Nico J. R. van Eikema Hommes

Friedrich-Alexander-University of Erlangen-Nürnberg | FAU · Computer-Chemistry-Center

The famous aromaticity index NICS (Nucleus Independent Chemical Shift) was introduced 25 years ago. The authors use this anniversary for a short and incomplete personal retrospect.

The deprotection of chiral 1,2-bis(tosylamides) to their corresponding 1,2-diamines is mostly unsuccessful under standard conditions. In a new methodology, the use of Mg/MeOH with sufficient steric additions allows the facile synthesis of 1,2-diamines in 78-98% yields. These results are rationalized using density functional theory and the examinati...

Complexes of the Lewis base-free cations (MeBDI)Mg+ and (tBuBDI)Mg+ with Ph-X ligands (X= F, Cl, Br, I) have been studied (MeBDI = HC[C(Me)N-DIPP]2 and tBuBDI = HC[C(tBu)N-DIPP]2; DIPP = 2,6-diisopropylphenyl). For the smaller β-diketiminate ligand (MeBDI) only complexes with PhF could be isolated. Heavier Ph-X ligands could not compete with bondin...

Evolution has yielded biopolymers that are constructed from exactly four building blocks and are able to support Darwinian evolution. Synthetic biology aims to extend this alphabet, and we recently showed that 8-letter (hachimoji) DNA can support rule-based information encoding. One source of replicative error in non-natural DNA-like systems, howev...

Density functional theory and extrapolated CCSD(T) computations of several “anti‐Bredt” alkenes were carried to explore possible 1,2‐diyl “alkene” candidates with a triplet ground state. Ten candidates containing twisted double bonds at the bridgehead positions of bicyclic structures (1‐6) or adamantene (7‐10) derivatives were studied. Based on a c...

Density functional (B3LYP, B3PW91, X3LYP, BP86, PBEPBE, PW91PW91, and M06) and ab initio (MP2, MP4sdq, CCSD, and CCSD(T)) calculations with extended basis sets (6-311+G**, TZVP, LANL2DZ+p, and SDD+p, the latter including extra polarization and diffuse functions) indicate that HCN exchange on [Cu(HCN)4]+ proceeds via an associative interchange (Ia)...

The crystal structure of (LiCH 2 CH 2 CH 2 OMe) 4 [(3) 4 ] consists of a distorted (CH 2 ) 4 Li 4 cube, four parallel edges of which are spanned by CH 2 CH 2 OMe chains. The interatomic distances provide insights into the nature of alkyllithium‐ Lewis base (ethers, tertiary amines) interactions and into the structural basis of the differential reac...

1,2-Dilithioethane (I) is postulated to be formed together with dilithiomethane (VIII, main product) from methylene iodide and lithium 4, 4′-di-tert-butylbiphenyl in THF at T < -70°C. With Me3SnCl the tin derivatives of I, VIII and their C3 and C4 homologues are obtained.

1,2-Bis(halomagnesio)ethane 3 is generated from diiodomethane and lithium-4,4′-di-tert-butylbiphenyl in the presence of MgBr2.

C2Li4 is an acetylene and not an ethylene derivative, despite its stoichiometry. All the isomers correspond to minima on the potential energy surface of C2Li4. Ab initio calculations established the occurrence of Li, Li, and Li units, characteristic for per- and hyperlithiated molecules, and showed that structure 1 lies at the global energy minimum...

Despite having six highly electronegative F's, perfluorobenzene C(6)F(6) is as aromatic as benzene. Ab initio block-localized wave function (BLW) computations reveal that both C(6)F(6) and benzene have essentially the same extra cyclic resonance energies (ECREs). Localized molecular orbital (LMO)-nucleus-independent chemical shifts (NICS) grids dem...

Polycryst. bicyclic diironcryptates with different mobile guest cations were synthesized and characterized by XRD anal., IR spectroscopy, FAB-mass spectroscopy, elemental anal., elec. cond. spectroscopy and ion exchange expts. Strong indication that the guest cations exhibit a long-range mobility and that their mobility is governed by their size re...

Solutions of LiClO(4) in solvent mixtures consisting of dimethylsulfoxide (DMSO) and water, or DMSO and gamma-butyrolactone, were studied by (7)Li NMR spectroscopy (for complexation by cryptands in gamma-butyrolactone as a solvent, see: E. Pasgreta, R. Puchta, M. Galle, N. J. R. van Eikema Hommes, A. Zahl, R. van Eldik, J. Incl. Phen., 2007, 58, 81...

Seven-coordinate manganese(II) complexes were studied with regard to their acid−base properties, water-exchange rate constants, and corresponding activation parameters (ΔH⧧, ΔS⧧, and ΔV⧧). Three of the studied complexes are proven superoxide dismutase (SOD) mimetics. In addition, the X-ray crystal structure of a new Mn(II) seven-coordinate complex...

Kinetic studies on Li+ exchange between the cryptands C222 and C221, and γ-butyrolactone as solvent were performed as a function of ligand-to-metal ratio, temperature and pressure using 7Li NMR. The thermal rate and activation parameters are: C222: k 298=(3.3 ± 0.8)×104M−1s−1, ΔH #=35 ± 1kJmol−1 and ΔS #= −41 ± 3JK−1mol−1; C221: k 298=105 ± 32M−1s−...

DFT-calculations (RB3LYP/LANL2DZp) show that the migration of a proton inside [1.1.1]- and [2.2.2]-cryptand from one nitrogen atom to the other follows different paths. While the proton in [H subset of 1.1.1]-cryptand moves via an ether oxygen atom (activation energy: 19.2 kcal/mol), the proton in [H subset of 2.2.2]-cryptand moves directly from on...

The enantiomerisation pathway for {[Pt(thiourea)4]}F+ [a model for the C-4-symmetric [Pt(SU)(4)]SiF6 (SU = thiourea) complex] and derivatives is explored by density functional theory (B3LYP/LANL2DZp) and the activation barrier for the one-step process from C-4 to C-4' via a C-4 transition state is computed. The substitution of Pt2+ by Pd2+ and Ni2+...

DFT-calculations (RB3LYP/LANL2DZp) show that the migration of a proton inside [1.1.1]- and [2.2.2]-cryptand from one nitrogen atom to the other follows different paths. While the proton in [H⊂1.1.1]-cryptand moves via an ether oxygen atom (activation energy: 19.2 kcal/mol), the proton in [H⊂2.2.2]-cryptand moves directly from one nitrogenatom to th...

Based on DFT calculations (RB3LYP/LANL2DZp), the unexpected single-line 1H NMR spectrum of Zn(II)(nta), nta = 2,2',2''-nitrilotriacetate, can be ascribed to a non-dissociative enantiomerization process (deltadeltadelta<=>lambdalambdalambda) from C3viaC3v to C3 symmetry. The energy barrier is rather low and depends to a lesser extent on the nature o...

Structures of [M subset of 2.2.2](n+) obtained with MNDO, AM1, PM3, PM3/SPASS, and PM5, are evaluated against X-ray and DFT (B3LYP/LANL2DZp) geometries. DFT and X-ray structures agree well, followed by PM3/SPASS. The ion selectivity calculated with DFT and PM3/SPASS for a simple model reaction, agrees satisfactorily with the available complex-forma...

The effect of different N-N spectator ligands on the reactivity of platinum(II) complexes was investigated by studying the water lability of [Pt(diaminocyclohexane)(H2O)2]2+ (Pt(dach)), [Pt(ethylenediamine)(H2O)2]2+ (Pt(en)), [Pt(aminomethylpyridine)(H2O)2]2+ (Pt(amp)), and [Pt(N,N'-bipyridine)(H2O)2]2+ (Pt(bpy)). Some of the selected N-N chelates...

DFT-calculations (RB3LYP/LANL2DZp) show that the migration of a proton inside [1.1.1]- and [2.2.2]-cryptand from one nitrogen atom to the other follows different paths. While the proton in [H⊂1.1.1]-cryptand moves via an ether oxygen atom (activation energy: 19.2 kcal/mol), the proton in [H⊂2.2.2]-cryptand moves directly from one nitrogenatom to th...

The protonation of thiourea was reinvestigated in aqueous and non-aqueous media using potentiometric, UV-vis, NMR, MS spectroscopy, as well as DFT calculations. In aqueous medium, no evidence for protonation could be found in the pH range 0 to 7, in agreement with typical pKa values (acid dissociation constants of protonated thiourea) quoted in the...

When normal is a surprise: Studies of a ligand-substitution reaction of a PtII complex (see picture; apa: 2,6-bis(aminomethyl) pyridine) in water, methanol, and the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide reveal that the ionic liquid behaves "normally", that is, as any other solvent. In the ionic liquid, changes i...

The kinetics of the formation of the active species cis-[PtII(PPh3)2Cl(SnCl3)] and cis-[PtII(PPh3)2(SnCl3)2] from the hydroformylation catalyst precursor cis-[PtII(PPh3)2Cl2] in the presence of SnCl2, was studied in two different imidazolium-based ionic liquids. A large range of different chlorostannate melts consisting of 1-butyl-3-methyl-imidazol...

Linear regression formulae are given for converting 1H and 13C magnetic shielding constants calculated at common ab initio and density functional theory levels of calculation into chemical shifts relative to tetramethylsilane. Accuracies of roughly +/-2.2 ppm (13C) and +/-0.15 ppm (1H) or better are found for the training set for most levels. The h...

Compared with Katsuki's or Jacobsen's catalysts (R,R,R,R)-1 or (R,R)-2, the phenomenon of reversed asym. induction in the course of the epoxidn. of unfunctionalised olefins in the presence of (salen)manganese complex (S,S)-3 (I) is indirectly explained by means of quantum chem. calcns., as well as by 1H NMR spectra of salen ligand and diamagnetic l...

The ligand-exchange mechanism of solvated Be2+ cations has been studied by means of DFT calculations (RB3LYP/6-311+G**). Ligand exchange around [BeL4]2+, where L=H2O, NH3, CO2, formaldehyde (H2CO), HCN, N2, and CO, was found to follow an associative interchange (Ia) process in all cases. The size of the activation barrier is almost independent of t...

The first experimental example of a [4n]annulene derivative with one Mobius twist, 1, was synthesized recently [Ajami, D.; Oeckler, O.; Simon, A.; Herges, R. Nature 2003, 426, 819] and was purported to possess aromatic character. However, critical analysis of the published crystallographic data indicates that the Mobius [16]annulene core of 1 shows...

The ligand exchange mechanism of solvated lithium cations has been studied using DFT calculations (RB3LYP/6-311+G**). The water exchange mechanism on [Li(H(2)O)(4)](+) was found to be limiting associative (A) involving a five-coordinate intermediate, whereas ammonia exchange on [Li(NH(3))(4)](+) was found to follow an associative interchange (I(a))...

Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [4]phenylene (D3h[4]phenylene) were studied using laser-excited Shpolskii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31...

The nature of the tetrahedral H42+ stationary point (minimum or triply degenerate saddle) depends remarkably upon the theoretical level employed. Harmonic vibrational analyses with, e.g., the 6-31G** (and 6-31 + +G**) and Dunning's [4s2p1d;2s1p] [D95(d,p)] basis sets using the standard p exponent suggest (erroneously) that the Td geometry is a mini...

High-level ab initio calculations {QCISD(T)/6-311 +G**//MP2(fu)/6-31 +G**, with corrections for higher polarization [evaluated at MP2/6-311 +G(3df,2p)] and ΔZPE//MP2(fu)/6-31 +G**, i.e., comparable to Gaussian-2 theory} indicate concerted mechanisms for double- and triple-hydrogen exchange reactions in HF and HCl dimers and trimers, in mixed dimers...

The cover picture shows the X‐ray structure of a six‐membered iron wheel. In order to support its existence in solution and to gain deeper insights into the possible flexibility of its scaffold, we prepared an indium analogue. Temperature‐dependent ¹ H NMR solution spectra of the indium wheel (depicted in the middle) revealed intramolecular dynamic...

In the reaction of the N-substituted diethanolamines (H(2)L(1-3)) (1-3) with calcium hydride followed by addition of iron(III) or indium(III) chloride, the iron wheels [Fe(6)Cl(6)(L(1))(6)] (4) and [Fe(6)Cl(6)(L(2))(6)] (6) or indium wheels [In(6)Cl(6)(L(1))(6)] (5), [In(6)Cl(6)(L(2))(6)] (8) and [In(6)Cl(6)(L(3))(6)] (9) were formed in excellent y...

Surprisingly, doubly functionalised (2S,3S)-diazidobutane-1,4-diol under modified Boyer conditions reacted with only 1 equiv of benzaldehyde yielding a mono oxazoline, whereas quantum chemical studies favour the formation of the C2-symmetric bioxazoline. In addition, the oxazoline formation was indirectly confirmed via detailed NMR studies and X-ra...

Vibrationally resolved fluorescence spectra of four angular [N]phenylenes were recorded with laser excited Shpol’skii spectroscopy (LESS) in an n-octane matrix at 10 K. In general, the same vibrational frequencies were observed in the fluorescence excitation and emission spectra, indicating that the geometries of ground and electronically excited s...

It has been found by serendipity during the attempted synthesis of the potential tris-bidentate ligand 7 that this compound undergoes multiple ring-closure reactions to form the heterodamantane derivative 12. This reaction involves a domino aldol addition/hemiketal formation/hemiketal formation/epimerization sequence. Compound 12 was studied intens...

[structure: see text] In contrast to the 1,6-X-[10]annulenes (X = CH(2), O, NH) with delocalized forms (c), their X = PH and S counterparts favor the bisnorcaradiene structures (b). Forms b and c are close in energy with X = SiH(2) and SiMe(2). The computed nucleus independent chemical shifts (NICS), show both annulenes (c) and cyclic polyenes (a)...

[structure: see text] Analysis of the basic pi-aromatic (benzene) and antiaromatic (cyclobutadiene) systems by dissected nucleus-independent chemical shifts (NICS) shows the contrasting diatropic and paratropic effects, but also reveals subtleties and unexpected details.

Analysis of the basic π-aromatic (benzene) and antiaromatic (cyclobutadiene) systems by dissected nucleus-independent chemical shifts (NICS) shows the contrasting diatropic and paratropic effects, but also reveals subtleties and unexpected details.

High level ab initio and density functional calculations, extrapolated to QCISD(T)/6-311+G(3df,2p)//MP2/6-31+G**+ZPE, reveal that cyclic ion pairs can form in the hydrogen bonded complexes of haloboric acids BHnX3-n–HX, X=F, Cl, with Lewis bases HX, H2O, CH3OH, and NH3, even in isolation (e.g., in the gas phase). The intrinsic acidities (deprotonat...

Semiempirical PM3 computations are reported for the {2}-gallium cryptand and {2}-gallium cryptates with three 2,6-bis(acetylaceto)pyridine ligands. Optimized sparkles are employed for the description of metal ion guests for which no PM3 parameters are available. Calculated structures agree well with available X-ray structures of the corresponding {...

Reactions of Cp2Ti(CO)2 (3) with two equivalents of α,β-unsaturated ketones 4 yield the novel titana-2,9-dioxacyclonona-3,7-dienes 5. Cross-coupling of 3 with two different ketones 4 and 6to give 7 can be achieved under certain reaction conditions. Hydrolysis of 5 or 7 may generate diketones 9, cyclopentanols 10/11, or cyclopentenes 12/13, dependin...

Two pyrrole rings participate in the aromatic structure of porphyrin. Hence, a 22 π-electron description is better than the usual [18]annulene representation. The dianion and the metal complex system favor different electronic structures.

Zwei Pyrrolringe sind Bestandteil der aromatischen Struktur von Porphyrin. Daher sollte es eher als 22π-Elektronensystem (siehe rechts) denn als [18]Annulen beschrieben werden. Dagegen bevorzugen sowohl das Dianion als auch die Metallkomplexe grundlegend andere elektronische Strukturen.

Die konkave innere Oberfläche von C 60 ist so inert gegenüber der Bildung kovalenter Bindungen, daß sogar atomarer Stickstoff im Quartett‐Grundzustand als eingeschlossener Gast stabil ist (siehe rechts). Computerchemische und ESR‐Untersuchungen. liefern eine Erklärung für dieses beispiellose Verhalten. magnified image

Do the chemical properties of the surface of a carbon sheet depend on its shape? This question addresses a criterion for chemical behaviour that has hardly been investigated previously. The current neglect of this question may be due to the fact that suitable model systems with easily distinguishable graphitic surfaces were essentially unknown unti...

The concave inner face of C60 is so inert with respect to the formation of covalent bonds, that even atomic nitrogen in the quartet ground state is stable as an encapsulated guest (shown on the right). Semiempirical calculations and ESR investigations offer an explanation for this unprecedented behavior.

The monomer, dimer, and tetramer of methyllithium, (CH3Li)n (n = 1, 2, 4), have been studied with use of density-functional (DFT) and conventional ab initio theory. The energy gain AE associated with the formation of (CH3-Li)n from n Li• and n CH3• radicals is -45.5, -132.7, and -308.6 kcal/mol for n - 1, 2, and 4 using nonlocal density-functionals...

[5]Pericyclynes were investigated at high ab initio and density functional levels. On the basis of the geometric, energetic, and magnetic criteria of aromaticity, [5]pericyclynes are not homoaromatic despite their intriguing structure. The strain energy of [5]pericyclynes is negligible.

High-level ab initio calculations (MP4sdtq/6-311+G**//MP2/6-31G*) predict classical structures for monomeric lithioborane and the dimethyl, diamino, and difluoro derivatives. A structure with the lithium cation bridging one boron oxygen bond is computed as the most stable structure for dihydroxylithioborane. For this compound, an "inverted" structu...

High level ab initio calculations (MP2(fc)/6-31+ G*/MP2(fc)6-31G*Δ+ZPE/6-31IG* show that the reaction of aromatic compounds with methyllithium is not an electrophilic substitution, but a hydrogen transfer along an almost linear path, with the (coordinatively highly unsaturated) “active” lithium cation bridging the methyl carbanion and the carbon at...

Ab initiocalculations (MP4/6-31+G*//6-31+G*+ΔZPE) have been performed on the ring-opening reaction of ethylene oxide by monomeric and dimeric lithium hydride and by dimeric methyllithium, both with retention and with inversion of configuration at the carbon being attacked. Several highly ionic transition structures were located. The large preferenc...

The H atoms and not the Si atom of the SiH3 groups coordinate to two of the eight Na atoms in [Na8(OC2H4OC2H4OCH3)6-(SiH3)2]. Shown here is the novel Na8O6 polyhedron containing the two SiH3 groups. The surfaces of the Na8 cube are capped by oxygen atoms. Ab initio calculations on a suitable model showed that the inverted coordination mode is indee...

The metalation of toluene (PhCH3) with a 1:1 mixture of n-BuLi/MO(t)Bu (M = K,Rb) at ambient temperature affords orange-red powders of benzylpotassium or benzylrubidium. On addition of N,N,N,N'',N''-pentamethyldiethylenetriamine (PMDTA) the precipitates dissolve to give burgundy-red solutions, from which needles of [PhCH2K.PMDTA.0.5PhCH3]n (1) or [...

Die H-Atome und nicht das Si-Atom der SiH3Gruppen- koordinieren in [Na8(OC2H4OC2H4OCH3)6(SiH3)2] an zwei der acht Na-Atome. Rechts ist das neuartige Na8(O6-Polyeder, ein Na8-Würfel mit Sauerstoff-überdachten Flächen, mit den beiden SiH3-Gruppen gezeigt. Die energetische Bevorzugung der invertierten Koordination konnte durch ab-initio-Rechungen an e...

Energy differences between five isomeric monolithiated 4-picolines 6a (eta3 at Calpha/C4/C3), 6b (eta5 at Nl/C2/C3/C6/C5), 6c (eta2 at Calpha/C4), 6da (N1-lithiated), and 6e (eta3 at C3/C4/C5) were calculated by ab initio (MP2/6-31+G*//6-31G*) and semiempirical (MNDO) methods. With this basis set and inclusion of the ZPE correction, 6a-c and 6e tur...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Keine Ethylen‐, sondern Acetylenderivate sind alle C 2 Li 4 ‐Isomere, die Minima auf der Energiehyperfläche entsprechen, obwohl die Stöchiometrie das nicht erwarten läß Quantenchemische ab‐inito‐Rechungen ergaben das Vorliegen von Li ‐, Li ‐ und Li ‐ Einheiten wie sie für per‐ und hyperlithiierte Moleküle charakteristisch sind, und als globales Min...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Not the complexation of the ground state but rather of the transition state explains the directing and activating effect of electronegative ortho substituents in the lithiation of aromatic compounds. Ab initio calculations show that the ground state of a C 6 H 5 FLiH complex for para metalation (complexation by the benzene ring) is energetically m...

Nicht die Komplexierung des Grund‐, sondern die des Übergangszustandes erklärt die dirigierende und aktivierende Wirkung elektronegativer ortho ‐Substituenten bei der Lithiierung aromatischer Verbindungen. So ergeben ab‐initio‐Rechnungen, daß der Grundzustand eines C 6 H 5 F‐LiH‐Komplexes für die para ‐Metallierung (Komplexierung durch den Benzolri...

NMR studies and MNDO calculations show that the title compound exists as two monomeric species in solution with two most stable structures (one of the structures is shown here). As expected, N2 and N3 are coordinated to the Li atom: however, the Li-N1 interaction is quite weak.

NMR‐Studien und MNDO‐Rechnungen zeigen , daß die Titelverbindung in Lösung in Form zweier monomerer Spezies vorliegt bzw. zwei stabilste Strukturen bildet (eine der Strukturen zeigt das Bild rechts), in denen N2 und N3 erwartungsgemäß an das Li‐Atom koordiniert sind, N1 aber nur in schwacher Wechselwirkung mit diesem steht. magnified image

Tetrahedral angles are the exception rather than the rule in compounds containing maingroup elements and organic groups. The deviations may be substantial as is demonstrated by the opening of the CCB angle in triethylborane to almost 120° (structure shown right), which can be explained by the hyperconjugative interaction of boron's empty p orbital...

Eher die Ausnahme als die Regel sind ideale Tetraederwinkel in Organoelementverbindungen. Die Abweichungen können beträchtlich sein, wie die Aufweitung des C-C-B-Winkels in Triethylboran auf fast 120° (Strukturbild rechts) zeigt. Dies läßt sich mit einer hyperkonjugativen Wechselwirkung des leeren Bor-p-Orbitals mit den bindenden Orbitalen der α-C-...

Ziegler's disproportionation reaction of methyllithium to give dilithiomethane and methane upon heating to 225°C is predicted by ab initio theory (MP2/6-31+G*//6-31G*) to proceed endothermically through a polar hydrogen-transfer mechanism within a tetrameric methyllithium aggregate, (CH3Li)4 → CH2Li2·(Li/CH3)2 + CH4. A free energy of reaction of +1...

The X-ray structure of the title compound (1-TMEDA) shows that the essentially symmetrical allyl anion moiety is perturbed by complexation with TMEDA in a twisted conformation. The NMR-observed symmetrization of both the allyl end carbons and all the TMEDA methyl groups at higher temperatures is best modeled by molecular orbital calculations when t...

The ab initio structures calculated for the LiCs series of allyl alkali metal compounds prefer symmetrically bridged geometries. Bonding is mainly electrostatic; the natural charges on the metals range from 0.910 (Li) to 0.999 (Cs). Dimerization and solvation, which were studied for allyllithium, result in longer bonds to the metal. Rotational bar...

Dilithium diphenylmethanediide, Ph2CLi2, prepared by reaction of dichlorodiphenylmethane with lithium p,p′-di-tert-butylbiphenyl, reacts with organic halides and carbonyl compounds to give lithium Chlorodiphenylmethanide, Ph2CLiCl, as a major product and is assumed to exist in two different states of aggregation.

Several methods of preparing the title compound (III) are investigated.

The preparation of the title compound (1) by three different routes is described. The compound was found to be remarkably unreactive towards electrophiles.

The dilithium compound (III) mentioned in the title is obtained by lithiation of the disilyldichloromethane (I) with 4,4'-di-tert-butyldiphenyllithium (II) or with a suspension of lithium in THF in the apparatus of Kundig and Perret.

Generation of the thermally unstable 1,2-dilithioethane 1, which had eluded earlier synthetic attempts, has now been carried out under special conditions. Condensation of lithium vapor on a glass formed from ethylene and dimethyl ether at — 196°C yielded highly active lithium, which, upon melting of the glass, reacted with ethylene to afford 1. Com...

Le dilithio-1,2 ethane est obtenu par condensation de vapeur de lithium sur un verre d'ethylene et d'ether methylique a −196° suivi de la fusion du verre dans l'appareil decrit par Kundig et Perret. Il est piege par stannylation et par carboxylation puis methylation

The main product of the reduction of (I) by (II) is the title compound (III).

X-ray analysis indicates the crystals of the title compound to consist of a distorted (CH2)4Li4 cube, four parallel edges of which are spanned by CH2CH2OMe chains (space group C2/c, Z=4).

Room temperature phosphorescence in liquid solutions (RTPL) is applied as a detection method in the chromatographic analysis of technical mixtures of polychloronaphthalenes (PCNs) and polychlorobiphenyls (PCBs). The identification of PCBs is strongly facilitated by combining UV detection and detection based on sensitized RTPL of biacetyl, since the...

It is shown that sensitized room-temperature phosphorescence in liquid solutions can be successfully applied as a detection method in continuous flow and chromatographic systems. The limits of detection for a series of halogenated naphthalenes and biphenyls obtained by plug injection are roughly the same as those in batch experiments — in the subna...

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