Synthesis, crystal structure, and chirality of divalent lanthanide reagents containing tri- and tetraglyme

Six new divalent lanthanide complexes using triglyme (trigly) and tetraglyme (tetgly) as achiral ligands have been prepared, using a facile synthetic method, in search for enantioselective solid-state reagents. The crystal structures of cis-[SmI₂(trigly)thf] (1), trans-[YbI₂(trigly)thf] (2), trans-[SmI₂(trigly)dme] (3), trans-[YbI₂(tetgly)] (4), trans-[EuI₂(tetgly)thf] (5), and [Sm(tetgly)₂][SmI₃(tetgly)]I (6) have been determined. All complexes, except 5, are chiral. The 10-coordinate cation in 6 displays a helical chirality since the two tetraglyme ligands are wrapped around the samarium ion. Since trans-[YbI₂(tetgly)] (4), which has a chiral arrangement of terminal methyl groups, crystallizes as a conglomerate, preferential crystallization and consequent enantioselective reduction of acetophenone was attempted, but resulted in racemic products, possibly on account of racemic twinning in 4.     

Die Reaktionen von Eisen(III)-chlorid mit Trithiazylchlorid. Die Kristallstruktur von [S4N4Cl]+[FeCl4]⊖

Reactions of Iron Trichloride with Trithyazyl Chloride. Crystal Structure of [S₄N₄Cl]⁺[FeCl₄]^? Iron trichloride reacts with (NSCl)₃ yielding S₄N₄[FeCl₄]₂, S₃N₃Cl₂[FeCl₄] or S₄N₄Cl[FeCl₄], depending on the reaction conditions. The i.r. spectra prove the presence of [FeCl₄]^? ions for all three compounds. The ⁵⁷Fe-Mössbauer spectra show a slight quadrupole splitting at 80 K for S₃N₃Cl₂[FeCl₄] (ΔE^Q = 0.42 mm · s^?1) and S₄N₄Cl[FeCl₄] (ΔE^Q = 0.23 mm · s^?1), which indicates a slight deformation of the FeCl₄^? tetrahedra. The crystal structure of S₄N₄Cl[FeCl₄] was determined and refined with X-ray diffraction data (2549 independent reflexions, R = 0.026). S₄N₄Cl[FeCl₄] crystallizes in the triclinic space group P1 with two formula units per unit cell. The lattice constants are a = 712, b = 911, c = 1006 pm, α = 76.5°, β = 83.8° and γ = 80.5°. The structure consists of the so far unknown [S₄N₄Cl]^⊕ cations and slightly deformed FeCl₄^? ions. The [S₄N₄Cl]^⊕ ion consists of a S₄N₄ ring built up of two nearly planar S₃N₂ fragments having a dihedral angle of 136°. The average SN bond length is 157 pm, the SCI bond length 214 pm.     

Über die Konfiguration des Prolins im Ergotamin

It is well known that in the ergot alkaloids of the peptide type the proline appears in thel-configuration. Different methods of acid hydrolysis may lead to various cleavage products; hydrolysis by HCl yieldsd-proline, on the other hand hydrolytic cleavage by means of strongly acid cation exchange resin preserved the orginall-configuration.

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Teilveröffentlichung der Dissertation vonH. Kolassa, Univ. Wien, 1973.     

Thermische Polymerisation von Acenaphthylen

Zusammenfassung Acenaphthylen wurde durch Anpolymerisation und zweifache Hochvakuumsublimation gereinigt. Die Reinigungsmethode wird ausführlich beschrieben.Bei verschiedenen Temperaturen wurde mit einer dilatometrischen Methode die thermische Bruttogeschwindigkeit gemessen. Zwischen 95 und 105 °C giltk _br=7,0₈·10¹⁰ exp (– 30,9 kcal/RT).Die beträchtliche Aktivierungsenergie der Bruttoreaktion ist sowohl auf eine große Aktivierungsenergie der thermischen Startreaktion als auch auf eine relativ hohe Wachstumsaktivierungsenergie zurückzuführen.Das Polymerisationsverhalten von Acenaphthylen kann vermutlich aufgrund seiner sterischen Eigenschaften erklärt werden.

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Summary Acenaphthylene was purified by partial polymerisation, followed by double stage high vacuum sublimation. The method of purification is described in detail.The thermal overall rate was measured at different temperatures by a dilatometric method. Between 95 and 105 °C the following relation holds:k _th=7,0₈ · 10¹⁰ exp (– 30,9 kcal/RT).The considerable energy of activation of the overall reaction depends on a relatively high energy of activation of both the thermal initiation and the propagation reaction.It is supposed, that the polymerisation behaviour of acenaphthylene depends mainly on its steric properties.

     

Deoxygenation of supporting electrolytes in stripping voltammetry by glocuse and co-immobilized glocuse oxidase and catalase in a flow system

Carrier solutions for stripping voltammetry in flow systems are deoxygenated by reaction with glucose added to the carrier. The reaction was catalyzed by glocuse oxidase and catalase co-immobilized in an enzyme reactor which was inserted before the injector. The oxygenated was removed at least as efficiently as with nitrogen purging and the voltametric behaviour of cadmium(II), lead(II) and zinc(II) was unaffected by the glucose/gluconic acid system. A particular advantage is the rapid start-up compared to the lengthy purging of carrier solution when nitrogen degassing is used. The enzyme reactor made from porous glass was effective for several months.     

A field theoretical description of states with different orbitals for different spins

A field theoretical formulation is given for the method of different orbitals for different spins (DODS ). For an infinite system DODS describes an antiferromagnetic state and to account for this spin ordering a Gorkov-type of factorization is introduced. A corresponding gap equation is derived, where a non-zero solution indicates the presence of long-range order in the system. Actually the formulation given is general enough as to render DODS as a special case. As shown, we may also obtain a ferrimagnetic as well as a density wave state solution depending on the special characteristics of the system at hand. A related type of antiferromagnetism is described by the Overhauser spin density wave (SDW ) state and also this theory is formulated in a field theoretical language. The similarities and differences between DODS and SDW are discussed. The energy expressions for the two states are given within the Hartree-Fock approximation. It is proposed that the SDW state could be used to partly account for the correlation problem in molecules, as well as the method of DODS which has previously been employed for that purpose.     

New rhenium-tin cluster adds palladium phosphine groups across Re-Sn bonds

The new rhenium-tin complex Re2(CO)8(mu-SnPh2)2, 1 was obtained in 52% yield from the reaction of Re2(CO)8(mu-H)[mu-C(H)C(H)Bu] with Ph3SnH. Compound 1 contains two SnPh2 groups bridging a long Re-Re single bond, Re-Re = 3.1971(4) A [3.1902(4) A], Re-Sn = 2.7429(4) A [2.7445(4) A], and 2.7675(4) [2.7682(5) A]. A bis-Pd(PBut3) adduct of 1, Pd2Re2(CO)8(mu-SnPh2)2(PBut3)2, 2 was obtained from the reaction of 1 with Pd(PBut3)2. Compound 2 contains Pd(PBut3) groups bridging two of its four Re-Sn bonds. The Re-Re bond and the unbridged Re-Sn bonds in 2 are significantly longer than those in 1, 3.245(1) A and 2.8167(14) A, respectively. Fenske-Hall molecular orbital calculations on 1 and 2 have been performed to explain the metal-metal bonding in these unusual mixed-metal polynuclear metal complexes.     

Bond lengthening and through-bond interactions in p,p'-dibenzene and related molecules

The structure of p,p'-dibenzene (PDB) has been investigated by full geometry optimizations using the empirical force field (EFF) and MINDO/3 methods. While other structural parameters are in good agreement, the central bond length calculated by MINDO/3 (1.595 Å), as confirmed by an ab initio (STO-3G basis set) optimization (1.596 Å), is in striking contrast to the corresponding length calculated by EFF (1.543 Å). A detailed analysis of the electronic structure of PDB based on a quantitative perturbational molecular orbital treatment reveals that through-bond coupling of the four π systems is responsible for an elongation of the σ bond which mediates this interaction. Further studies using the EFF and MINDO/3 approaches demonstrate that extended C-C single bonds can arise even in structures with fewer than four π systems. The effect of substituents on the central bond length in PDB has been briefly investigated. (MINDO/3). A variety of other structures have been identified in which bond lengthening may result from through-bond coupling.     

Synthesis and characterization of molybdenum oxo complexes of two tripodal ligands: reactivity studies of a functional model for molybdenum oxotransferases

Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (L-OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L-O)]PF6. Similarly, the reaction of N-(2-mercaptobenzyl)-N,N-bis(2-pyridylmethyl)amine (L-SH) with MoO2(acac)2 leads to the formation of [MoO2(L-S)]+. The dioxo-molybdenum complex [MoO2(L-O)]+ reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV)O(L-O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L-O)]PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [(L-O)OMo(micro-O)MoO(L-O)](PF6)2. The crystal structures of [MoO2(L-O)]PF6 and the micro-oxo bridged dimer are presented.     

Total Synthesis of (±)-α-Acoradiene via Intramolecular Photoaddition and Reductive Cyclobutane Cleavage

(±)-α-Acoradiene (4) has been synthesized from 3-methoxy-2-cyclohexenone by a sequence of 8 steps. The key steps (Scheme 6) are the regio- and stereoselective photo[2+2]addition 7→6 and the reductive fragmentation 6→5 .