15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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Item Open Access 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, PaulDie 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.Item Open Access 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, MechtildThe synthesis and studies on the reactive behaviour of metallophospha-alkenes are reported.Item Open Access 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, EdgarNovel 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.Item Open Access 31P NMR spectroscopic investigations of low-coordinated multiple bonded PN systems(1994) Niecke, Edgar; Gudat, DietrichIn this chapter, we attempt to give a systematic analysis of the influence on the 31P chemical shift and coupling 1JPN in terms of substituent effects, double-bond stereochemistry, and molecular dynamics for iminaphosphines and related compounds containing partial phosphorus-nitrogen triple-bond character. Although the main focus is on properties in the isotropic phase, reflecting that the majority of measurements were made in solution, the tensorial properties of the chemical shift as obtained from solid-state NMR measurements are also mentioned.Item Open Access 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, EdgarReaction 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].Item Open Access 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.Item Open Access Reaktionen eines Iminophosphoranylidencarbenoids(1994) Schilbach, Wolfgang; Gönna, Volker von der; Gudat, Dietrich; Nieger, Martin; Niecke, EdgarInteressante 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.Item Open Access Iminophosphanes: unconventional compounds of main group elements(1991) Niecke, Edgar; Gudat, DietrichThe 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.Item Open Access 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, EdgarPhospha-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)].Item Open Access Säurekatalysierte Isomerisierung des [2+1]-Cyclodimers eines Iminophosphans zum Diazadiphosphetidin(1986) Niecke, Edgar; Gudat, Dietrich; Symalla, ErhardNicht das Azadiphosphiridin 2, sondern das Diazadiphosphetidin 3 entsteht bei der Reduktion von 1. Das als Intermediat nachzuweisende 2 wird durch Lewis- oder Brønsted-Säuren in 3 umgewandelt. Mit F3CSO3H als Säure konnten die Zwischenstufen der Isomerisierung, 4 und 5, isoliert werden (R=tBu; X=F3CSO3).
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