IR spectroscopic study of the interaction between trimethylgallium and arsine in the liquid phase

The formation of a donor-acceptor complex Me₃Ga · AsH₃ in a solution in liquid krypton at 130 K and in a binary liquid solution of those substances at 263 K was established by IR spectroscopy. In the latter case, Me₃Ga and AsH₃ react at an appreciable rate to form an amorphous product of composition Me_3-x ,GaAsH_3-x .Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2259–2262, September, 1996.     

The catalytic action of trimethylgallium on the reaction of alkynyllithium with epoxides

Trimethylgallium catalyzes the reaction of 1-lithio-1-alkynes with epoxides affording 3-alkyn-1-ols in good to excellent yields.     

Purity of III/V semiconductor precursors: trimethylgallium,triethylgallium, ethyldimethylindium,arsine, trimethylarsine and phosphine

The purities of the metallorganic chemical vapor deposition (MOCVD) reagents trimethylgallium [Ga(CH₃)₃], triethylgallium [Ga(C₂H₅)₃], ethyldimethylindium [In(CH₃)₂C₂H₅], arsine (AsH₃), phosphine (PH₃) and trimethylarsine [As(CH₃)₃] were evaluated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR). Both conventional 70-eV electron impact ionization and low-pressure chemical ionization were used to evaluate sample purities. The trimethylgallium sample is 79% pure with significant amounts of dimethylgallium chloride and fluoride (19%), tetramethylsilane (0.11%) and various hydrocarbons. The triethylgallium sample is 53% pure with large amounts of hydrocarbons (46%) and also ethyl chloride (0.7%) and hydrogen sulfide (0.08%). The ethyldimethylindium sample is 73% pure with trimethylindium (10%) and methyldiethylindium (18%) also present. One arsine sample is 99.999% pure whereas the other contains significant amounts of methylarsine (38 ppm), dimethylarsine (36 ppm) and hydroxyarsine (36 ppm). The phosphine sample is 99.4% pure with 0.57% N₂, 400 ppm NH₃ and 100 ppm PH₂CH₃. Four trimethylarsine samples show purities of 99.3–99.8% in the liquid. Impurities observed are N₂, O₂ H₂S, PH₃, HCl, S(CH₃), Si(CH₃)₄, AsH₃, Ge(CH₃)₄ and Ar. Overall, the samples are typically less pure than stated, except for one arsine sample. The impurities detected are volatile and possible difficult to detect by conventional methods. Improvements in MOCVD reagent purities and their analysis will be required.     

Direct determination of arsine in gases by inductively coupled plasma-dynamic reaction cell-mass spectrometry

Reliable determination of arsine (AsH₃) in gases is of great importance due to stringent regulations associated with health, safety and environmental issues. It is, however, challenging for an analyst to determine trace airborne arsine concentrations without specifically designed collection procedures using adsorption, desorption, dissolution or impinging techniques. To circumvent such technical barrier, we have newly developed a direct analytical method, characterized by introduction of an arsine gas sample into stable plasma stream, followed by gas-phase oxidation of arsine with molecular oxygen in a dynamic reaction cell (DRC) equipped within the inductively coupled plasma-mass spectrometry (ICP/MS) system, followed by subsequent detection of AsO⁺ ion. This preliminary work used trace arsine concentrations (161 μg m⁻³, 322 μg m⁻³, and 645 μg m⁻³) gravimetrically prepared in N₂ balance. The proposed method was optimized for the important experimental parameters such as the flow rates of the reaction gas, the arsine sample, and the carrier gas. This method was then validated by demonstrating good figure-of-merits including the low limit of detection (0.10 μg m⁻³), good linearity (r² > 0.9915), low measurement uncertainty (0.66%), and high speed of analysis (<6 min). The proposed method is expected to be potentially applicable to the determination of arsine in real workplace air after appropriate modifications are made.     

Reversible adduct formation of trimethylgallium and trimethylindium with ammonia

We have used gas-phase infrared spectroscopy to determine the equilibrium constant (K(p)) for the formation of (CH(3))(3)Ga:NH(3) and (CH(3))(3)In:NH(3) adducts in the 80-230 degrees C range. In this temperature range, and at reactant concentrations typically used for metal organic chemical vapor deposition, the dominant chemical reaction is reversible adduct formation/dissociation. Reaction enthalpies and entropies are extracted from the temperature dependence of K(p), yielding DeltaH(Ga) = -16.3 +/- 0.5 kcal/mol, DeltaS(Ga) = -32.4 +/- 1.2 eu, and DeltaH(In) = -15.0 +/- 0.6 kcal/mol, DeltaS(In) = -30.3 +/- 1.4 eu. These results will aid current and future modeling efforts, as well as advance our general understanding of the group-III nitride deposition process.     

Reactions of trimethylgallium with silicon hydrides,germane and diborane

Methylation of SiH₄, MeSiH₃, Si₂H₆, GeH₄ and B₂H₆, but not of PH₃ or AsH₃, was observed during reaction (230–324°C) with GaMe₃. The products from the SiH₄ and Si₂H₆ reactions were MeSiH₃, Me₂SiH₂ and Me₃SiH. The GeH₄-derived products were similar, with Me₄Ge also being formed. The only methylated products from B₂H₆ was BMe₃. The silane reactions were surface-catalyzed (presumably by surface hydroxyl groups), while those of GeH₄ and B₂H₆ may have occurred via gas-phase free radical processes.     

The effect of molybdenum(VI) on the production of arsine by the tetrahydroborate(III) reaction

Molybdenum(VI) increases signals in the determination of arsenic after reduction by tetrahydroborate(III). An increase in the signal by up to two-and-a-half fold is observed when arsenic(III) is determined in the presence of sulphuric and hydrochloric acid concentrations of 0.01-0.02M. The enhancement effect disappears at higher acid concentrations and is eliminated by the presence of L-cysteine. Signals from other hydride-forming elements (antimony, bismuth and tin) were reduced in the presence of molybdenum(VI). Reduction of interferences in the hydride-forming reaction from nickel and cobalt is observed, so that the range of tolerance of these elements is extended by one and two orders of magnitude, respectively. The interference reducing effect is not as profound as that observed with L-cysteine.     

Computational examination of the electrophilic reaction on oxidative polymerization of phenyltrimethylsilane with sulfur chloride

Phenyltrimethylsilane possesses a higher HOMO energy (–9.34 eV) than nonsubstituted benzene (>0.41 eV). The π electron of the phenyltrimethylsilane localizes on the benzene ring at the ipso position rather than at the para position. Two center energies calculated by the MNDO-PM3 method indicate that the C? Si bond is facilitated to cleave in comparison with the C? H (para position) one of the benzene ring. Phenyltrimethylsilane and phenyl bis(trimethylsilane) were polymerized with sulfur chloride through the cationic oxidative polymerization. The product is isolated as oligo(p-phenylene sulfide), with a melting point of 150–190°C. An electrophile attacks the carbon atom linked to the Si atom in phenyltrimethylsilane. The new synthetic route of PPS can be established on the basis of the computational calculation.     

Complex formation of trimethylaluminum and trimethylgallium with ammonia: evidence for a hydrogen-bonded adduct

We have investigated the formation of gas-phase adducts of trimethylaluminum and trimethylgallium with ammonia using room-temperature Fourier transform infrared experiments and density functional theory calculations. Our results indicate for the first time that, at higher partial pressures, a product distinct from the well-known (CH3)3M:NH3 adduct grows in for both M = Al and M = Ga. Comparison of the experimental and calculated IR spectra, along with calculations of the energetics, indicates that this second product is the result of hydrogen bonding of a second NH3 molecule to the (CH3)3M:NH3 adduct and can be written as (CH3)3M:NH3...NH3. The binding energy of this hydrogen-bonded adduct is calculated to be 26.8 kcal/mol for M = Al and 18.4 kcal/mol for M = Ga and is lower in energy (more stable) relative to the 1:1 (CH3)3M:NH3 adduct by 7.2 kcal/mol for M = Al and 6.6 kcal/mol for M = Ga. In contrast, an alternative complex involving the formation of two separate M-N donor-acceptor bonds, which is written as H3N:(CH3)3M:NH3, is calculated to be lower in energy relative to (CH3)3M:NH3 by only 0.1 kcal/mol for M = Al and 0.2 kcal/mol for M = Ga and is not observed experimentally. These results show that hydrogen bonding plays an important role in the interaction of ammonia with metal organic precursors involving Al, Ga, and In, under typical metal organic chemical vapor deposition AlGaInN growth conditions.     

The reaction of pyridazinones with nucleophiles. An unusual reaction with cyanide

Studies on the synthesis of pyridazinone analogues of pyridone cardiotonics are reported. The synthetic scheme involves the reaction of pyridazinones and chloropyridazinones with nucleophiles. Addition occurred twice with cyanide as the nucleophile, thus providing a novel dicyanopyridazinone.     

Infrared matrix isolation spectroscopy of trimethylgallium,trimethylaluminium and triethylaluminium

Infrared spectra (4000-300 cm⁻¹) of the title aluminium trialkyls are reported both for the dimers and the monomers. Spectra of monomeric (CH₃)₃Al and (CH₃CH₂)₃Al, obtained by dissociation of the dimers at 300 and 80°C, respectively, are reported for the first time. The spectra of matrix isolated (CH₃)₃Al and (CH₃)₃Ga are discussed in terms of a planar skeleton with rotational tunnelling of the methyl groups, i.e. symmetry group G₃₂₄ or effective point symmetry D_3h. Monomeric (CH₃CH₂)₃Al has been treated in a similar manner although the assignments of the ethyl modes are more complex. The interpretation of the spectra is supplemented with normal coordinate calculations. Controlled dimerization of matrix isolated monomeric (CH₃)₃Al by annealing indicates a mechanism proceeding via a single-bridged intermediate.     

Preparation of complexes from trimethylgallium and alkali metal hydrides

Conclusions Monohydride complexes of type MGa(CH₃)₃H are formed when trimethylgallium is reacted with alkali metal hydrides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 126–127, January, 1973.     

An examination of the kinetic compensation effect

The “kinetic compensation effect” arises from deficiencies in the Arrhenius equation. Determination of the pre-exponential factor generally comprises only the reconciliation of the expression of the temperature dependence of the rate (the exponential term) with the observed rate. The applicability of the Arrhenius equation to a particular reaction could be tested by finding constancy or a predictable variation in the “frequency factor” with changes in experimental conditions or sample treatment or history.