Koordinationschemische Untersuchungen an Zinkdialkylen. XVI. Darstellung und Untersuchung von Dinorbornylzink-Verbindungen

Investigations on the Coordination Chemistry of Zinc Dialkyls. XVI. Synthesis and Investigation of Dinorbornyl Zinc Compounds Bis(1-norbornyl)-, bis(2-norbornyl)-, and bis(7-norbornyl)zinc were synthesized from zink chloride and the corresponding Grignard compounds or norbornyl lithium compounds, respectively. The properties of these compounds differ remarkably. A detailed characterization took place by the mass, IR and ¹³C-NMR spectra and by investigation of the thermal decomposition and complex formation reactions. For comparison the bis(7-norbornenyl)zinc was prepared and characterized.     

Darstellung und Eigenschaften von Norbornylquecksilberverbindungen

Preparation and Properties of Norbornyl Mercury Compounds Bis(1-norbornyl) and bis(2-norbornyl)mercury, 1- und 2-norbornylmercury chloride and 1-norbornylmercury i-butyl were synthesized and characterized by ¹³C-N.M.R. investigations and in case of bis(1-norbornyl) mercury also by the I.R. and mass spectrum. The ¹J(¹⁹⁹Hg? ¹³C) coupling constants of the 1-norbornyl compounds demonstrate the trans-influence of the norbornyl anion.     

Etude des possibilites de dosage du lithium par activation au moyen de protons et de deutons de moyenne energie

The determination of lithium by measuring⁷Be, produced by proton or deuteron activation, has been studied. The extent of interference from boron or beryllium, which also form⁷Be, was measured. The calculated sensitivity limits when activating for one hour with 10μA beams of 14 MeV protons or 25 MeV deuterons are, for lithium, 1·10⁻¹ and 2.5·10⁻² ppm and for boron, 2·10⁻¹ and 1·10⁻¹ ppm, respectively.      

Use of a Carbon Paste Electrode Modified with Spinel‐Type Manganese Oxide as a Potentiometric Sensor for Lithium Ions in Flow Injection Analysis

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel‐type manganese oxide (lambda‐MnO₂), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li⁺ against other alkali and alkaline‐earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6×10^?5–1.0×10^?2 mol L^?1 with a slope 78.9±0.3 mV dec^?1 over a wide pH range 7–10 (Tris buffer), without interference of other alkali and alkaline‐earth metals. For a flow rate of 5.0 mL min^?1 and a injection sample volume of 408.6 μL, the relative standard deviation for repeated injections of a 5.0×10^?4 mol L^?1 lithium ions was 0.3%.     

Darstellung und Eigenschaften von 1-Norbornylkupfer

Preparation and Properties of 1-Norbornyl Copper 1-Norbornyl copper was synthesized from copper(II) acetylacetonate and 1-norbornyl lithium. The compound shows an unexpected stability and decomposes only at ca. 80°C with precipitation of copper and formation of norbornyl radicals which were proved by spin-trap experiments. A further characterization was performed by the IR and ¹³C-NMR spectra.     

The Acetolysis of exo- and endo-5,6-Dimethylidene-2-Norbornyl p-Bromobenzenesulfonates and of their Optically Active and Deuterium-Labelled Derivatives

The buffered (AcOK) acetolyses of exo, (11) and endo-5, 6-dimethylidene-2-norbornyl brosylate (12) yielded exo5, 6-dimethylidene-2-norbornyl (16) and (3-methylidene-2-nortricyclyl)methyl acetates (18) . Endo-5, 6-dimethylidene-2-norbornyl (17) and 2-methylidene-3-tricyclo [3.2.1.0^3,6]octyl acetates (20) could not be detected. The titrimetric rate constants of the acetolysis of 11 (k_t(exo)=4.49 ± 0.02) · 10^?5 s^?1 at 25°, ΔH^≠=23.6 ±0.7 kcal mol^?1, ΔS^≠=0.7 ±2 calmol^?1 K^?1 and 12 (k_t(endo)=1.9 ±0.08) · 10^?9 s^?1 at 25°, ΔH^≠=27 ±1 kcal mol^?1, ΔS^≠=-8 ±2.5 calmol^?1 K^?1) were measured and compared with the polarimetric rate constants (k_α/k_(exo)=6.8 at 25°,(k_α/k_(exo)=1.0 at 121°) of the buffered acetolyses of the optically active brosylates (+)- 11 and (+)- 12 . Neither a common-ion (KOBs) nor a special ion effect (LiClO₄) on k_t(endo) could be detected, although external return might well intervene as some exo-5,6-dimethylidene-2-norbornyl tosylate (21) was formed upon solvolysis in the presence of KOTs. Acetolysis of (+)- 11 yielded completely racemized products, whereas (+)- 12 led to incomplete racemization. The buffered acetolysis of exo-(3exo-D)-5,6-dimethylidene-2-norbornyl brosylate (24) furnished (3exo-D)-( 26 :37.5%), exo-(7syn-D)-5,6-dimethylidene-2-norbornyl brosylate (27 : 37.5%) and [(5anti-D)-3-methylidene-2-nortricyclyl]methyl acetates (28 : 25 %). The acetolysis of endo-(2exo-D)-5,6-dimethylidene-2-norbornyl brosylate (25) yielded (2endo-D)-( 29 : 54%), exo-(1-D)-5,6-dimethylidene-2-norbornyl ( 30 : 36%) and [(6-D)-3-methylidene-2-nortricyclyl]methyl acetates ( 31 : 10%). Product analysis and deuterium label distribution was established by a combination of GC., ¹H-NMR., ²H-{¹H}-NMR. and MS. techniques. The results are rationalized by invoking anchimerically assisted ionization of the exo-brosylate 11 to symmetrical ion-pairs (cyclopropylcarbinyl cation intermediates) which undergo internal (and probably also external) return. Acetolysis of the endo-brosylate 12 is not anchimerically assisted and leads initially to non-symmetrical ion pairs. These evolve to symmetrical ion pair intermediates or, to a minor extent, are intercepted by solvent.     

Verbrückte und unverbrückte norbornyl-kationen in der gasphase. Berechnungen zur stabilität isomerer norbornyl-kationen mit hilfe quantenmechanischer verfahren

The geometry and the relative stability of bicyclic compounds 1–20 have been calculated by standard quantum mechanics methods.MINDO/3 yields the following stability order of isomeric norbornyl cations (relative energies in $\text{kcal}\text{mole}$): 1-norbornyl cation 9 (0.0); 1.7 σ-bridged cation 6 (0.7); 7-norbornyl cation (nonplanar) 7 (1.1); 2-norbornyl cation (classical) 2 (4.2); 7-norbornyl cation (planar) 8 (4.3); 2-norbornyl cation (bridged) 1 (6.1). The stability of the same ions calculated by ab initio methods (STO-3G, MINDO/3-geometry) leads to an order more nearly consistent with experimental results: 2-norbornyl cation (classical) 2 (0.0); 2-norbornyl cation (bridged) 1 (5.9); 7-norbornyl cation (planar) 8 (11.1); 1-norbornyl cation 9 (14.6); 7-norbornyl cation (nonplanar) 7 (21.2). For the secondary 7-norbornyl cation, MINDO/3 gives a pyramidal configuration, 3.2 $\text{kcal}\text{mole}$ more stable than the planar form. In contrast, the ab initio results (complete optimization of all geometrical parameters) indicate the planar cation to be the most stable form. The bridged structure of 2-norbornyl cation 1 is calculated (STO-3G, partly optimized) to be 4.3 $\text{kcal}\text{mole}$ less stable than the classical counterpart, 2. For the lower homologues 12 and 13 (STO-3G, complete geometry optimization), this difference is 6.4 $\text{kcal}\text{mole}$. However, more extended basis sets should favour the bridged structures. The hydrogen bridged norbornyl cations 3, 4, and 5 have been calculated (STO-3G, partly optimized) to be 14.4, 23.6 and 29.9 $\text{kcal}\text{mole}$ less stable than 2. The stability differences between the corresponding tertiary bicyclic ions 10 vs 11, and 14 vs 15 are calculated (ab initio) to be 15.3 and 19.0 kcal/mole, respectively, in favour of classical structures. The influence of methyl substitution at positions C₁ and C₆ (exo) on bridged and unbridged structure of 2-norbornyl cation is calculated. Pyramidal secondary and tertiary 2-norbornyl cations 19 (a; R=H, b; R=CH₃) and 20 (a; R=H, b; r=CH₃) have been used to model the electrical effects in the solvolysis transition states of epimeric 2-norbornyl esters. Due to more efficient hyperconjugation the pyramidal exo cation is stabilized more than the endo cation by 5.2 $\text{kcal}\text{mole}$ for the secondary series and 3.5 $\text{kcal}\text{mole}$ for the tertiary series. Bonding of endo cation 20 with a nucleophile should be stronger than bonding of exo cation 19 due to more efficient HOMO-LUMO interaction.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XLII. Untersuchungen über Norbornylverbindungen des Titans,Zirconiums und Hafniums

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XLII. Investigations on Norbornyl Compounds of Titanium, Zirconium, and Hafnium It is reported about ¹³C-NMR, IR, and mass spectroscopic measurements of (1-Nor)₄M derivatives of Ti, Zr, and Hf and unsuccessful efforts for synthesis of 1-norbornyl titanium halides Furthermore, (2-Nor)₄Ti and (2-Nor)₄Zr were synthesized. These compounds are remarkably less stable than the corresponding 1-norbornyl derivatives and appear to be exo/endo isomer mixtures. At thermolyses of (2-Nor)₄Ti stable (2-Nor)₂Ti is formed. The stability of (7-Nor)₄Ti is comparable with that of (2-Nor)₄Ti.     

Polar effects in the solvolysis of 6-exo-substituted endo-2-norbornyl p-toluenesulfonates

The solvolysis rates of endo-2-norbornyl p-toluenesulfonates $\text{1}$ are affected far less by 6-exo-substituents than are the rates of the corresponding exo-2-norbornyl p-toluenesulfonates $\text{2}$¹.     

Determination of boron and lithium in diverse biological matrices using neutron activation-mass spectrometry (NA-MS)

Summary Essential features of the neutron activation-mass Spectrometry (NA-MS) technique are described. Applicability of this technique for the simultaneous determination of boron and lithium is demonstrated for a diverse group of biomaterials. NA-MS is a nondestructive analytical technique, and dynamic in nature since its coverage extends to a broad range of concentration levels. Contamination after the irradiation step, extraneous by natural lithium or boron is inconsequential, since only the activation products are the analyted assayed. Coupling the nuclear activation phenomenon which generates ⁴He and ³He (from ¹⁰B and ⁶Li, respectively), with the high precision potential of mass spectrometry forms the bases of this technique. Under ideal conditions the detection limit is extendable to pg g^–1 concentration ranges and therefore, it is extremely well suited to investigate the natural concentration levels of boron and lithium in biomaterials. The potential of this method for the determination of lithium in biomedical trace element research is of special significance since determination of sub-ppb levels of lithium by other analytical techniques faces serious analytical difficulties mainly due to contamination control and in some cases to insufficiently low detection limits.     

Inductive and Polarizability Effects of an Exocyclic Diene-Iron Tricarbonyl Group. The acetolyses of exo- and endo-irontricarbonyl complexes of 5,6-dimethylidene-2-exo-norbornyl and 2,3-dimethylidene-7-anti-norbornyl parabromobenzenesulfonates

The exo- and endo-irontricarbonyl complexes of 5,6-dimethylidene-2-exo-norbornyl alcohols 10x, 10n , p-bromobenzenesulfonates 11x, 11n , acetate 12x and of the 2,3-dimethylidene-7-anti-norbornyl alcohols 17x, 17n , p-bromobenzenesulfonates 19x, 19n and acetates 20x, 20n have been prepared. The S_N1 buffered acetolyses of 11x, 19x and 19n gave 12x, 20x and 20n , respectively (retention of configuration). The first-order rate constants of the acetolyses have been evaluated and compared with those of the acetolyses of the uncomplexed 5,6-dimethylidene-2-exo-norbornyl ( 14 ) and 2,3-dimethylidene-7-anti-norbornyl p-bromobenzenesulfonates ( 18 ). A rate retardation effect of ca. 1.5 · 10⁵ was measured for 11x → 12x (65°) compared with the acetolysis of 14 . The retardation effect is larger (> 5 · 10⁷) with 11n . Contrastingly, the acetolysis 19x → 20x was slightly accelerated with respect to that of the uncomplexed p-bromobenzenesulfonate 18 . An unsignificant rate-retardation effect was measured for the acetolysis 19n → 20n . The results are interpreted in terms of competitive inductive destabilization and charge-induced dipole stabilizing interaction by the exocyclic diene-iron tricarbonyl fragment. PMO. arguments give a rationale for the difference in polarizability between the diene-Fe(CO)₃ group in 19 and that in the endo-7-norbornadienyl-iron tricarbonyl system.     

The Boron and Lithium Content of South African Coals and Coal Ashes

Abstract

Boron and lithium were determined in over a hundred coals and power station ashes by inductively coupled plasma atomic emission spectroscopy. The levels of boron in coals and fly ashes range from 15 to 83 μg.g^?1 and from 23 to 600 μg.g^?1, respectively, while lithium occurred at levels of between 45 and 81μg.g^?1 in coals and 77 and 359μg.g^?1 in fly ashes. Both elements were found to vary considerably between different coals and ashes produced. In most cases the boron concentration was found to increase systematically between the first and last precipitators where smaller particle size fractions are collected. The availability of boron from the leaching of fly ashes by water was investigated. Leachabilities were found to vary for ashes produced at different power stations.     

Ionic Covalent Organic Frameworks with Spiroborate Linkage

A novel type of ionic covalent organic framework (ICOF), which contains sp³ hybridized boron anionic centers and tunable countercations, was constructed by formation of spiroborate linkages. These ICOFs exhibit high BET surface areas up to 1259 m² g^?1 and adsorb a significant amount of H₂ (up to 3.11 wt %, 77 K, 1 bar) and CH₄ (up to 4.62 wt %, 273 K, 1 bar). Importantly, the materials show good thermal stabilities and excellent resistance to hydrolysis, remaining nearly intact when immersed in water or basic solution for two days. The presence of permanently immobilized ion centers in ICOFs enables the transportation of lithium ions with room‐temperature lithium‐ion conductivity of 3.05×10^?5 S cm^?1 and an average Li⁺ transference number value of 0.80±0.02. Our approach thus provides a convenient route to highly stable COFs with ionic linkages, which can potentially serve as absorbents for alternative energy sources such as H₂, CH₄, and also as solid lithium electrolytes/separators for the next‐generation lithium batteries.     

Speciation and analysis of corrosion products in the primary coolant of pressurized water reactors

The procedure involves separate sampling and determination of the insoluble, cationic and anionic species of corrosion products (Fe, Ni, Cr, Mn, Co, Zn, Cu) in the primary coolant of pressurized water reactors (PWRs) with concentrations in the range 0–2000 mg l^?1 boron and 0–5 mg l^?1 lithium. Samples of coolant (0.2–1 l) are passed through packs consisting of one 0.45-μm filter paper, one cation-exchange membrane (Whatman SA-2) and one anion-exchange membrane (Whatman SB-2). The membranes are examined by wavelength-dispersive x-ray spectrometry. Selection of the ion-exchange membranes and the influence of the boron and lithium concentrations (and pH) on retention of soluble species are discussed. With sample volumes of 0.5 l, the detection limits are between 0.05 and 0.3 μg l^?1 for undissolved species and from 0.03 to 0.14 μg l^?1 for ions. Data collected during a PWR shutdown procedure are summarized.     

Lithium-bis(silyl)amide und Tris(silyl)amine Synthese und Kristallstrukturen

Lithium Bis(silyl)amides and Tris(silyl)amines Synthesis and Crystal Structures Lithiated di-tert-butylfluorosilylamine reacts with difluorosilanes by substitution ( 1, 2 ). The siloxy-( 3, 4 ) and tert-butyloxy-( 5 )-silylamines are formed in reaction of 1 and 2 with LiOR (R = SiMe₃, CMe₃). The lithium derivatives of 3 and 4 are dimers forming an (LiFSiN)₂-eight-membered ring ( 6, 7a ). Using 12 crown-4 the amide and the coordinated lithium are forming free ions ( 7 c ). The lithium derivative of 5 ( 8 ) crystallizes as a dimeric LiF-adduct of an iminosilane, forming a LiF-four-membered ring. In thf 7 reacts with Me₃SiCl by a fluorine/chlorine exchange and 9 is obtained. In 9 lithium is coordinated with nitrogen, oxygen and two thf molecules, forming an (SiNOLi)-four-membered ring. 6 and 7 react with fluorosilanes to give tris(silyl)amines 10 – 12 .     

Tris(trimethylsilyl)silylamin und seine lithiierten und silylierten Derivate — Kristallstruktur des dimeren Lithium-trimethylsilyl-[tris(trimethylsilyl)silyl]amids

Tris(trimethylsilyl)silylamine and the lithiated and silylated Derivatives — X-Ray Structure of the dimeric Lithium Trimethylsilyl-[tris(trimethylsilyl)silyl]amide The ammonolysis of the chlor, brom or trifluormethanesulfonyl tris(trimethylsilyl)silane yields the colorless tris(trimethylsilyl)silylamine, destillable at 51°C and 0.02 Torr. The subsequent lithiation, reaction with chlor trimethylsilane and repeated lithiation lead to the formation of lithium tris(trimethylsilyl)silylamide, trimethylsilyl-[tris(trimethylsilyl)silyl]amine and finally lithium trimethylsilyl-[tris(trimethylsilyl)silyl]amide, which crystallizes in the monoclinic space group P2₁/n with a = 1 386.7(2); b = 2 040.2(3); c = 1 609.6(2) pm; β = 96.95(1)° and Z = 4 dimeric molecules. The cyclic Li₂N₂ moiety with Li? N bond distances displays a short transannular Li …? Li contact of 229 pm. The dimeric molecule shows nearly C₂-symmetry, so that one lithium atom forms agostic bonds to both the trimethylsilyl groups, the other one to the tris(trimethylsilyl)silyl substituents. However, the ⁷Li{¹H}-NMR spectrum displays a high field shifted singlet at —1.71 ppm. The lithiation of trimethylsilyl-[tris(trimethylsilyl)silyl]amine leads to a high field shift of the ²⁹Si{¹H} resonance of about 12 ppm for the Me₃SiN group, whereas the parameters of the tris(trimethylsilyl)silyl ligand remain nearly unaffected.     

‘Lone Pair’ and ‘CI Bond’ Ionization Energies of exo- and endo-2-Norbornyl Iodides

A PE-spectroscopic study of exo- and endo-2-norbornyl iodides suggests that the relative ability of the 2-norbornyl group to stabilize an electron deficiency on a substituent X (e.g. I) in exo- or endo-position depends on the location of the positive charge. There is no difference if the positive hole is strongly localized on on the substituent X (e.g. the 5p^?1 state of the title compounds). On the other hand, our results indicate that teh positive hole semi-localized in an exo-C? X bond is better stabilized by the 2-norbornyl group than a semi-localized, positive hole in an endo-C? X bond.     

Carbon Participation in the Solvolysis of 6- and 7-Substituted 2-Norbornyl p-Toluenesulfonates. Norbornanes,Part 11

The solvolysis rates and products of several 7-anti-substituted 2-endo-norbornyl p-toluenesulfonates 11 have been determined and compared with those of the previously reported 6-exo-substituted 2-exo-norbornyl p-toluenesulfonates 1. Although the number of bonds between the substituent and the reaction site is the same in the two series, the inductive effect of the substitutents is transmitted far more strongly in the 6-exo-2-exo-series 1 than in the 7-anti-2-endo-series 11 ; i.e. their inductivities differ widely. It is concluded that through space induction involves graded bridging of the substituent-bearing C-atom to the incipient cationic center at C(2) and that this involves differential bridging strain. The different reactivities of unsubstituted 2-exo- and 2-endo-norbornyl derivatives can then be ascribed to a stereoelectronic effect.     

Boron‐Doped,Carbon‐Coated SnO2/Graphene Nanosheets for Enhanced Lithium Storage

Heteroatom doping is an effective method to adjust the electrochemical behavior of carbonaceous materials. In this work, boron‐doped, carbon‐coated SnO₂/graphene hybrids (BCTGs) were fabricated by hydrothermal carbonization of sucrose in the presence of SnO₂/graphene nanosheets and phenylboronic acid or boric acid as dopant source and subsequent thermal treatment. Owing to their unique 2D core–shell architecture and B‐doped carbon shells, BCTGs have enhanced conductivity and extra active sites for lithium storage. With phenylboronic acid as B source, the resulting hybrid shows outstanding electrochemical performance as the anode in lithium‐ion batteries with a highly stable capacity of 1165 mA h g^?1 at 0.1 A g^?1 after 360 cycles and an excellent rate capability of 600 mA h g^?1 at 3.2 A g^?1, and thus outperforms most of the previously reported SnO₂‐based anode materials.     

Determination of boron in magnesium oxide by charged particle activation analysis

The determination of boron in magnesium oxide using the¹⁰B/p, /⁷Be,¹⁰B/d, n/⁷Be, and¹⁰B/d, n/¹¹C reactions is described. Lithium interferes the nuclear reactions leading to beryllium-7. Combination of a proton and deuteron irradiation, each followed by measurement of the induced beryllium-7 activity, allows a simultaneous determination of boron and lithium. The¹⁰B/d, n/¹¹C reaction is free from nuclear interferences. The boron concentration ranges from 1.5 to 850 g g^–1. The results obtained by the two methods are in good agreement.Senior Research Associate of the Belgian National Fund for Scientific Research.