bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sur l'arôme de viande de boeuf grillée II. Dihydro‐6,7‐5H‐cyclopenta[b]pyrazines, identification et mode de formation
Authors: Flament Ivon , Kohler Margrit , Aschiero Roland 
Published: December 2004

Identification of alkyl‐5H‐6,7‐dihydrococyclopenta[b]pyrazines in roasted meat flavor. Model reaction used as basis for natural product formation and new synthesis.Seven alkyl‐5H‐6,7‐dihydrocyclopenta[b]pyrazines have been identified in a roasted meat aroma obtained by thermolysis of the hydrosoluble flavor precursors of raw meat. Formation of these heterocyclics by condensation of hydroxycyclopentenones with aliphatic α‐dicarbonyl compounds in the presence of ammonia has been confirmed by a model reaction.Alkyl‐5H‐cyclopenta[b]pyrazines and dicyclopenta [b,e]pyrazines are also obtained from this reaction, but have not yet been identified in roasted flavors. Preparation of the intermediates of the model reaction enabled development of an economical synthesis of 2,3,5‐trimethyl‐5H‐6,7‐dihydrocyclopenta[b]pyrazine.
13C‐Kernresonanzspektroskopische Untersuchungen an ionenselektiven Flüssigmembranen
Authors: Büchi Rolf , Presch Ernö , Simon Wilhelm 
Published: December 2004

13C‐NMR. Studies on Ion‐Selective Liquid Membranes.A method for the 13C‐NMR. study of solvent polymeric membranes in equilibrium with aqueous salt solutions is described. Neutral ion carriers incorporated in these membranes maintain a high degree of rotational mobility. The complexation by group IA and IIA cations of macrotetrolide antibiotics as well as of carriers of the type 3,6‐dioxa‐octanedioic diamides in the membrane phase was followed by 13C‐NMR. chemical shift and spin‐lattice relaxation studies.
Conformational Analysis and Chromic Acid Oxidation. Oxidation Rates and Equilibrium Constants of Epimeric Alcohols
Authors: Müller Paul , Perlberger Jean‐Claude 
Published: December 2004

AbstractThe linear free energy relationship of Sicher for relative reactivity towards chromic acid oxidation (ΔΔG) as a function of thermodynamic stability (ΔG) has been reexamined with 23 pairs of epimeric alcohols. The plot of ΔG vs. ΔG has a slope of 0.8, a correlation coefficient of 0.97 and a standard deviation of 0.23 kcal/mol on ΔΔGOx. The limitations of the relationship and the exceptions are discussed.
The Reaction of Difluorocarbene with Bicyclo[2.2.2]octadiene
Authors: Jefford Charles W. , Delay Arlette , Wallace Timothy W. , Burger Ulrich 
Published: December 2004

AbstractThe addition of difluorocarbene to bicyclo[2.2.2]octa‐2,5‐diene gave the exo and endo 1:1 cyclopropane adducts. In contrast to norbornadiene, no homo‐1,4 adduct was formed. The adducts were thermally stable under the conditions of their formation and separation (<170°). However, smooth equilibration was achieved on heating at 250° for 36 h. The same mixture resulted from either isomer. At 250° ΔΔG = 1.83 kcal/mol; the endo isomer being the more stable. Heating to higher temperatures caused decomposition, rather than further reaction to the intramolecular [2+2]cyclization products. The kinetic and thermodynamic product compositions were essentially the same on extrapolating to the same temperature, viz. endo/exo = 19–22 at 25°. The mechanisms by which the cyclo‐addition and the stereomutation of the cis‐fused cyclopropane moiety occur are discussed.
Isolement et identification de deux β‐carbolines dans la racine de chicorée torréfiée
Authors: Proliac Arlette , Blanc Maurice 
Published: December 2004

Isolation and identification of two β‐carbolins in roasted chicory roet.Two β‐carbolines, harman and norharman, have been isolated from roasted chicory roots by solvent extraction and chromatography on alumina. They have been identified by chromatographic and spectroscopic techniques in comparison with reference compounds.
Heterotricyclodecane XIX. Umlagerungen von 4,8‐disubstituierten 2,6‐Dioxa‐ und 2‐Oxa‐6‐aza‐adamantanen zu 4,10‐disubstituierten 2,7‐Dioxa‐ und 2‐Oxa‐7‐aza‐isotwistanen sowie ‐twistanen
Authors: Ackermann Peter , Portmann Robert Ernst , Ganter Camille 
Published: December 2004

Rearrangements of 4,8‐disubstituted 2,6‐dioxa‐ and 2‐oxa‐6‐aza‐adamantanes to 4,10‐disubstituted 2,7‐dioxa‐ and 2‐oxa‐7‐aza‐isotwistanes as well as ‐twistanes.Substitutions and rearrangements involving neighboring group participation starting from 4,8‐diiodo‐2,6‐dioxa‐ and 4,8‐diiodo‐2‐oxa‐6‐aza‐adamantanes (5 and 6, 12 and 48, resp.) were studied, yielding 4,8‐disubstituted 2,6‐dioxa‐ and 2‐oxa‐6‐aza‐adamantanes (7, 9, 39, 42 and 13, 15, 50, 52, resp.), 4,10‐disubstituted 2,7‐dioxa‐ and 2‐oxa‐7‐aza‐isotwistanes (8, 10, 41, 43 and 14, 16, 51, 53, resp.) and corresponding‐twistanes (11 and 17, resp.).
Reactions in the Acridone‐Fields.
Authors: Manukian Badrig K. 
Published: December 2004

Abstract1‐Chlor‐ und 1,7‐Dichlor‐4‐nitro‐acridon wurden mit einigen Phenolen und Bisphenolen zu Farbstoffen umgesetzt, die Polyvinylchlorid grünlichgelb färben. Im Xenotest 800 Std. belichtet, zeigten die einfachen Acridone IX bis XIII eine ungewöhnlich hohe Lichtechtheit; sie sind aber migrationsunecht. Eine Verdoppelung der Molekel (lineare Bisacridone) bewirkte eine bedeutende Verminderung der Löslichkeit, jedoch begleitet vom Verlust der hohen Lichtechtheit.
Über Pterinchemie 75. Mitteilung Synthese von 7‐Aminoxanthopterin
Authors: Baumgartner Konrad , Bieri Jost H. 
Published: December 2004

Synthesis of 7‐Aminoxanthopterin7‐Aminoxanthopterin (II) is obtained in good yield and purity by the transformation of isomer‐free xanthopterin‐7‐carboxylic acid (I) with NH3 followed by oxidation with MnO2. The Frontier Orbital Theory contributes to a better understanding of the reaction pathway.
Synthesis of 1‐Bicyclo [3.2.2]nonene and 1 (7)‐Bicyclo [3.2.2]nonene by Intramolecular Wittig Reaction
Authors: Becker Konrad B. , Chappuis Jacques L. 
Published: December 2004

AbstractThe synthesis of 1‐bicyclo[3.2.2]nonene (2) and of 1 (7)‐bicyclo [3.2.2]nonene (3), two isomeric bridged (E)‐cycloheptenes, by intramolecular Wittig reaction is described. These ‘Bredt olefins’ could not be isolated, but dimerized rapidly. In both cases, the main product was shown to be a head‐to‐tail dimer with a cyclobutane ring. The ‘Bredt olefins’ were also trapped in situ with furan or 2,5‐diphenylbenzo [c]furan.
Alkaloid Production in Catharanthusroseus Cell Cultures. IV. Characterization of the 953 Cell Line
Authors: Kurz Wolfgang G. W. , Chatson Kenneth B. , Constabel Friedrich , Kutney James P. , Choi Lewis S. L. , Kolodziejczyk Pawel , Sleigh Stephen K. , Stuart Kenneth L. , Worth Brian R. 
Published: December 2004

AbstractThe 953 cell line, one of the cell lines from Catharanthus roseus, has been investigated in terms of its ability to produce indole alkaloids. Various parameters (mitotic index, pH, cell dry weight, growth period) were evaluated in the fermentation process and their relative importance for alkaloid production was determined. The alkaloids isolated and identified are ajmalicine, yohimbine, isositsirikine, vallesiachotamine, strictosidine lactam, lochnericine, hörhammericine, hörhammerinine, vindolinine, 19‐epivindolinine, 19‐acetoxy‐11‐methoxytabersonine, 19‐hydroxy‐11‐methoxytabersonine and dimethyltryptamine.
Laser Induced Excitation Spectra of the Cations of Some Fluoro‐substituted Phenols (B̃2 A″ ↔ X̃2 A″) in the Gaseous Phase
Authors: Maier J. P. , Misev L. , Shiley R. H. 
Published: December 2004

AbstractExcitation spectra of the cations of pentafluorophenol, 2,3,4‐trifluorophenol, 2,4,5‐trifluorophenol, 2,5‐difluorophenol and 3,5‐difluorophenol have been obtained by pumping the B̃2 A″ ← X̃2A″ transition with a dye laser. The cations were first produced in their ground states by Penning ionisation using argon metastables. Vibrational frequencies of some of the fundamentals have been inferred for these cations in the B̃2 A″ state from the excitation spectra, and in the X̃2 A″ state from the emission spectra. Possible applications of the reported results are suggested.
Heterodiamantanes and Structurally Related Compounds. Part II: The Pentacyclic C10‐Diethers 5,12‐Dioxapentacyclo [6.4.0.02,6.03,11.04,9]dodecane and 4,12‐Dioxapentacyclo[6.3.1.02,7.03,10.05,9]dodecane
Authors: Ammann Willi , Jäggi Franz Josef , Ganter Camille 
Published: December 2004

AbstractIn connection with studies on heterodiamantanes and structurally related compounds the two novel pentacyclic diethers 9 and 10 were prepared starting from the photo‐dimer 8 of cyclopentadienone. All three compounds have as common features a central carbocyclic 6membered ring with four axial alkyl substituents and two oxygen function in 1,4‐position. The diether 9 was obtained on the one hand from the intermediate tetracyclic unsaturated alcohol 23 by intramolecular addition, catalyzed either by acid or base (scheme 3), and on the other hand from the tetracyclic diol 32 or the dibromoketones 34 (via 38) and 35 (via 39) by intramolecular substitution (schemes 4 and 5). The synthesis of the isomeric diether 10 was achieved by intramolecular substitution of the tetracyclic diol 33 (scheme 4). Diether 9 is thermodynamically more stable than 10. The latter was easily isomerized to the former on treatment with concentrated sulfuric acid in benzene.
Tricyclo [3.3.2.03,7]decan (9‐Homo‐nor‐adamantan) Synthese und Umwandlungen
Authors: Jäggi Franz Josef , Ganter Camille 
Published: December 2004

Tricyclo[3.3.2.03,7]decane (9‐Homo‐nor‐adamantane). Synthesis and TransformationsA synthesis of tricyclo [3.3.2.03,7]decane (=9‐homo‐nor‐adamantane; 1), which belongs to the adamantaneland, a family of nineteen isomeric C10H16 hydrocarbons, is described, as well as derivatives thereof. Treatment of protoadamantan‐5endo‐ol (11) with either thionyl chloride or phosphorus pentachloride yielded under rearrangement the chloride 18, and solvolysis of the 5endo‐chloro‐protoadamantane (16) led to the acetate 26, 18 and 26 having both the tricyclo [3.3.2.03,7]decane skeleton. Subsequent transformations gave the title compound 1 as well as the corresponding olefin 8.
Aristoserratin, ein neues Indolalkaloid aus Aristotelia serrata W.R.B. OLIVER und A. peduncularis (LABILL.) HOOK. F. 178. Mitteilung über organische Naturstoffe
Authors: Hai Mohammad A. , Preston Nigel W. , Kyburz Rolf , Schöpp Emanuel , Bick I. Ralph C. , Hesse Manfred 
Published: December 2004

Aristoserratine, a New Indole Alkaloid from Aristotelia serrata W.R.B. OLIVER and from A. peduncularis (LABILL.) HOOK. F.The new indole alkaloid aristoserratine (2) has been isolated from Aristotelia. Its structure and absolute configuration were elucidated on the basis of spectroscopic data.
Azimine IV. Kinetik und Mechanismus der thermischen Stereoisomerisierung von 2,3‐Diaryl‐1‐phthalimido‐aziminen
Authors: Hoesch Lienhard 
Published: December 2004

Azimines IV. Kinetics and Mechanism of the Thermal Stereoisomerization of 2,3‐Diaryl‐1‐phthalimido‐azimines1)Mixtures of (1E, 2Z)‐ and (1Z, 2E)‐2‐phenyl‐1‐phthalimido‐3‐p‐tolyl‐azimine (3a and 3b, resp.) and (1E, 2Z)‐ and (1Z, 2E)‐3‐phenyl‐1‐phthalimido‐2‐p‐tolylazimine (4a and 4b, resp.) were obtained by the addition of oxidatively generated phthalimido‐nitrene (6) to (E)‐ and (Z)‐4‐methyl‐azobenzene (7a and 7b, resp.). Whereas complete separation of the 4 isomers 3a, 3b, 4a and 4b was not possible, partial separation by chromatography and crystallization led to 5 differently composed mixtures of azimine isomers. The spectroscopic properties of these mixtures (UV., 1H‐NMR.) were used to determine the ratios of isomers in the mixtures, and served as a tool for the assignment of constitution and configuration to those isomers which were dominant in each of these mixtures, respectively.Investigation of the isomerization of the azimines 3a, 3b, 4a and 4b within the 5 mixtures at various concentrations by 1H‐NMR.‐spectroscopy at room temperature revealed that only stereoisomers are interconverted (3a ⇄ 3b; 4a ⇄ 4b) and that the (1E, 2Z) ⇄ (1Z, 2E) stereoisomerization is a unimolecular reaction. These observations exclude an isomerization mechanism via an intermediate 1‐phthalimido‐triaziridine (2) or via dimerization of 1‐phthalimido‐azimines (1), respectively. The 3‐p‐tolyl substituted stereoisomers 3a and 3b isomerized slightly slower than the 3‐phenyl substituted ones 4a and 4b, an effect which is consistent with the assumption that the rate determining step of the interconversion of (1E, 2Z)‐ and (1Z, 2E)‐1‐phthalimido‐azimines (1a ⇄ 1b) is the stereoisomerization of the stereogenic center at N(2), N(3), either by inversion of N(3) or by rotation around the N(2), N(3) bond. The total isomerization process is assumed to occur via the thermodynamically less stable (1Z, 2Z)‐ and (1E, 2E)‐isomers 1c and 1d, respectively, as intermediates in undetectably low concentrations which stay in rapidly established equilibria with the observed, thermodynamically more stable (1E, 2Z)‐ and (1Z, 2E)‐isomers 1a and 1b, respectively.At higher temperatures, the azimines 3 and 4 are transformed into N‐phenyl‐N,N′‐phthaloyl‐N′‐p‐tolyl‐hydrazine (8) with loss of nitrogen.
Physico‐Chemical Properties of Deuterated Compounds. 5th Communication. The isotope partition coefficient in cyclohexane hydrogen and cycloheptane/hydrogen mixtures
Authors: Dessauges Gëarald , Gäumann Tino 
Published: December 2004

AbstractThe isotope partition coefficient α between cyclohexane, cycloheptane and hydrogen has been determined between 80 and 180° and pressures around 1 atm. The values decrease with increasing deuterium content y of the hydrogen and can be expressed by the simple equation Ina = Δ S/R + (ΔH + δ · y)/RT with an error of ±1%. However it was not possible to achieve good agreement with theoretical calculations using a unique average value for the partition function of the hydrocarbon.
New Dienophiles: 1‐Acetylvinyl Arenecarboxylates. Reactivity toward cyclopentadiene and exocyclic dienes
Authors: Tamariz Joaquin , Vogel Pierre 
Published: December 2004

AbstractThe preparations of 1‐acetylvinyl arenecarboxylates H2C=C(COCH3)OCOR with R = phenyl,p‐nitrophenyl, 2,4‐dinitrophenyl, α‐ and β‐naphthyl are described(3). TheDiels‐Alderreactivity of these dienophiles toward cyclopentadiene is evaluated and compared with that of methyl vinylketone, 3‐trimethylsilyloxy‐, 3‐ethoxy‐ and 3‐acetoxy‐3‐buten‐2‐ones. The stereoselectivity of the cycloadditions of these dienophiles with 2,3,5,6‐tetramethylidene‐7‐oxanorbornane(1)and 5,8‐dimethoxy‐1,4‐epoxy‐2,3‐dimethylidene‐1,2,3,4‐tetrahydroanthracene(2)is studied. In principle, the dienophiles3allow direct functionalization of the position C(9) of the A‐ring of daunomycinone analogs byDiels‐Alderadditions to exocyclic dienes such as1and2.
Partial Synthesis of 3′‐Hydroxy‐2′‐deoxy‐2″,3″,4″,5″‐tetrahydroverrucarin A. Verrucarins and roridins, 38th Communication [1]
Authors: Notegen Eric‐Andréa , Tori Motoo , Tamm Christoph 
Published: December 2004

AbstractThe macrocyclic trichothecene triester 3′‐hydroxy‐2′‐deoxy‐2",3",4",5"‐tetrahydroverrucarin A (37), has been synthesized starting from the sesquiterpene alcohol verrucarol (3), adipic acid and a derivative of mevalonic acid (14). The latter has been prepared from 4‐(tetrahydro‐2‐pyranyloxy)‐2‐butanone (9).
The Synthesis of Some 7, 8‐Dimethoxy‐5‐phenyl‐2H‐3‐benzazepin‐2‐one Derivatives
Authors: Berney Daniel , Schuh Karlheinz 
Published: December 2004

AbstractThe benzazepin‐2‐ones 7 and 9 were prepared from homoveratroyl chloride (4) and phenacylamine. Compounds 7 and 9 were used for the preparation of the benzazepin‐2‐amines 3, 11, 13 and 14. A synthesis of the benzazepine‐1,2‐dione 17 and the benzazepine‐2,4‐dione 20 is also described.
Crystal Structures of 8‐Methoxy‐ and 8‐Nitronaphthonitrile; Intramolecular Nucleophile‐electrophile Interactions
Authors: Procter Garry , Britton Doyle , Dunitz Jack D. 
Published: December 2004

AbstractThe crystal structures of 8‐methoxy‐1‐naphthonitrile and 8‐nitro‐1‐naphthonitrile have been determined by X‐ray analysis. The methoxynitrile molecule shows a distortion pattern that is essentially similar to that found previously in other 1,8‐disubstituted naphthalenes with Nu…CO interactions; instead of non‐planarity at the carbonyl C‐atom there is bending at the the cyano C‐atom. Crystals of the nitronitrile contain two symmetry‐independent molecules that differ in structure; both show bent cyano groups, short O…CN distances, and asymmetric nitro groups, but in different degree. There is no clear correlation between the amount of any given distortion and the strength of the nucleophile‐electrophile interaction.
On the Relation between One‐Bond Coupling Constants and the s‐Electron Density at the Nucleus
Authors: Mitchell Terence N. , El‐Behairy Mostafa 
Published: December 2004

AbstractA comparison of Mössbauer isomer shifts and direct Sn, Sn‐coupling constants for a series of di‐ and polytin compounds indicates that the s‐electron density at the Sn‐atom has little influence on this coupling.
Nucleophilic Addition to C, C‐Double Bonds. IV. Ether formation by intramolecular addition to unsymmetrically alkyl‐substituted C, C‐double bonds
Authors: Ramos Tombo Gerardo M. , Pfund Rolland A. , Ganter Camille 
Published: December 2004

AbstractTricyclic olefinic alcohols containing an unsymmetrically alkyl‐substituted C, C‐double bond were cyclized intramolecularly to their corresponding ethers under basic conditions: 9 → 12, 10 → 17 + 18, and 11 → 12 (Scheme 3, Table 1). The reactivity is mainly due to relieve of ground state strain.Alcohol 9 (endocyclic double bond) isomerized under intramolecular assistance by the hydroxyl group to 11 (exocyclic double bond) before cyclization to 12 occurred (Scheme 5). The latter step being the faster one, no isomerization 11 → 9 was observed.
Loss of H2O from M + t‐Butyl Complex Ions of Benzyl Alcohol in Isobutane Chemical Ionization Mass Spectrometry
Authors: Liehr Joachim G. , Brenton Gareth A. , Beynon John H. , McCloskey James A. , Blum Wolfgang , Richter Wilhelm J. 
Published: December 2004

AbstractIn isobutane chemical ionization mass spectrometry benzyl alcohol exhibits ions at m/z 147 (‘M + 39’) that arise by a loss of H2O from [M + C4H9]+, i.e. ‘M + 57’ complex ions. Electrophilic aromatic substitution of a proton at an ortho‐position of neutral C6H5CH2OH with [t‐C4H9]+ and, alternatively, nucleophilic substitution of H2O at the benzylic carbon in \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C_6 H_5 CH_2}\mathop {\rm O}\limits^+ {\rm H}_2 $\end{document} with CH2C (CH3)2 are discussed as possible pathways. Evidence in favor of the latter is derived from the analysis of C6D5CH2OH and C6H5CD2OH for the origin of the H‐atoms lost in H2O. The inferred ion structure of m/z 147 is verified by mass‐analyzed ion kinetic energy (MIKE.) measurements of its collision‐activated (CA.) decomposition. MIKE./CA. spectra of mass‐selected m/z 147 ions, once generated by (CI(i‐C4H10) from benzyl alcohol and, once, from 2‐methyl‐4‐phenyl‐2‐butanol match closely and, thus, reflect identical ion structures. With reference to the simple genesis of this ion from the latter precursor, the structure in question can be concluded to be \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C_6 H_5 CH_2 CH_2}\mathop {\rm C}\limits^+ ({\rm CH}_3)_2 $\end{document}
.
Conformational Dependence of One‐Bond Cα,H Spin Coupling in Cyclic Peptides
Authors: Egli Huldrych , Von Philipsborn Wolfgang 
Published: December 2004

AbstractConformational effects on the one‐bond Cα, H coupling constant have been studied in cyclic oligopeptides containing glycine, alanine, sarcosine and proline. The conformational contribution to 1J (Cα, H) can be described as being composed of a positive hyperconjugative term from the neighbouring N‐pz orbital and a negative one from the carbonyl π‐system. For glycyl units, a quantitative relation between 1J (Cα,H) and the vicinal interorbital angles Φ′ and Ψ′ is derived with maximum values ΔJ (Ψ′) = + 14.0 Hz and ΔJ (Ψ′) = −4.9 Hz. Applications to conformational analysis of cyclo (L‐Pro‐Gly)3, cyclo (D‐Ala‐D‐Ala‐L‐Ala‐D‐Ala‐L‐Ala‐L‐Ala) and cyclo (Sar)8 are presented.
Some Observations Concerning 1H‐NMR. Spectra of 5‐hydroxy‐ and 5‐acetoxy‐steroid compounds
Authors: Mihailović Mihailo Lj. , Lorenc Ljubinka , Pavlović Vladimir , Fuhrer Hermann 
Published: December 2004

AbstractIt was found that analysis of the 1H‐NMR. signals (at 360 (preferably) and/or 100 MHz) of the protons at C (4) and of the equatorial α‐proton at C (6), particularly when these are located in the 2–3 ppm region and therefore convenient for detection and identification, may be of valuable aid in the structural and configurational characterization of 5‐hydroxy‐ and 5‐acetoxy‐steroids (unsubstituted or containing a hydroxy or acyloxy substituent at C (3)).
Cryptates Sphériques. Synthèse et Complexes d'Inclusion de Ligands Macrotricycliques Sphériques
Authors: Graf Ernest , Lehn Jean‐Marie 
Published: December 2004

Spherical Cryptates. Synthesis and Inclusion‐Complexes of Spherical Macrotricyclic LigandsA general strategy for the synthesis of spherical macrotricyclic ligands has been developed. Four spherical cryptands, SC‐24, SC‐25, SC‐26 and SC‐27 have been obtained by this route. The synthesis and cation‐complexing properties of these compounds are described in detail. Stability constants and cation exchange rates of the spherical cryptates obtained with alkali and alkaline‐earth cations have been determined. Highly stable complexes are formed by SC‐24; the Rb+ and Cs+ cryptates of SC‐24 are the most stable complexes of these cations known to date. The size of the intramolecular cavity affects the complexation selectivity. The cation exchange rates are very slow, and the corresponding free energies of activation are even larger than, for macrobicyclic cryptates of similar stability. Both the high complex stabilities and the high activation energies required for cation exchange indicate a marked ‘spherical cryptate effect’ resulting from the highly connected nature of the molecular architecture of spherical macrotricyclic ligands.
119Sn‐ and 31P‐NMR. Spectroscopy of the 5‐coordinate complexes [Rh (SnClnBr(3−n)) (norbornadiene) (tertiary phosphine)2]
Authors: Garrlda Maria , Garcia Victoria , Kretschmer Matthias , Pregosin Paul S. , Ruegger Heinz 
Published: December 2004

AbstractThe products of the reaction of [RhCl (NBD)]2 (NBD = norbornadiene), with four equivalents tertiary phosphine and two equivalents of tin (II) bromide have been studied by 119Sn‐ and 31P‐NMR. spectroscopy. The solution data suggest that halogen scrambling occurs during the preparation and results in a mixture of complexes containing SnBr3, SnClBr2, and SnCl2Br and SnCl3 ligands, and this is confirmed by independent synthesis of the SnCl3 and SnBr3 complexes. The metalmetal coupling constants, 1J (119Sn, 103Rh), vary from 452 to 580 Hz and are linearly related to: (a) δ(119Sn) in the complexes [Rh (SnClnBr(3‐n))NBD (PEtPh2)2] and (b) the sum of the Pauling electronegativities for the halogens on tin.
A Comparative Study of Platinum Di (t‐butyl) (15N2)diimine and trans‐[(PtCl2(N‐ligand)PBu3)] complexes by 195Pt‐, 31P‐ and 15N‐NMR
Authors: van der Poel Henk , van Koten Gerard , Grove David M. , Pregosin Paul S. , Starzewski Karl A. Ostoja 
Published: December 2004

Abstract195Pt‐, 31P‐ and 15N‐NMR. data are presented for [PtCl2 (t‐Bu 15NCHCH15N (t‐Bu)) (η2‐styrene)] (1), trans‐[{PtCl2 (PBu3)}2 (t‐Bu 15NCHCH15N (t‐Bu))] (2), trans‐[PtCl2 (t‐Bu 15NCHCH15N (t‐Bu)) (PBu3)] (3) and various complexes of the type trans‐[PtCl2 (N‐ligand) (PBu3)]. In solution the gross structural features of 1 and 2 are shown to be in agreement with those found in the solid state; namely, 1 contains five‐coordinate Pt and 2 is dinuclear. In 3 Pt is four‐coordinate with only one N‐atom of the diimine ligand being coordinated at −50° in CD2Cl2. The NMR. data for 2 and 3 are compared with those of trans‐[PtCl2 (N‐ligand) (PBu3)] (N‐ligand = pyridine, 2, 6‐dimethylpyridine, (15N)‐hexylamine, (15N)‐t‐butylamine and (15N)‐aniline) and are discussed in terms of the donor and acceptor properties of the N‐ligands.