Gallium Trihalides Research Articles

Utilisation of a dianionic pentadentate ligand in group 13 chemistry

Using the pentadentate tetrapyrazolylpyridyl diborate (B2Pz4Py) ligand allowed for the isolation of overall seven group 13 complexes, which have been fully characterised and whose solid-state structures were obtained by single-crystal X-ray diffraction analysis. The aluminium chloride (1) and bromide (2) complexes as well as the gallium chloride (3) and iodide (4) complexes are accessible by deprotonation of the ligand precursors [B2Pz4LiPyH]2 with lithium hexamethyldisilazide and subsequent reaction with aluminium and gallium trihalides. Using indium(I) chloride instead gives rise to the indium(III) bis(trimethylsily)amide complex 5. Chloride abstraction from the aluminium(III) complex 1 using a combination of TlBArF24 and TlPF6 affords the related aluminium(III) fluoride complex 6 while using the gallium(III) complex 3 yields the dinuclear cationic PF2O2-bridged gallium(III) complex 7.

Coordination polymers and molecular complexes of group 13 metal halides with bis-pyridylethane: comparison with rigid N-containing ligands

Cationic 1D coordination polymers based on complexes of aluminium and gallium trihalides with 1,2-bis(4-pyridyl)ethane featuring double bridged bpa in gauche conformation.

Approaching Dissolved Species in Ammonoacidic GaN Crystal Growth: A Combined Solution NMR and Computational Study.

Solutions of gallium trihalides GaX 3 (X=F, Cl, Br, I) and their ammoniates in liquid ammonia were studied at ambient temperature under autogenous pressure by multinuclear (71Ga, 35Cl, 81Br) NMR spectroscopy. To unravel the role of pH, the analyses were done both in absence and in presence of ammonium halides, which are employed as mineralizers during ammonoacidic gallium nitride crystal growth. While gallium trifluoride and its ammoniate were found to be too sparingly soluble to give rise to a NMR signal, the spectra of solutions of the heavier halides reveal the presence of a single gallium‐containing species in all cases. DFT calculations and molecular dynamics simulations suggest the identification of this species as consisting of a [Ga(NH3)6]3+ cation and up to six surrounding halide anions, resulting in an overall trend towards negative complex charge. Quantitative 71Ga NMR studies on saturated solutions of GaCl3 containing various amounts of additional NH4Cl revealed a near linear increase of GaCl3 solubility with mineralizer concentration of about 0.023 mol GaCl3 per mol NH4Cl at room temperature. These findings reflect the importance of Coulombic shielding for the inhibition of oligomerization and precipitation processes and help to rationalize both the low solubility of gallium halides in neutral ammonia solution and, in turn, the proliferating effect of the mineralizer during ammonoacidic gallium nitride formation.

Structural variety of aluminium and gallium coordination polymers based on bis-pyridylethylene: from molecular complexes to ionic networks

Diverse molecular (0D and 1D) as well as ionic (0D, 1D, 2D, mixed 1D–2D) crystal structures of complexes of aluminium and gallium trihalides with bis(4-pyridylethylene) were obtained by solvent-free melt reactions.

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.

Glycolates and cellosolvates of metals as prospective materials for production of oxide powders and thin-film coatings

A method for producing a series of metal glycolates and cellosolvates, which are promising materials for the sol-gel and pyrolytic technologies for fabrication of powders and thin-layer oxide coatings by dissolution of metals in glycols and cellosolves in the presence of gallium trihalide as catalysts, is discussed. The dependence between catalytic activity of halides and the anion used is revealed.

ChemInform Abstract: Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides.

AbstractThe title preparation of α‐alkenyl esters has a broad substrate scope.

Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides.

A cross-coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3 took place to give the corresponding α-alkenyl esters. GaBr3 showed the most effective catalytic ability, whereas other metal salts such as BF3 ⋅OEt2 , AlCl3 , PdCl2 , and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti-carbogallation among GaBr3 , an enol derivative, and a silyl ketene acetal, followed by syn-β-alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover-limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn-β-alkoxy elimination and anti-carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon-oxygen bond in the β-alkoxy elimination process, which is the turnover-limiting step in the reaction between a vinyl ether and a silyl ketene acetal.

Selected boron, aluminum, and gallium trihalide and trihydride anions

Ab initio methods with flexible orbital basis sets are used to examine the electron binding strengths of tri-fluorides, tri-chlorides, and tri-hydrides of B, Al, and Ga. The adiabatic electron affinities are found to increase with increasing atomic number of the central atom. For any given central atom M (M=B, Al, Ga), the adiabatic and vertical electronic stability for MCl3 is larger than that of the corresponding MF3. The tri-hydrides have quite different electron binding strengths than the corresponding tri-halides. BH3 has a very small EA (ca. 0.02eV) and its anion is planar whereas the tri-halide anions and AlH3− and GaH3− are non-planar. AlH3 and GaH3 have considerably smaller EAs (ca. 0.3eV) than the Al and Ga tri-halides (0.9–1.8eV). In all, these anions provide species whose electron binding strengths span a considerable range (0.3–1.8eV).

(tert-Butyl isocyanide-κC)trichloridogallium(III)

The crystal structure of (tert-butyl isocyanide-κC)trichloridogallium(III), [GaCl3(C5H9N)], features the first reported isocyanide–gallium trihalide complex. The Ga—C—N—C fragment is essentially linear. The methyl fragments of thetert-butyl group are eclipsed with the chloride ligands on the Ga atom. The molecule does not, however, exhibit threefold crystallographic symmetry, as it crystallizes within theP21/cspace group.

ChemInform Abstract: Gallium Trihalide Catalyzed Sequential Addition of Two Different Carbon Nucleophiles to Esters by Using Silyl Cyanide and Ketene Silyl Acetals.

AbstractThe described method is applicable to aromatic, aliphatic and formic acid esters, and lactones as substrates giving the products with low to high yields.

Gallium trihalide catalyzed sequential addition of two different carbon nucleophiles to esters by using silyl cyanide and ketene silyl acetals.

A sequential addition of silyl cyanide and ketene silyl acetals to esters was achieved by a gallium trihalide catalyst to produce β-cyano-β-siloxy esters. This is the first example of the sequential addition of two different carbon nucleophiles to esters. The employment of lactones provided α,α-disubstituted cyclic ethers with a cyano group and an ester moiety. A variety of esters and lactones are applicable to this reaction system.

An Investigation of 1:1 Adducts of Gallium Trihalides with Triarylphosphines by Solid-State69/71Ga and31P NMR Spectroscopy

Several 1:1 adducts of gallium trihalides with triarylphosphines, X(3)Ga(PR(3)) (X=Cl, Br, and I; PR(3)=triarylphosphine ligand), were investigated by using solid-state (69/71)Ga and (31)P NMR spectroscopy at different magnetic-field strengths. The (69/71)Ga nuclear quadrupolar coupling parameters, as well as the gallium and phosphorus magnetic shielding tensors, were determined. The magnitude of the (71)Ga quadrupolar coupling constants (C(Q)((71)Ga)) range from approximately 0.9 to 11.0 MHz. The spans of the gallium magnetic shielding tensors for these complexes, δ(11)-δ(33), range from approximately 30 to 380 ppm; those determined for phosphorus range from 10 to 40 ppm. For any given phosphine ligand, the gallium nuclei are most shielded for X=I and least shielded for X=Cl, a trend previously observed for In(III)-phosphine complexes. This experimental trend, attributed to spin-orbit effects of the halogen ligands, is reproduced by DFT calculations. The signs of C(Q)((69/71)Ga) for some of the adducts were determined from the analysis of the (31)P NMR spectra acquired with magic angle spinning (MAS). The (1)J((69/71)Ga,(31)P) and ΔJ((69/71)Ga, (31)P) values, as well as their signs, were also determined; values of (1)J((71)Ga,(31)P) range from approximately 380 to 1590 Hz. Values of (1)J((69/71)Ga,(31)P) and ΔJ((69/71)Ga,(31)P) calculated by using DFT have comparable magnitudes and generally reproduce experimental trends. Both the Fermi-contact and spin-dipolar Fermi-contact mechanisms make important contributions to the (1)J((69/71)Ga,(31)P) tensors. The (31)P NMR spectra of several adducts in solution, obtained as a function of temperature, are contrasted with those obtained in the solid state. Finally, to complement the analysis of NMR spectra for these adducts, single-crystal X-ray diffraction data for Br(3)Ga[P(p-Anis)(3)] and I(3)Ga[P(p-Anis)(3)] were obtained.

Structural and thermodynamic properties of molecular complexes of aluminum and gallium trihalides with bifunctional donor pyrazine: decisive role of Lewis acidity in 1D polymer formation

Solid state structures of group 13 metal halide complexes with pyrazine (pyz) of 2:1 and 1:1 composition have been established by X-ray structural analysis. Complexes of 2:1 composition adopt molecular structures MX3·pyz·MX3 with tetrahedral geometry of group 13 metals. Complexes of AlBr3 and GaCl3 of 1:1 composition are 1D polymers (MX3·pyz)∞ with trigonal bipyramidal geometry of the group 13 metal, while the weaker Lewis acid GaI3 forms the monomeric molecular complex GaI3·pyz, which is isostructural to its pyridine analog GaI3·py. Tensimetry studies of vaporization and thermal dissociation of AlBr3·pyz and AlBr3·pyz·AlBr3 complexes have been carried out using the static method with a glass membrane null-manometer. Thermodynamic characteristics of vaporization and equilibrium gas phase dissociation of the AlBr3·pyz complex have been determined. Comprehensive theoretical studies of (MX3)n·(pyz)m complexes (M = Al, Ga; X = Cl, Br, I; n = 1, 2; m = 1-3) have been carried out at the B3LYP/TZVP level of theory. Donor-acceptor bond energies were obtained taking into account reorganization energies of the fragments. Computational data indicate that the formation of (MX3·pyz)∞ polymers with coordination number 5 is only slightly more energetically favorable than the formation of molecular complexes of type MX3·pyz for X = Cl, Br. It is expected that on melting (MX3·pyz)∞ polymers dissociate into individual MX3·pyz molecules. This dovetails with low melting enthalpies of the (MX3·pyz)∞ complexes. Polymer stability decreases in the order AlCl3 > AlBr3 > GaCl3 > AlI3 > GaBr3 > GaI3. For MI3·pyz complexes computations predict that the monomeric structure motif is more energetically favorable compared to the catena polymer. These theoretical predictions agree well with the experimentally observed monomeric complex GaI3·pyz in the solid state. Thus, the Lewis acidity of the group 13 halides may play a decisive role in the formation of 1D polymeric networks.

Recent applications of gallium and gallium halides as reagents in organic synthesis

This review highlights the application of gallium metal and gallium halides as reagents in organic synthesis. Owing to their unique catalytic properties, gallium trihalides are considered effective Lewis acids which can activate several functional groups under extremely mild conditions. Gallium halides have been successfully employed as Lewis acid catalysts in various organic transformations such as alkylation, allylation, radical reactions, cycloaddition reactions, Friedel–Craft's reactions and various coupling reactions. This review seeks to update organic chemists about the potential application of gallium halides in the synthesis of a wide variety of chemical building blocks.

Donor−Acceptor Complexes of Borazines

Donor-acceptor complexes of borazine (BZ) and its substituted derivatives with Lewis acids (A = MCl(3), MBr(3); M = B, Al, Ga) and Lewis bases (D = NH(3), Py) have been theoretically studied at the B3LYP/TZVP level of theory. The calculations showed that complexes with Lewis bases only are unstable with respect to dissociation into their components, while complexes with Lewis acids only (such as aluminum and gallium trihalides) are stable. It was shown that formation of ternary D→BZ→A complexes may be achieved by subsequent introduction of the Lewis acid (acceptor A) and the Lewis base (donor D) to borazine. The nature of substituents in the borazine ring, their number, and position were shown to have only minor influence on the stability of ternary D→BZ→A complexes due to the compensation effect. Much weaker acceptor properties of borazine are explained in terms of large endothermic pyramidalization energy of the boron center in the borazine ring. In contrast to borazine, binary complexes of the isoelectronic benzene were predicted to be weakly bound even in the case of very strong Lewis acids; ternary DA complexes of benzene were predicted to be unbound. The donor-acceptor complex formation was predicted to significantly reduce both the endothermicity (by 70-95 kJ mol(-1)) and the activation energy (by 40-70 kJ mol(-1)) for the borazine hydrogenation. Thus, activation of the borazine ring by Lewis acids may be a facile way for the hydrogenation of borazines and polyborazines.

Vapor Pressures of Gallium Trifluoride, Trichloride, and Triiodide and Their Standard Sublimation Enthalpies

The vapor pressures of gallium trihalides GaF3, GaCl3, and GaI3 were measured by a torsion effusion apparatus, and their temperature dependences fit the following equations: log(p/Pa) = (14.30 ± 0.30) − (12600 ± 200)/(T/K) (from 808 to 958 K), log(p/Pa) = 13.80 − 3800/(T/K) (from 289 to 308 K), and log(p/Pa) = (14.00 ± 0.50) − (5130 ± 150)/(T/K) (from 345 to 401 K) for GaF3, GaCl3, and GaI3, respectively. Both GaF3 and GaI3 vaporize practically congruently in monomeric form while GaCl3 is in dimer form. Treating the vapor pressures by second- and third-law methods, the selected standard enthalpies ΔH°(298 K) = (252 ± 4) kJ·mol−1, (89 ± 2) kJ·mol−1, and (100.5 ± 2.0) kJ·mol−1 associated with the sublimation of GaF3, GaCl3, and GaI3, respectively, were obtained.

Chelating ionic versus bridged molecular structures of group 13 metal complexes with bidentate ligands

Complexes of aluminum and gallium trihalides with ethylenediamine ( en) and N, N, N′, N′-tetramethylethylenediamine ( tmen) of 2:1 composition have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. In contrast to known molecular complexes of hydrido and methyl-substituted analogs, these solid complexes adopt ionic structures of the general type [M 1X 2LL] +[M 2X 4] − (X = Br, I; M 1, M 2 = Al or Ga; LL = en, tmen). Quantum chemical computations at B3LYP/LANL2DZ(d,p) level of theory showed that molecular complexes M 1X 3LLM 2X 3 are more stable in the gas phase compared to the [M 1X 2LL] +[M 2X 4] − ion pairs. Ionic complexes of metal halides with en and tmen are predicted to exist in the solid state due to strong X − affinity of MX 3 and favorable crystallization energy. Considerably lower H − and CH 3 − affinity of MH 3 and M(CH 3) 3 favors molecular structures for complexes of hydrides and methyl derivatives both in the gaseous and condensed state. Comparative case study between complexes of AlCl 3 with ammonia and en points out that AlCl 3NH 3 adduct exist in molecular form due to strong intermolecular H⋯Cl interaction. Molecular structure of GaBr 3NH 3 adduct was experimentally confirmed by single crystal X-ray diffraction analysis.

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.

Structure and diffusion in aluminium and gallium trihalide melts from simulations based on intramolecular force laws

Diffraction studies of the liquid structure of AlCl3, AlBr3, GaBr3 and GaI3 close to their respective freezing points have revealed fourfold coordination of the trivalent metal ions, consistent with dimeric M2X6 molecules being the dominant species. We evaluate the species-resolved pair distribution functions and liquid structure factors in all these melts by carrying out classical molecular-dynamics simulations, based on polarizable-halogen force laws that were determined on isolated molecular monomers and dimers in the gaseous phase. We also report results for mean-square displacements and diffusion coefficients of the two species in each melt. The model reproduces the main features of the total neutron-diffraction structure factors, showing peaks due to intermediate-range order and to charge and density short-range order, and accounts for the experimental data at a good quantitative level. Direct simulation of the pair distribution functions yields agreement with the diffraction data on metal–halogen and halogen–halogen bond lengths in the melt and on the stability of the first-neighbour shell of the metal ions. We examine the temperature dependence of the liquid structure in our models for GaBr3 and AlCl3 and emphasize the structural role of van der Waals interactions between the halogens.