Element Halides Research Articles

A solar energy driven thermochemical cycle based integrated system for hydrogen production

In this study, an assessment of a newly developed solar energy-driven thermochemical cycle for hydrogen generation and potentially injection into the natural gas pipeline is performed. The hydrogen, produced by the heavy element halide cycle, is blended with natural gas at particular ratios. A blend of 80% natural gas and 20% hydrogen by volume is supplied to the community for the gas turbine system, gas cooker, and combi boiler. The desalination units are integrated to produce freshwater for a community, which potentially consists of 10,000 houses. The present integrated system is then analyzed through the energy and exergy approaches. The parametric studies are further performed for different volumetric hydrogen ratios, ambient temperature, and the number of houses. Here, 0.005 kg/s of hydrogen and 0.19 kg/s of natural gas are provided to the gas turbine system to generate electricity and heat. A heat recovery steam generator is utilized both for organic Rankine cycle and multi-effect distillation unit. A total of 4.5 MW electricity is generated by the gas turbine and the organic Rankine cycles. Moreover, a total of 34.62 kg/s of freshwater is provided by two specific reverse osmosis and multi-effect distillation units. The overall exergetic and energetic efficiencies of the present integrated system are obtained as 21.3% and 26.1% for the selected operating conditions.

Cycloisomerization of enynones by aluminum halides: construction of bicyclo[3.1.0]hexanes by introducing halides

Cycloisomerization of 7-en-2-ynone with an aluminum halide gives different cyclic products from those with BF3 as a homologous element halide.

In Ukrainian

Experimental data and the results of theoretical modeling of the spatial structure and chemical properties of isolated particles (molecules and clusters) characterized by the presence of hypercoordinated atoms and the molecular crystals formed by them have been analyzed. Methods of describing the distribution of electron density in molecular crystals and their polymorphism are considered. The influence of the chemical nature of the molecules of binary compounds on their capability to associate and form clusters is described, and the transition from dispersion interaction to coordination bonds in such structures is traced.The review highlights the properties of many dimers, trimers and oligomers of hydrides and halides of chemical elements of different valence, clusters of elemental-organic and coordination (both inorganic and organic nature) compounds, polyhedral structures with non-classical coordination of atoms, in particular, metal carbohedrenes. The results of quantum chemical calculations using the methods of Hartree-Fock (HF), configurational interaction, electron density functional theory (DFT) and second-order Möller-Plesset perturbation theory (MP2) of the spatial structure and energy characteristics of the considered models are discussed. Theoretical results are compared with available experimental data.

Modeling of Thermogasdynamics and Thermal Processes of Volatile Halides of Elements of III, IV and VI Groups in Thermal Plasma of RF-IC Discharge at Atmospheric Pressure

Modeling of Thermogasdynamics and Thermal Processes of Volatile Halides of Elements of III, IV and VI Groups in Thermal Plasma of RF-IC Discharge at Atmospheric Pressure

Comparative Analysis of the Saturated Vapor Pressure of Halogenides of the Scandium Subgroup

Experimental values for saturated vapor pressure (Psat) of halides of the scandium subgroup are systematized for the purpose of analyzing and predicting unexplored Psat. Comparative calculations are used for analysis, making it possible to compare the sought Psat to basic values graphically (Psat for CaF2).. Generalized analytical expressions of the form $$\log P$$ −1/T for all halides of elements of the Sc subgroup and dependence $$\log P$$ − $$\log {{P}_{{{\text{Ca}}{{{\text{F}}}_{2}}}}}$$ at different temperatures are obtained using the least squares approach. Linear correlations of the form $$\log P$$ − $$\log {{P}_{{{\text{Ca}}{{{\text{F}}}_{2}}}}}$$ are used to estimate correctly unknown values Psat of halides of the subgroup Sc. The special position of scandium and fluorine in the subgroups of Mendeleev’s periodic table is confirmed by the considerable difference between the properties of fluorides and similar values for chlorides, bromides and iodides. It is shown that the properties of scandium halides differ from those of the corresponding lanthanum and yttrium halides, and the properties of fluorides differ sharply from those of chlorides, bromides, and iodides, which have close values. The possibility of estimating Psat for compounds of actinium and astatide is shown.

N‐Heterocyclic Silylene Main Group Element Chemistry: Adduct Formation, Insertion into E−X Bonds and Cyclization of Organoazides

AbstractInvestigations concerning the reactivity of the N‐heterocyclic silylene Dipp2NHSi (1, 1,3‐bis(2,6‐diisopropylphenyl)‐1,3‐diaza‐2‐silacyclopent‐4‐en‐2‐ylidene) towards selected alanes and boranes, elemental halides X2 (X=Br, I), selected halide containing substrates such as tin chlorides and halocarbons, as well as organoazides are presented. The NHSi adducts Dipp2NHSi⋅AlI3 (2), Dipp2NHSi⋅Al(C6F5)3 (3), and Dipp2NHSi⋅B(C6F5)3 (4) were formed by the reaction of Dipp2NHSi with the corresponding Lewis acids AlI3, Al(C6F5)3 and B(C6F5)3. Adducts 3 and 4 were tested with respect to their ability to activate small organic molecules, but no frustrated Lewis pair reactivity was observed. Reactions of Dipp2NHSi with Br2, I2, Ph2SnCl2 and Me3SnCl led to formation of Dipp2NHSiBr2 (5), Dipp2NHSiI2 (6), Dipp2NHSiCl2 (7) and {(Me3Sn)N(Dipp)CH}2 (8), respectively. The reaction with the halocarbons methyl iodide, benzyl chloride, and benzyl bromide afforded the insertion products Dipp2NHSi(I)(CH3) (9), Dipp2NHSi(Cl)(CH2Ph) (10) and Dipp2NHSi(Br)(CH2Ph) (11). Reaction of Dipp2NHSi with the organoazides Ad‐N3 (Ad=adamantyl) and TMS‐N3 (TMS=trimethylsilyl) led to the formation of 1‐Dipp2NHSi‐2,5‐bis(adamantyl)‐tetrazoline (12) and bis(trimethylsilyl)amido azido silane (13), respectively. For 2,6‐(diphenyl)phenyl‐N3 C−H activation occurs and a cyclosilamine 14 was isolated.

Disphenoidal Zero-Dimensional Lead, Tin, and Germanium Halides: Highly Emissive Singlet and Triplet Self-Trapped Excitons and X-ray Scintillation.

Low-dimensional metal halides have been researched as optoelectronic materials for the past two decades. Zero-dimensional halides of ns2 elements (Sn, Pb, Sb) have recently gained attention as highly efficient broadband light emitters. These compounds comprise discrete metal halide centers, isolated by bulky organic cations. Herein, we report isostructural halide complexes of Ge(II), Sn(II), and Pb(II) with a 1-butyl-1-methyl-piperidinium cation (Bmpip), featuring unusual disphenoidal coordination with a highly stereoactive lone pair. Spectrally broad, bright emission from highly localized excitons, with quantum efficiencies of up to 75%, is observed in blue to red spectral regions for bromides (for Pb, Sn, and Ge, respectively) and extends into the near-infrared for Bmpip2SnI4 (peak at 730 nm). In the case of Sn(II) and Ge(II), both singlet and triplet excitonic emission bands have been observed. Furthermore, Bmpip2SnBr4 and Bmpip2PbBr4 exhibit X-ray-excited luminescence (radioluminescence) with brightness being commensurate with that of a commercial inorganic X-ray scintillator (NaI:Tl).

Ylide-Functionalization via Metalated Ylides: Synthesis and Structural Properties.

The α-metallated ylides [Ph3P-C-Z]-M+ (with Z=SO2Tol or CN and M=Na or K) were used as versatile nucleophiles for the facile access to ylide-substituted compounds. Halogenations, alkylations, carbonylations and functionalization reactions with main group element halides were easily accomplished by simple trapping reactions with the appropriate electrophiles. X-ray crystallographic studies of all compounds - including the first structures of α-fluorinated P-ylides - showed remarkable differences in the ylide backbone depending on the substituents. In the fluorinated compounds, a change from a fully planar to a pyramidalized ylidic carbon centre was observed despite the strongly anion-stabilizing ability of the yldiide substituent. π-Donation from the ylide substituent also resulted in geometric restrictions depending on the steric and electronic properties of the introduced substituents.

Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts.

Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)C═N tBu, Ph2C═CH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).

Syntheses, Structures, and Infrared Spectra of the Hexa(cyanido) Complexes of Silicon, Germanium, and Tin.

The rare octahedral EC6 coordination skeleton type is unknown for complexes with coordination centers consisting of group 14 elements. Here, the first examples of such EC6 species, the hexacoordinate homoleptic cyanido complexes E(CN)62-, E = Si, Ge, Sn, have been synthesized from element halides SiCl4, GeCl4 and SnF4 and isolated as salts with PPN counterions (PPN+ = (Ph3P)2N+) on a scale of 0.2-1 g. Characterization by spectroscopic techniques and by structure determination through single crystal crystallographic methods show that these pseudohalogen complexes have effective octahedral symmetry in solution and in the solid state. Infrared spectra obtained in solution reveal that the T1 u symmetric IR-active vibrations in all three complexes have unusually small oscillator strengths. The observed reluctance of Si(CN)62-, Ge(CN)62-, and Sn(CN)62- to form from chloro-precursors was rationalized in terms of Gibbs free energies, which were found by ab initio calculations at the CCSD(T)-F12b/aug-cc-pVTZ(-PP)-F12 level of theory to be small or even positive. The work demonstrates that E(CN)62- complexes of silicon, germanium and tin are in fact stable at room temperature and exist as well-defined units in the presence of noncoordinating counterions. The results add to our understanding of the chemistry of pseudohalogens and structure and bonding.

Synthesis and attempted reductions of bulky 1,3,5-triazapentadienyl groups 2 and 13 halide complexes

Three extremely bulky 1,3,5-triazapentadienes, ArNNNH (ArNNN = N{C(But)=N(Ar)}2; Ar = Mes (mesityl), Dep (2,6-diethylphenyl), or Dip (2,6-diisopropylphenyl)) have been prepared and structurally characterized. These are readily deprotonated, yielding a series of lithium and potassium triazapentadienyl complexes, one of which, (DipNNN)Li, has been structurally characterized. Similarly, three monomeric triazapentadienyl magnesium iodide complexes, (ArNNN)MgI(OEt2), and a dimeric calcium counterpart, {(MesNNN)Ca(THF)(μ-I)}2, have been prepared. Attempts to reduce the former gave homoleptic bis(triazapentadienyl) magnesium complexes, (ArNNN)2Mg (Ar = Mes or Dep) as the main products. One reaction also gave a very low yield of the magnesium(I) dimer, {(DepNNN)Mg–}2, which was structurally characterized. In related chemistry, two triazapentadienyl boron difluoride compounds, (ArNNN)BF2 (Ar = Mes or Dep), have been synthesized, and unsuccessful attempts have been made to reduce these to boron(I) heterocycles. For sake of comparison, attempts have been made to prepare a series of related amino-substituted β-diketiminato group 13 element(I) heterocycles. Although these were also not successful, several group 13 element(III) halide complexes incorporating this ligand class have been characterized.

Structure of Hybrid Interpolymeric Complexes of Polyvinyl Alcohol and Halides of Second Group Elements

Density functional theory was used to investigate structure and properties of polyvinyl alcohol complexes with halides of second group elements XHal2 (X = Be, Mg, Ca, Zn, Sr, Cd, Ba, and Hg; Hal = F, Cl, Br, and I). PVA can form hybrid interpolymeric complexes with some of them. These complexes show double spiral structure of two types.

Reactivity of an amidinato silylene and germylene toward germanium(ii), tin(ii) and lead(ii) halides.

The coordination chemistry of an amidinato silylene and germylene toward group 14 element(ii) halides is described. The reaction of the amidinato silicon(ii) amide [LSiN(SiMe3)2] (1, L = PhC(NtBu)2) with SnCl2 and PbBr2 afforded the amidinato silylene-dichlorostannylene and -dibromoplumbylene adducts [L{(Me3Si)2N}SiEX2] (E = Sn, X = Cl (2); E = Pb, X = Br (3)), respectively, in which there is a lone pair of electrons on the Sn(ii) and Pb(ii) atoms. X-ray crystallography, NMR spectroscopy and theoretical studies show conclusively that the Si(ii)-E(ii) bonds are donor-acceptor interactions. Similar electronic structures were found in the amidinato germylene-dichlorogermylene and -dichlorostannylene adducts [L{(Me3Si)2N}GeECl2] (E = Ge (5), Sn (6)), which were prepared by treatment of the amidinato germanium(ii) amide [LGeN(SiMe3)2] (4) with GeCl2·dioxane and SnCl2, respectively.

Merging allylic C-H bond activation and C-C bond cleavage en route to the formation of a quaternary carbon stereocenter in acyclic systems.

This protocol describes a diastereoselective approach for the synthesis of complex molecular architectures containing two stereogenic centers in a 1,4 relationship, one of which being an all-carbon quaternary stereogenic center. Such molecules could be intermediates in the synthesis of steroids, for example. Conceived as a single-flask synthetic sequence from ω-ene cyclopropanes, the protocol involves a concerted allylic C-H and C-C bond activation promoted by the Negishi reagent (Cp2Zr(η2-butene)). This zirconium-promenade-based procedure affords bifunctionalized products in high diastereomeric ratios after reaction of ω-ene cyclopropanes with the Negishi complex, followed by a thermal treatment and sequential addition of two different electrophiles. The method proves to be particularly efficient when carbonyl compounds are used as first electrophiles and hydrogen or elemental halides are used as second electrophiles. In addition, it offers the opportunity to create new C-C bonds via remote functionalization of a (sp3)-C-H bond, a result of a copper or copper/palladium transmetalation step that extends the scope of the process to alkyl, acyl and aromatic halide compounds as second electrophiles. The typical described protocol allows the synthesis of the highly diastereo-enriched 2-((1R*,2S*)-2-butyl-2 propylcyclopropyl)ethanol and may provide a new entry to access complex molecular segments of natural products such as steroids or C30 botryococcene. It requires a simple reaction setup and takes ∼18.5 h to run the reaction and 2 h for isolation and purification.

Nucleophilic Transfer Reactions of the [Si(C2 F5 )3 ]- Moiety.

The tris(pentafluoroethyl)silanide anion is accessible by the deprotonation of Si(C2 F5 )3 H at low temperatures. Subsequent quenching of the resulting salt-like compounds with suitable electrophiles, such as transition-metal complexes or Group 14 element halides, leads to a plethora of novel tris(pentafluoroethyl)silane derivatives. This underlines the versatility of Li[Si(C2 F5 )3 ] as a powerful nucleophilic transfer reagent.

Reversible Dihydrogen Activation by Reduced Aryl Boranes as Main‐Group Ambiphiles

AbstractA new approach to main‐group H2 activation combining concepts of transition‐metal and frustrated Lewis pair chemistry is reported. Ambiphilic, metal‐like reactivity toward H2 can be conferred to 9,10‐dihydro‐9,10‐diboraanthracene (DBA) acceptors by the injection of two electrons. The resulting [DBA]2− ions cleave the H−H bond with the formation of hydridoborates under moderate conditions (T=50–100 °C; p<1 atm). Depending on the boron‐bonded substituents R, the addition is either reversible (R=C≡CtBu) or irreversible (R=H). The reaction rate is strongly influenced by the nature and the coordination behavior of the countercation (Li+ slower than K+). Quantum‐chemical calculations support the experimental observations and suggest a concerted, homolytic addition of H2 across both boron atoms. As proven by the successful conversion of Me3SiCl into Me3SiH, the system Li2[DBA]/H2 appears generally relevant for the hydrogenation of element–halide bonds.

Multinuclear Alkali Metal Complexes of a Triphenylene-Based Hexamine and the Transmetalation to Tris(N-heterocyclic tetrylenes) (Ge, Sn, Pb).

A C3-symmetric hexamine (LH6) based on the triphenylene and ortho-phenylenediamine (PDAH2) skeletons has been synthesized, and was partially or fully deprotonated upon treatment with alkali metal agents to afford amino-amido or diamido coordination sites. Four alkali metal complexes, the dinuclear [Na2(LH4)(DME)5] (1) and [K2(LH4)(DME)4] (2), trinuclear [K3(LH3)(DME)6] (3), and hexanuclear [Li6(L)(DME)6] (4), were obtained and used in transmetalation/ligand exchange with other metals. The hexalithium salt of the fully deprotonated ligand, [Li6L], reacted with heavier group 14 element halides to yield three tris(N-heterocyclic tetrylenes), the germylene [Ge3(L)] (5), stannylene [Sn3(L)] (6), and plumbylene [Pb3(L)] (7). The synthesis and crystal and electronic structures of these compounds are reported.

Transition metal-mediated donor-acceptor coordination of low-oxidation state Group 14 element halides.

The reactivity of tungsten carbonyl adducts of Group 14 element (Ge, Sn and Pb) dihalides towards the metal-based donors (η(5)-C5H5)Rh(PMe2Ph)2 and Pt(PCy3)2 was examined. When (η(5)-C5H5)Rh(PMe2Ph)2 was treated with the Lewis acid supported Ge(ii) complex, THF·GeCl2·W(CO)5, cyclopentadienyl ring activation occurred, whereas the analogous Lewis acidic units SnCl2·W(CO)5 and PbCl2 form direct adducts with the Rh complex to yield Rh-Sn and Rh-Pb dative bonds. Attempts to prepare metal coordinated element(ii) hydrides by adding hydride sources to the above mentioned rhodium-E(ii) halide complexes were unsuccessful; in each case insoluble products were formed along with regeneration of free (η(5)-C5H5)Rh(PMe2Ph)2. In a parallel study, ECl2·W(CO)5 (E = Ge or Sn) groups were shown to participate in E-Cl oxidation addition chemistry with (Cy3P)2Pt to give the formal Pt(ii) complexes ClPt(PCy3)2ECl·W(CO)5.

Reactions of the [B10H10]2− anion with nucleophiles in the presence of halides of group IIIA and IVB elements

The study deals with reactions of the closo-decaborate anion [B10H10]2− with a number of nucleophiles (cyclic ethers and thioethers, N,N-substituted amides, and nitriles) in the presence of Lewis acids, halides of Group IIIA and IVB elements (BF3 · Et2O, AlCl3, TiBr4, TiI4, ZrCl4, ZrI4, and HfCl4), which act as electrophilic inductors of the nucleophilic substitution. This group of reactions allows the preparation of closo-decaborate derivatives with one or two exopolyhedral substituents. The method is distinguished by high yields (more than 80%) and high regioselectivity of substitution and can also be used to prepare disubstituted closo-decaborate derivatives.

Conversion of zirconacyclopentadienes into metalloles: Fagan-Nugent reaction and beyond.

Metalloles are derivatives of cyclopentadiene in which the methylene unit is replaced by a heteroatom, such as S, Se, Te, N, P, As, Sb, Bi, Si, Ge, Sn, B, Al, Ga, and so on. Many metallole derivatives have been widely used as photovoltaic cells, organic light emitting diodes (OLEDs), chemical sensors, electrochromic devices, microelectronic actuators, and organic field effect transistors (OFETs). In the meantime, many of them showed promising biological actives. Due to the similarity to cyclopentadiene, the anionic forms of metalloles were also widely explored in coordination chemistry. As a result, development of a general method for the formation of metalloles from available starting materials is highly desired. In this Account, we outline formation of various p-block element metalloles from zirconacyclopentadienes. The zirconacyclopentadienes can be easily prepared from two molecules of alkynes and a low-valent zirconocene species "Cp2Zr(II)" (Cp = cyclopentadienyl). Fagan and Nugent first reported the formation of main group metalloles from zirconacyclopentadiene, which provided a versatile approach for the construction of metalloles, especially for the formation of metalloles in heavier p-block elements. To further expand the substrate scope, a number of stepwise conversions were developed, which involve 1,4-dimetallo- or dihalo-1,3-butadiene as intermediates from zirconacyclopentadienes. Here, four processes are classified based on direct and indirect conversion of zirconacyclopentadienes into metalloles. Direct reaction of zirconacyclopentadienes with element halides afforded heterocycles of main group elements, which provided a versatile method for the synthesis of metalloles. Nonetheless, the reaction scope was restricted to heavier p-block elements such as S, Se, P, As, Sb, Bi, Ge, Sn, Ga, and In. And these reactions usually suffered low yields and long reaction time. Transmetalation of zirconacyclopentadiene with copper chloride greatly enriched the zirconacyclopentadiene chemistry. The synthesis of stannoles and pyrroles from zirconacyclopentadienes has been developed in the presence of CuCl. The direct reaction of the zirconacyclopentadienes with SiCl4 or R2SiCl2 does not give the desired silacyclopendadiene derivatives, even in the presence of CuCl. It can be circumvented by using dilithiated dienes from diiododienes, which are easily prepared by the iodination of zirconacyclopentadienes using CuCl as an additive. Finally, an umpolung strategy, reaction of electrophilic 1,4-diiodo-1,3-butadiene with nucleophilic amine or sulfide reagents, was successfully used in the formation of pyrroles and thiophenes.