15 Fakultätsübergreifend / Sonstige Einrichtung

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1985 - 1989171990 - 199413

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Publication Type: search.filters.UBSTyp.ZeitschriftenartikelAuthor: search.filters.author.Gudat, Dietrich

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    Zur Elektronenstruktur von Phosphor(III)-p-π-Bindungssystemen: UV- und PE-spektroskopische Untersuchungen an Methylenphosphanen vom Typ R-P=C(SiMe3)2
    (1987) Gudat, Dietrich; Niecke, Edgar; Sachs, Werner; Rademacher, Paul
    Die UV- und die He-I-Photoelektronenspektren der Methylenphosphane R-P=C(SiMe3)2 3 (R = Cl, F, OBut, NHBut, SBut, NHSiMe3, NEt2, NPri2, 2,2,6,6-Me4C5H6N, N(But)SiMe3, N(SiMe3)2, Me, But) werden diskutiert. Die Zuordnung der Ionisationspotentiale zu π(P=C)- bzw. n(P)-Orbitalen ist konsistent mit den UV-Daten sowie semieempirischen MNDO-Rechnungen. Die π-Akzeptorwirkung der Silylsubstituenten bewirkt bei den alkylsubstituierten Verbindungen 31,m eine Umkehr der Abfolge der π(P=C)- und n(P)–I.P.'s im Vergleich zu bisher untersuchten Phosphaalkenen sowie theoretischen Vorhersagen. Einführung von RO- bzw. RS-Substituenten in 3c,d führt zur Ausbildung eines mesomeriestabilisierten 3-Zentren-4-Elektronen-π-Bindungssystems. Bei den Aminomethylenphosphanen 3e-k können in Abhängigkeit von der Raumerfüllung der Substituenten zwei unterschiedliche Konformere unterschieden werden, die sich durch die Stellung des Aminrestes bezüglich der Molekülsymmetrieebene unterscheiden. Die Koexistenz beider Konformere kann am Beispiel von 3h durch temperaturabhängige UV-Untersuchungen belegt werden. Die bemerkenswerten Unterschiede der 31P- und 13C-NMR-Daten von 3e-k können im Zusammenhang mit der beobachteten Konformationsisomerie erklärt werden.
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    Metallophospha-alkenes: a simple access and some reactivities involving the phosphorus atom
    (1985) Gudat, Dietrich; Niecke, Edgar; Malisch, Wolfgang; Hofmockel, Ullrich; Quashie, Sapé; Cowley, Alan H.; Arif, Atta M.; Krebs, Bernt; Dartmann, Mechtild
    The synthesis and studies on the reactive behaviour of metallophospha-alkenes are reported.
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    Coordination isomerism in pentamethylcyclopentadienyl-substituted iminophosphanes: from classical structures to a π-complexed iminophosphenium ion
    (1992) Gudat, Dietrich; Schiffner, Hans M.; Nieger, Martin; Stalke, Dietmar; Blake, Alexander J.; Grondey, Hiltrud; Niecke, Edgar
    Novel iminophosphanes of the type (Me5C5)P=NR [R = C6H2tBu3 (5a), Si-i-Pr3 (5b), SiMe3 (5c)] are prepared via either thermolytic or base-promoted elimination reactions and characterized by analytical and spectroscopic methods. The x-ray crystal structures of 5a,b establish the presence of coordination isomerism of the cyclopentadienyl ring, which at the same time strongly alters the characteristics of the P-N multiple bond. For 5a, η1-attachment of the Me5C5 moiety to the phosphorus and a localized phosphorus-carbon σ-bond are found, and the P-N double bond compares to that of alkylated iminophosphanes (rPN = 155.1 (8) pm). 5b exhibits η2-coordination of the cyclopentadienyl ring leading to increased P-N triple-bond character, as evidenced by shortening of the P-N distance (153.3 (3) pm) and the remarkable opening of the nitrogen valence angle (153.3 (2)°). The structure is discussed as an intramolecular π-complex between a formal cyclopentadienyl anion and an iminophosphenium cation. The 1H and 13C NMR spectra show that rapid elementotropic rearrangements around the five-membered ring take place both in solution and in the solid state. The unique temperature dependence of δ31P in solution together with the considerable differences in δ 31P between the solution and solid states are interpreted in a model assuming a "haptotropic" mechanism for the fluxionality involving dynamic η1/η2-coordination isomerizations in solution. As expected, nucleophilic displacement of the Me5C5 moiety takes place in the reaction of 5b,c with LiC6H2tBu3, yielding the iminophosphanes tBu3H2C6P=NR (R = Si-i-Pr3 (8b), SiMe3 (c)) as products.
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    Azasilatrane methanolysis pathways: stereoelectronic influences
    (1990) Gudat, Dietrich; Verkade, John G.
    Trigonal-bipyramidal azasilatranes of the type ZSi(NHCH2CH2)3N (Z = H, Me, OEt) solvolyze in MeOH to give N(CH2CH2NH2)3 (tren) and ZSi(OMe)3. Whereas intermediates in this reaction are not detected, ZSi[N-(SiR3)CH2CH2]3N species afford detectable intermediates of the type ZSi[N(SiR3)CH2CH2]n(NHCH2CH2)3-nN (n = 1, 2) before complete conversion to tren and ZSi(OMe)3 occurs. In cases where steric encumbrances weaken the Si-Nax bond in these molecules, monocyclic intermediates are detected. In contrast, methanolysis of HSi[N(BMe2)CH2CH2]3N gives N(CH2CH2NHBMe2)3 (and HSi-(OMe)3), which in the presence of CD3OD gives (CD3O)nSi(OMe)4-n and the novel adduct N-[CH2CH2NHD·B(OCD3)Me2]3. The possible steric and electronic influences of the equatorial substituents on the solvolysis pathways are discussed.
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    Transfer of a pentamethylcyclopentadienyl ligand from phosphorus to nickel: generation and spectroscopic characterization of the first examples of metalloiminophosphanes [(η5-Me5C5)(R3P)Ni-P=NBut](R = Et, Bu, or Ph)
    (1987) Gudat, Dietrich; Niecke, Edgar
    Reaction of (Me5C5)P=NBut with [(R3P)2Ni(cod)](cod = cyclo-octa-1,5-diene)(R = Et, Bu, or Ph) produces complexes [(R3P)2Ni(C5Me5)P=NBut], which rearrange to yield the novel metal-substituted iminophosphanes, [(R3P)(η5-C5Me5)Ni–P=NBut] and free phosphane R3P, the new complexes being identified by means of n.m.r. spectroscopy; similarly, the metallophospha-alkenes, [(R3P)(η5-C5Me5)Ni–P=C(SiMe3)2] are formed via reaction of (Me5C5)P=C(SiMe3)2 and [(R3P)Ni(alkene)2].
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    Reaction of (pentamethylcyclopentadienyl)(tert-butylimino)-phosphane with tris(acetonitrile)tricarbonylmolybdenum(0): evidence for a metalloiminophosphane intermediate
    (1986) Gudat, Dietrich; Niecke, Edgar; Krebs, Bernt; Dartmann, Mechtild
    (η1-Me5C5)P=N(t-Bu) (1) was prepared in a two-step synthesis from Me5C5PCl2. Reaction of 1 with (MeCN)3Mo(CO)3 affords the spirocyclic compound (η1-Me5C5PN(t-Bu)PN(T-Bu)C(O)Mo(CO)2(η5-C5Me5) (5), whose structure was determined by x-ray crystallography. A metalloiminophosphine, (η5-Me5C5)(CO)3MoP=N(t-Bu) (7), is proposed to be the key intermediate in the formation of 5.
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    Reaktionen eines Iminophosphoranylidencarbenoids
    (1994) Schilbach, Wolfgang; Gönna, Volker von der; Gudat, Dietrich; Nieger, Martin; Niecke, Edgar
    Interessante Abfangprodukte mit Phosphanen und Chlortrimethylsilan bildet das neuartige intermediär gebildete Phosphoranylidencarbenoid 1: Mit PPh3 entsteht das Phosphoniomethanid 2, mit PMe3 das Dihydrodiphosphet 3 und mit ClSiMe3 bildet sich das Imino(methylen)phosphoran 4. R = 2,4,6-tBu3C6H2, R′ = Ph, Me.
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    Iminophosphanes: unconventional compounds of main group elements
    (1991) Niecke, Edgar; Gudat, Dietrich
    The large number of known stable compounds in which phosphorus has a low coordination number makes it clear that such compounds can no longer be regarded as "exotic" in main group chemistry. While the rich chemistry of P-C multiply bonded systems makes clear their affinity to their organic congeners, iminophosphanes in particular are also of increasing importance. The linkage of a phosphinidine fragment with an imine fragment via a multiple bond gives rise to a class of compounds with an unusually wide range of structural types. This in turn leads to a broad spectrum of chemical behavior which makes iminophosphanes extremely useful synthetic building blocks in organoelement chemistry.
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    Reaction of P-halogeno-phospha-alkenes with alkene complexes of nickel and platinum: η2-co-ordination and unusual oxidative addition behaviour
    (1989) Gudat, Dietrich; Meidine, Mohamed F.; Nixon, John F.; Niecke, Edgar
    Phospha-alkenes X-P=CTMS2(X = F, Cl, I; TMS = SiMe3) display different reaction behaviour towards metal complexes (Bu3P)2Ni(cod)(cod = cyclo-octa-1,5-diene) or (Ph3P)2Pt(C2H4), respectively, undergoing either co-ordination to give η2-phospha-alkene complexes or alternatively oxidative addition of the P-X bond, forming phospha-alkenyl-metal(II) complexes, [(R3P)2M(X)(σ-P=CTMS2)].
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    Multinuclear magnetic resonance study of sterically crowded stannylphosphines and stannylamines : stereochemical influences on chemical shielding and spin-spin couplings
    (1994) Dörr, Armin; Gudat, Dietrich; Hänssgen, Dieter; Hens, Heribert; Stahlhut, Edith
    Multinuclear (1H, 15N, 29Si, 31P, 119Sn) NMR data of sterically crowded acyclic stannylphosphines tBu3SnPHY (Y = H, SnMe3, SntBu3, SiMe3; 1-3, 10), (tBu2RSn)2PH (R = Me, Cl; 4, 5), tBu3SnPY2 (Y = SnMe3, SiMe3; 6, 11), PH(SntBu2PHSntBu3)2 (7), SntBu2(PY2)2 (Y = H, SiMe3, PHSntBu3; 8, 9, 12), cyclic stannylphosphines (tBu2SnPY)n (n = 2, Y = H, C3H6Cl, tBu, SnMe3; 13-16; n = 3, Y = H; 18), (Me2SnPSntBu3)2 (17), and stannylamines tBu3SnNHY (Y = H, SnMe3, SntBu3; 19-21) were obtained by various 1D- and 2D-techniques. 31P- and 15N-shieldings may be explained qualitatively in terms of two counteracting influences, viz electronegativity differences and steric requirements of the substituents. In a similar manner, the trends in one-bond coupling 1KSnP and 1KSnM may be rationalized using a simple model based on the deformation of bond angles by sterically demanding substituents. The signs of long-range couplings 2KSnPH and 1KPSnCCH could be determined, which may be useful for future structural studies. Temperature-dependent effects in the spectra of 13, 18 allow conclusions about the conformational dynamics of the molecules.