Molecules organiques coordinees a un metal. : Nouveaux complexes olefiniques d'α-enones par le fer(0)

Heterodienetricarbonyliron complexes react with ligands ( L = PMe₂Ph, P(OMe)₃ or P(OPh)₃) to give the adducts (enone)Fe(CO)₃L with the ethylenic double bond coordinated only to the iron(0). Electron-releasing and low-steric effects of L make the reaction which is specific for enones easier compared to that for dienes. PMe₂Ph allows enone exchange and P(OPh)₃ promotes carbonyl elimination. Ligand influence is shown by infrared spectroscopy and by the shielding of ethylenic protons in NMR spectroscopy.     

Phénylhalogénohydrodigermanes

The symmetric and unsymmetric phenylchlorohydrodigermanes can be isolated or characterized via partial halogenation of the Ge? H bonds of the symmetrical phenylhydrodigermanes Ph₂(H)GeGe(H)₂Ph, Ph(H)₂GeGe(H)₂Ph by chloromethyl methyl ether and carbontetrachloride. Some of these phenylchlorohydrodigermanes are formed by insertion of phenylchlorogermylene (PhGeCl) on the Ge? H or Ge? Cl bonds of the phenylchlorohydrogermanes. The hydrolysis of the monochloro phenylhydrodigermanes Ph₂(Cl)GeGe(H)₂ and Ph(Cl)(H)GeGe(H)₂Ph leads to the phenyl phenylhydrogermyl digermoxanes [Ph₂(H)GeGePh₂]₂O and [Ph(H)₂GeGe(H)Ph]₂O. Treatment of these oxides with the concentrated aqueous solutions of hydracides leads to the monofluorinated, brominated and iodinated phenylhydrodigermanes Ph₂(H)GeGe(X)Ph₂ and Ph(H)₂GeGe(H)(X)Ph (X) = F, Br, I). Phenylchlorohydrodigermanes decompose thermally by α-elimination on one germanium atom with formation of germylene and phenylchlorohydrogermane. The physico-chemical IR. and NMR. study of these phenylhalogenohydrodigermanes indicates that, if the vGe? H frequency variations are mostly linked to the inductive effects of the substituents on the same germanium, the variations of the chemical shifts of the Ge? H protons seem to be due to many factors and especially to the inductive effect of the substituents on the germanium and the magnetic anisotropy of the Ge? X bonds.     

Nonlinear dynamics of the infinite classical Heisenberg model: Existence proof and classical limit of the corresponding quantum time evolution

For any initial spin configuration we prove the existence, unicity and regularity properties of the solution of Hamilton's equations for the infinite classical Heisenberg model with stable interactions, along with the essential selfadjointness of the associated Liouville operator. We also prove new properties of SU (2)-coherent states which, together with the concept of Trotter approximations for one-parameter (semi-) groups, are used to show that this dynamics is nothing but the classical limit of the time evolution generated by the infinite quantum (suitably normalized) Heisenberg Hamiltonian. The classical limit emerges when the spin magnitude S goes to infinity while Plank's constant goes to zero, their product S remaining fixed. The main results are stated in the form of intertwining relations between the classical and the quantum unitary group.Work supported in part by the Swiss National Science Foundation under Grant 820-436-76 and in part by the U.S. Department of Energy under contract EG-77-C-03-1538.     

Non-aqueous capillary electrophoresis of the positional isomers of a sulfated monosaccharide

A non-aqueous capillary electrophoresis (NACE) method coupled to indirect absorbance detection has been developed for the separation of the three positional isomers of monosulfated fucose. The optimized electrolyte was composed of 12 mM ethanolamine, 2 mM trimesic acid buffer in a methanol-ethanol (1:1, v/v) mixture. As the retained electrolyte entails no separating agent other than the pH buffer, the NACE separation of the positional isomers has been ascribed mainly to selective ion-pairing with the electrolyte counter-ion and the possibility of a selective solvation effect in the alcohol mixture. In the absence of pure isomeric standards, peak identification was completed by MS and NMR spectroscopy and selective enzymatic desulfation. This method should be of interest for the structure elucidation of monosulfated fucose-based polysaccharides and for the screening of sulfoesterase of unknown activity.     

Face Selectivity of the Diels-Alder Additions of 2-Substituted 5,6-bis((E)-chloromethylidene)bicyclo[2.2.2]octanes

The preparation of 5,6-bis((E)-chlorommethylidene)bicyclo[2.2.2]oct-2-ene ( 13 ), 2,3-bis((E)-chloromethyl idene)-5exo,6exo- and -5endo,6endo-epoxybicyclo[2.2.2] octane ( 14 and 15 ), 5,6-bis((E)-chloromethylidene)-2exo- and -2endo-bicyclo[2.2.2] octanol ( 16 and 17 ) and 5,6-bis((E)-chloromethylidene)-2-bicyclo[2.2.2]octanone ( 18 ) are described. The face selectivity (endo-face vs. exo-face attack onto the exo-cyclic diene) of their cycloadditions to tetracyanoethylene has been determined in benzene at 20°. It is 78/22, 80/20, 60/40, 68/32, 3/97 and 30/70 for 13 , 14 , 15 , 16 , 17 and 18 , respectively.     

Stereochimie de l'action des organomagnesiens et des organolithiens sur les dimethyl-1,2 alcoxy-1 silacyclobutanes

The reaction of organomagnesium organolithium compounds (alkyl, aryl, allyl and benzyl derivatives) with 1,2-dimethyl-1-alkoxy-l-silacyclobutanes proceeds with retention of configuration at the silicon atom. Stereochemical results are discussed in terms of the S_N2Si mechanism. The proposed configurations are supported by ¹H and ¹³C NMR data.     

Dirac's aether in relativistic quantum mechanics

The introduction by Dirac of a new aether model based on a stochastic covariant distribution of subquantum motions (corresponding to a vacuum state alive with fluctuations and randomness) is discussed with respect to the present experimental and theoretical discussion of nonlocality in EPR situations. It is shown (1) that one can deduce the de Broglie waves as real collective Markov processes on the top of Dirac's aether; (2) that the quantum potential associated with this aether's modification, by the presence of EPR photon pairs, yields a relativistic causal action at a distance which interprets the superluminal correlations recently established by Aspect et al.; (3) that the existence of the Einstein-de Broglie photon model (deduced from Dirac's aether) implies experimental predictions which conflict with the Copenhagen interpretation in certain specific testable interference experiments.     

A method for the systematic resolution of unbranched α-acetoxyalkyl- and aralkylaldehydes: synthesis of 11R and 11S-hete

It is shown that oxazolidines derived from racemic unbranched α-acetoxyaldehydes and ?-ephedrine have predictable chromatographic mobilities, with the R-isomer always having a higher R_f-value. This resolution has been used to prepare $\text{11R}$ and $\text{11S}$-HETE.     

Préparation d'isoxazoles trisubstitués par réduction chimique et électrochimique d'α-acyl β-nitrostilbènes

Nitration of α-acylstilbenes with dinitrogen tetroxide leads to corresponding Z-α-acyl-β-nitrostilbenes. By chemical or electochemical reduction of these compounds, trisubstituted isoxazoles were prepared in good yields.     

Etude des propriétés cristallographiques,diélectriques et d'optique non linéaire de quelques nouvelles phases de composition BaxLi5−2xNb5(1−y)Ta5yO15 et de structure bronzes oxygénés de tungstène quadratiques

Two series of phases with tetragonal bronze-like structure and composition Ba_xLi_5?2xT₅O₁₅ (T = Nb, Ta) have been isolated in the systems BaNb₂O₆LiNbO₃ and BaTa₂O₆LiTaO₃. All these phases show ferroelectric-paraelectric transitions. The Curie temperature increases with the lithium content. The value of T_C for Ba_2.03Li_0.94Nb₅O₁₅ is the highest ever observed for this type of structure: the obtained phases are potentially good materials for the harmonic generation of the 0.53-μm radiation. The optical yield of the niobate Ba_2.14Li_0.71Nb₅O₁₅ is about 2.5 times that of Ba₂NaNb₅O₁₅ and 250 times that of the K.D.P. The crystallographic and dielectric data of the system Ba_2.14Li_0.71Nb₅O₁₅Ba_2.14Li_0.71Ta₅O₁₅ characterize three domains, which are respectively antiferroelectric, ferroelectric, and paraelectric. The Curie temperature and the optical yield decrease with increasing tantalum content.