Aluminium Trihalides Research Articles

Monomeric tri-coordinated bis(ferrocenyl)haloalumanes.

The reactions of the sterically demanding ferrocenyl lithium dimer (Fc*Li)2 (Fc* = 2,5-bis(3,5-di-t-butyl-phenyl)-1-ferrocenyl) with aluminum trihalides (AlCl3, AlBr3, and AlI3) to furnish the corresponding monomeric bis(ferrocenyl)haloalumanes are reported. In the case of the reaction with AlI3, an unexpected intramolecular 1,1'-aluminum migration in the ferrocenyl moiety was found to occur. Their monomeric structures with a tri-coordinated aluminum atom show affinitive Al⋯Fe interactions.

Lewis Acidity Trend of Boron and Aluminium Trihalides: If Not π Back-Bonding, What Else?

Lewis acidity trend of boron trihalides is a subject that has received a variety of explanations, and still, the simple π back-bonding based one is believed by most, perhaps because of its simplicity, irrespective of opposing findings. Herein we try to give an alternative explanation based on qualitative Molecular Orbital (MO) theory and support that quantitatively by Generalized Kohn-Sham Energy Decomposition Analysis. While the role of orbital overlap on the orbital interaction energy is widely known, the role of electronegativity of the atoms involved is often overlooked. Here we find that the Lewis acidity trend of boron and aluminium halides can be explained by the Wolfsberg-Helmholz (W-H) formula for resonance integral. The MO theory-based predictions are valid only when the orbital interactions are strong enough. In weakly interacting systems, the effect of orbital interactions can be overshadowed by other effects such as Pauli repulsion, dispersion, etc. Thus the Lewis acidity trend of boron and aluminium halides can vary depending on the strength of the interacting Lewis base. We believe that this work would enable one to gain a better understanding not only on the Lewis acidity of boron trihalides and its heavy analogs but also on a variety of related problems such as the stronger π acidity of CS compared to CO and weaker π bonding between heavy atoms.

Tuning Molecular Solar Thermal Properties by Modification of a Promising Norbornadiene Photoswitch

Carefully targeted modifications to the norbornadiene‐quadricyclane couple should give molecules with great potential for solar energy storage. Here we report the synthesis of derivatives of a well‐studied compound, 2‐cyano‐3‐anisyl norbornadiene (NBD5). The conjugation was extended by conversion of the nitrile into acrylonitrile and acrylate derivatives over two steps. Despite red‐shifting the absorbance properties, the metastable quadricyclanes exhibited extremely short lifetimes. Meanwhile, treatment of NBD5 with acetyl halides in the presence of aluminum trihalides led to the formation of 7‐acetyl norbornenes through a Wagner–Meerwein rearrangement. Subsequent transformations made it possible to synthesise norbornadienes with varying degrees of steric bulk at the 7‐position of the molecular scaffold. It was found that the bulkier this group was, the more stable the quadricyclane form. This reaction sequence allows for the synthesis of norbornadiene derivatives which are more suited to molecular solar thermal applications in domestic heating despite providing a slightly lower energy density.

Anti-Carboalumination of Alkynes Using Aluminum Trihalide and Silyl Ketene Imines: Stereo- and Regioselective Synthesis of Alkenylaluminum Compounds Bearing a Cyano Group.

An organoaluminum-free and catalyst-free anti-carboalumination of alkynes using aluminum trihalides and silyl ketene imines was developed. Three components, an alkyne, AlX3, and a silyl ketene imine, were simply mixed to give the alkenylaluminum bearing a cyano group with regioselectivity. Theoretical calculations revealed the effective activation of the alkyne by AlX3 to enhance the regioselective carboalumination. The synthesized alkenylaluminums were applicable to many organic transformations.

Electron-induced scattering dynamics of Boron, Aluminium and Gallium trihalides in the intermediate energy domain

ABSTRACTThis article is focused on the calculation of electron-induced ionisation and total scattering cross sections by Boron, Aluminium and Gallium trihalide molecules in the intermediate energy domain. The computational formalism, spherical complex optical potential has been employed for the study of these two scattering cross sections. The ionisation cross section has been derived from the inelastic cross section using a semi-empirical method called complex scattering potential-ionisation contribution (CSP-ic) method. We have also calculated the ionisation cross section using the BEB theory with Hartree–Fock and density functional theory (DFT- ωB97XD) orbitals so that a comparison can be made with the cross sections predicted by CSP-ic method. For this theoretical study, we have also calculated polarisability and bond length of some targets which were not found in literature using DFT/B3LYP in Gaussian 09 software.

Triel bonds-complexes of boron and aluminum trihalides and trihydrides with benzene

Triel bond is an interaction of an atom of the 13th Group of periodic system that acts as a Lewis acid with an electron rich species; it is analyzed here in complexes of benzene with boron and aluminum trihalides and trihydrides. MP2/aug-cc-pVTZ calculations were performed for these complexes and the interactions were analyzed with the use of Quantum Theory of “Atoms in Molecules.” It was found that benzene acts as the Lewis base not through a π-electron system but through one of carbon centers that is characterized by the most negative charge if compared with other carbon atoms of benzene. Thus, the B…C and Al…C bond paths are analyzed which correspond to preferable interactions; for some of complexes, the additional halogen (X)–carbon, X…C, intermolecular bond paths exist.

Triel Bonds, π-Hole-π-Electrons Interactions in Complexes of Boron and Aluminium Trihalides and Trihydrides with Acetylene and Ethylene.

MP2/aug-cc-pVTZ calculations were performed on complexes of aluminium and boron trihydrides and trihalides with acetylene and ethylene. These complexes are linked through triel bonds where the triel center (B or Al) is characterized by the Lewis acid properties through its π-hole region while π-electrons of C2H2 or C2H4 molecule play the role of the Lewis base. Some of these interactions possess characteristics of covalent bonds, i.e., the Al-π-electrons links as well as the interaction in the BH3-C2H2 complex. The triel-π-electrons interactions are classified sometimes as the 3c-2e bonds. In the case of boron trihydrides, these interactions are often the preliminary stages of the hydroboration reaction. The Quantum Theory of “Atoms in Molecules” as well as the Natural Bond Orbitals approach are applied here to characterize the π-hole-π-electrons interactions.

Comprehensive study of the structure of aluminum trihalides from electron diffraction and computation

The molecular geometries of the complete series of aluminum trihalides, AlX3 (X = F, Cl, Br, and I), are discussed based on new gas-phase electron diffraction (GED) experiments (AlCl3 and Al2Cl6) and on the reanalysis of our previous GED data (for the rest of the series) with an improved and analogous treatment of the temperature effect on the average bond lengths. This is the first time that all structure analyses are based on GED experiments of homogeneous vapors; either as pure monomers or dimers. The structures of other small oligomers as well as those of the crystals of aluminum trihalides are also discussed.

Carboxylation of indoles and pyrroles with CO 2 in the presence of dialkylaluminum halides

The Lewis acid-mediated carboxylation of arenes with CO 2 has been successfully applied to 1-substituted indoles and pyrroles by using dialkylaluminum chlorides instead of aluminum trihalides. Thus, the carboxylation of 1-methylindoles, 1-benzyl-, and 1-phenylpyrroles proceeds regioselectively with the aid of an equimolar amount of Me 2AlCl under CO 2 pressure (3.0 MPa) at room temperature to afford the corresponding indole-3-carboxylic acids and pyrrole-2-carboxylic acids in 61–85% yields, while the same treatment of 1,2,5-trimethylpyrrole affords the 3-carboxylic acid in 52% yield.

Aluminium and gallium trihalide adducts of 2,4,6-triorganylborazines and the synthesis of triorganylborazinium tetrabromoaluminates1

Borazines of type R3B3N3H3 (R = Me, Et, i-Pr, t-Bu, Ph) add AlBr3 and GaCl3 in a 1:1 ratio to one of its N atoms. During this process the planarity of the borazine is lost. The ring system of the adducts show a semi chair conformation. HBr gas reacts with R3B3N3H3 . AlBr3 in toluene with formation of hitherto unknown borazinium tetrabromo aluminates (R3B3N3H4) + (AlBr4). The ring system of the cation is almost planar but it shows like the adducts three different B-N bond lengths.

Novel diaminoaluminum halides and a diaminoaluminum hydride: 1,3,2-Diazaalumina-[3]ferrocenophanes

The dilithiated derivative 2 of 1,1′-bis(trimethylsilylamino)ferrocene ( 1) reacts with the pyridine adducts of the aluminum trihalides AlX 3 (X = Cl, Br, I) to give the respective 1,3,2-diazaalumina-[3]ferrocenophanes ( 4b, c, d) as pyridine adducts. The fluoride 4a could not be obtained in this way. The reaction of 1,1′-bis(trimethylsilylamino)ferrocene ( 1) with the dimethyl(ethyl)amine- or pyridine adduct of aluminium trihydride gave the 1,3,2-diazaalumina-[3]ferrocenophanes ( 5) and ( 6) as the amine and pyridine adducts, respectively. Treatment of 5 with trimethyltin fluoride afforded the adduct 7 with an Al–F function. Addition of pyridine converted 7 into the desired pyridine adduct of the fluoride ( 4a). The molecular structures of the pyridine adducts 4a, 4b, 4c and 6 were determined by X-ray analysis. The pyridine is in the trans-position relative to the N–Si bond vectors, and temperature dependent solution-state NMR spectra prove that prominent structural features are retained in solution.

Molecular Structure of the Aluminum Halides, Al2Cl6, AlCl3, Al2Br6, AlBr3, and AlI3, Obtained by Gas-Phase Electron-Diffraction and ab Initio Molecular Orbital Calculations

Gas-phase electron-diffraction (GED) data together with results from ab initio molecular orbital and normal coordinate calculations have been used to determine the structures of the aluminum trihalides AlX3 (X = Cl, Br, I) and the chloride and bromide dimers Al2Cl6 and Al2Br6. No monomeric species were detected in the vapors of Al2Cl6 at the experimental temperature of 150 °C, nor in Al2Br6 at167 °C, but the vapors of AlCl3 at 400 °C and AlBr3 at 330 °C contained respectively 29 (3)% and 7 (4)% dimer and the AlI3 at 300 °C about 8% I2. The known equilibrium symmetry of the dimers is D2h, but the molecules have a very low-frequency, large-amplitude, ring-puckering mode that lowers the thermal average symmetry to C2v. The effect of this large-amplitude mode on the interatomic distances was handled by dynamic models of the structures which consisted of a set of pseudoconformers spaced at even intervals along the ring-puckering angle 2Φ. The ring-puckering potential was assumed to be V(Φ) = V40Φ4 + V20Φ2, and...

Tetramethylpiperidine–Alane Adducts tmpH · AlX3 (X = Cl, Br, I) and tmpH · AlH2Cl: Synthesis, Solution Behavior, and X-ray Crystal Structures⋆

2,2,6,6-Tetramethylpiperidine (tmpH) reacts smoothly with aluminum trihalides AlX3 (X = Cl, Br, I) and monochloroalane AlH2Cl · 2 thf to give the addition compounds tmpH · AlX3 (X = Cl, Br, I) and tmpH · AlH2Cl, respectively. These adducts of the secondary amine tmpH are stable and do not undergo intramolecular elimination of HX or H2 with formation of the aminoalanes tmpAlX2 or tmpAl(H)Cl. In the solid state, tmpH · AlX3 (X = Cl, Br, I) and tmpH · AlH2Cl are tetracoordinated molecular adducts. While this is also true for solutions of tmpH · AlX3 (X = Br, I) and tmpH · AlH2Cl, the compound tmpH · AlCl3 dissolves in CH2Cl2 as the salt [tmpAlCl3]tmpH2 and the adduct tmpH · Al2Cl6, as is evident from its NMR spectra and from conductivity measurements. This behavior is supported by a semiempirical AM1 calculation.

Untersuchungen zum chemischen Transport von YX3 mit AlX3 und zur Existenz von gasförmigen und festen Komplexen YAl3 X12 (X = Br, I) / Investigations on the Chemical Transport Reaction of YX3 with AlX3 and on the Existence of Gaseous and Solid Complexes YAl3 X12 (X = Br, I) H

Abstract The dominant gaseous complexes YAl3Br12 and YAl3I12 were generated in the chemical trans­port reactions of YBr3 with AlBr3 and YI3 with AlI3. The enthalpy of formation ΔH0 B(YAl3Br12,g,298) = -484,5 ± 6 kcal/mol and the standard entropy S°(YA13B12,g,298) = 290,0 ± 7,5 cal/K·mol have been calculated. It follows from total pressure measurements of mixtures of YBr3,s with AlBr3,1 and YI3,s with AlI3,1 respectively, that complexes YAl3Br12,s and YAl3I12,s do not exist up to the boiling points of the aluminium trihalides.

Structure and dynamics of molten aluminium and gallium trihalides

Results of Raman scattering experiments combined with ab initio molecular orbital calculations are presented on the structure and vibrational properties of molten GaI 3 , GaBr 3 , AlCl 3 , and AlBr 3 . It is confirmed that, to a high degree, all of these compounds have in the molten state a dimer structure, represented by M 2 X 6 , consisting of two tetrahedra sharing a halide edge. It is shown that in AlCl 3 the melting process leads to a drastic change in the vibrational spectrum, whereas in the remaining salts the crystalline peak positions are essentially preserved

Reaction of monoterpenoids with hydrogen sulphide to form thiols and epi‐sulphides of potential organoleptic significance

AbstractReactions of limonene, α‐pinene, α‐ and γ‐terpinene, terpinolene, car‐3‐ene and pulegone with hydrogen sulphide in the presence of aluminium trichloride or tribromide at c. 0°C yielded mixtures of thiols and sometimes additionally bridged epi‐sulphides of the monoterpenoids in yields up to 20%. Reaction of limonene with elemental sulphur, in contrast, produced only the bridged compounds together with complex polysulphides.In total, nineteen sulphur‐containing terpenoids were characterized, of which eight were new compounds. Four‐, five‐ and six‐membered rings containing sulphur were present in the epi‐products, the most favoured ring‐size being five. The main product from reaction of limonene or α‐pinene with hydrogen sulphide–aluminium trihalide was p‐menth‐1‐en‐8‐thiol which is responsible for the characteristic flavour of grapefruit. The main product from pulegone was 8‐mercapto‐truns‐p‐menth‐3‐one an important component of Buchu leaf oil. A major, unexpected product from the reaction of car‐3‐ene was cis‐1,3,3,6‐tetramethyl‐2‐thia‐bicyclo[2.2.1]heptane, in which ring contraction had occurred to yield the iridoid monoterpenoid skeleton.

Dimethylsiloxy-aluminiumdihalide dimers. Molecular structures of [Me 2HSiOAlX 2] 2 (X  Cl, I) and [Me 3SiOAl(BH 4) 2] 2

sym-Tetramethyldisiloxane Me 2HSiOSiHMe 2 is cleaved by aluminium trihalides AlX 3 (X  Cl, Br, I) to give dimethylhalosilanes Me 2HSiX and alumosiloxane dimers [Me 2HSiOAlX 2] 2 (x = (Cl, 1; Br, 2; I, 3). Treatment of 1 with four equivalents of methyllithium yields the dimeric tetramethylsiloxalane [Me 2HSiOAlMe] 2, 4, which is also available from Me 2HSiOSiHMe 2 and Me 2AlCl. Compounds 1–4 have been identified and characterized by their physical data, analytical data, NMR and mass spectra. The crystal structures of the dichloride and the diiodide dimers have been determined by single crystal X-ray diffraction studies. The molecules have a planar, centrosymmetrical SiOAl 2OSi skeleton with three-coordinate oxygen atoms and pseudo-tetrahedral four-coordinate aluminium atoms. Gallium trichloride cleaves methyl groups from sym-tetramethyldisiloxane to give methylgallium dichloride and polymeric by-products. Dimeric trimethylsiloxyaluminium-bis(tetrahydridoborate), 5, prepared in previous studies, has also been investigated by an X-ray diffraction study. The SiOAl 2OSi skeleton of the dimer [Me 3SiOAl(BH 4) 2] 2 resembles that of 1 and 3, but the aluminium atoms are hexacoordinated by two bidentate BH 4 groups and the two siloxy oxygen atoms.

ChemInform Abstract: Lewis Acid Mediated Condensation of Alkenols and Aldehydes. A Selective Synthesis of Tetrahydropyrans and Oxepanes.

AbstractThe allylic alcohols (III), prepared from the carbonyl compounds (I) and allylmagnesium bromide (II), are cyclized with the aldehydes (IV) in the presence of aluminum trihalides to form the cis‐substituted 4‐halotetrahydropyrans (V).

ChemInform Abstract: Dihalo(organothio)alanes, Preparation and Properties.

AbstractThe title compounds (IV) are prepared by three methods: the trimethylsilyl sulfides (I) react with the aluminum trihalides (II) at room temperature to form the adducts (III) which yield (IVa), (IVb), (IVd), and (IVe) upon thermolysis.

Molecular electronic structure of aluminium trihalide dimers and their quadrupole couplings by the SCF–MS molecular-orbital method

SCF–multiple scattering calculations have been performed on the aluminium trihalide dimers (Al2X6, X = F, Cl, Br, I), and the nuclear quadrupole constants of 27Al and the halides have been calculated except for the fluoride. The calculated quadrupole constants compare reasonably well with experiment except for Al2Cl6. The cause of the disagreement between the calculated and experimental quadrupole constants in Al2Cl6 is discussed. The calculated ionization potentials of Al2Cl6 agree with experiment better than those from an ab initio STO-2G calculation. The effect of the sphere sizes on the results has also been studied.