula units. In the P₄Si₃ systems the bond lengths are P? P = 220.2 pm, P? Si = 228.3 pm and 224.7 pm (to the bridgehead atom). The Si? C bond lengths are 187.3 pm. The structures are discussed with related compounds.     

Synthese der Clathratverbindungen des Typs Cd(en)Pd(CN)4·2G

In this paper three compounds with the same host molecule of Cd(en)Pd(CN)₄ type, but of different organic components such as thiophene, pyrrole and furan were described.