Michael B. Power

Oxidation and hydrolysis of tris-tert-butylgallium

Abstract The oxidation of GaBu3t with oxygen leads to the formation of [Bu3tGa(μ-OOBut)]2 (1). The thermolysis of 1 yields the alkoxide complex [Bu2tGa(μ-OBut)]2 (2), which may also be prepared directly from GaBu3t and ButOH. The reaction of [ButGaCl(μ-Cl)]2 (3) with oxygen does not result in its oxidation, but may be used in its purification due to the oxidation of the GaBu3t impurities. The hydrolysis of GaBu3t in thf solution, in which it exists as the solvated complex 4, results in the formation of the monomeric hydroxide complex Bu2tGa(OH)(thf) (5). In contrast, the use of non-coordinating solvents results in the trimeric hydroxide [Bu2tGa(μ-OH)]3 (6). Compound 6 is also isolated from the reaction of Bu2tGaCl(thf) (7) with KOH in refluxing thf. The solid state pyrolysis of 6 gives the polymeric oxide [ButGa(O)]x (8). All the compounds have been characterized by NMR, IR and mass spectroscopy, while the structures of 1, 2 and 3 have been confirmed by X-ray crystallography. Compound 1 crystallizes in the monoclinic space group C2/m with a = 16.375(2), b = 11.323(2), c = 8.895(2) A and β = 116.710(12)°, Z = 2, R = 0.042 and Rw, = 0.038. Compound 2 crystallizes in the orthorhombic space group Pbca with a = 15.0072(17), b = 9.8399(8), c = 18.3840(15) A, Z = 4, R = 0.037 and Rw = 0.041. Compound 3 crystallizes in the monoclinic space group P21/c with a = 6.816(4), b = 6.743(5), c = 17.062(10)A and β = 95.87(4)°, Z = 2, R = 0.042, Rw = 0.049.

Enhancement of photoluminescence intensity of GaAs with cubic GaS chemical vapor deposited using a structurally designed single-source precursor

A two order‐of‐magnitude enhancement of photoluminescence intensity relative to untreated GaAs has been observed for GaAs surfaces coated with chemical vapor‐deposited GaS. The increase in photoluminescence intensity can be viewed as an effective reduction in surface recombination velocity and/or band bending. The gallium cluster [(t‐Bu)GaS]4 was used as a single‐source precursor for the deposition of GaS thin films. The cubane core of the structurally characterized precursor is retained in the deposited film producing a cubic phase. Furthermore, a near‐epitaxial growth is observed for the GaS passivating layer. Films were characterized by transmission electron microscopy, x‐ray powder diffraction, and x‐ray photoelectron and Rutherford backscattering spectroscopies.

Electronic passivation of n‐ and p‐type GaAs using chemical vapor deposited GaS

We report on the electronic passivation of n‐ and p‐type GaAs using chemical vapor deposited cubic GaS. Au/GaS/GaAs fabricated metal‐insulator‐semiconductor (MIS) structures exhibit classical high‐frequency capacitor versus voltage (C‐V) behavior with well‐defined accumulation and inversion regions. Using high‐ and low‐frequency C‐V, the interface trap densities of ∼1011 eV−1 cm−2 on both n‐ and p‐type GaAs are determined. The electronic condition of GaS/GaAs interface did not show any deterioration after a six week time period.

Sterically crowded aryloxide compounds of aluminum

Abstract The chemistry of aluminum compounds containing sterically demanding aryloxide ligands is presented. In particular, those of compounds derived from 2,6-di-tert-butyl-4-methylphenol (BHT-H, from the trivial name butylated hydroxytoluene). The synthesis and structure of three-coordinate monomeric derivatives, and their ligand exchange reactions, are discussed in comparison to the more typical four-coordinate oligomeric aluminum alkoxide and aryloxide compounds. The reactions of the sterically crowded aryloxide compounds is divided into four general classes: oxidation and hydrolysis, the formation of Lewis acid-base complexes, the reaction with organic carbonyls, and the reaction with main group halides. Alane-aryloxide compounds are discussed separately, as are the 1,3-diphenyltriazenide derivatives. Finally, a discussion of the AlO bonding interactions in four-coordinate aluminum aryloxides is presented, giving spectroscopic and theoretical evidence for and against various postulates to explain the presence of short Al-O distances and large AlOC angles.

Indium tert-butylthiolates as single source precursors for indium sulfide thin films: Is molecular design enough?

Abstract The dimeric indium thiolates [R2In(μ-StBu)]2 R  tBu (1), nBu (2), Me (3), and [(tBuS)MeIn(μ-St Bu)]2 (4) have been synthesized and used as single source precursors for the metal-organic chemical vapor deposition (MOCVD) of In/InS and InS thin films. In the case of the atmospheric pressure film grown from either 1 or 2, deposition at temperatures between 290 and 350°C results in the formation of indium rich films (In: S ∼ 2) consisting of indium metal and orthorhombic InS, while at 400°C a single phase; the tetragonal high pressure phase of InS, is the only product deposited. Use of compound 3 as the precursor results in amorphous indium rich films being deposited at 300°C. While films grown from 3 at 400°C have a In: S ratio of 1, they consist of an indium rich phase and In2S3. The dependence of the film composition i.e., indium rich versus stoichiometric InS and structure (orthorhombic versus tetrag onal InS) with the deposition temperature and molecular precursor is discussed with respect to the decomposition pathways available to the precursor molecules (1–3). Based on these results compound 4 was proposed to be a suitable precursor for the low temperature deposition of stoichiometric InS, indeed its solid state pyrolysis does yield InS. However, although low pressure MOCVD using 4 yields amorphous films of stoichiometry InS, upon annealing β-In2S3 is formed as the crystalline phase. The efficacy of molecular design of solid state materials is discussed. The indium thiolates were characterized by 1H and 13C NMR spectroscopy and mass spectrometry. Analysis of the deposited films has been obtained by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), with associated energy dispersive X-ray analysis (EDX).

Isolation of the first gallium hydrosulphido complex and its facile conversion to a Ga4S4cubane: X-ray structures of [(But)2Ga(µ-SH)]2and [(ButGaS]4

The reaction of (But)3Ga with an excess of H2S in pentane at ambient temperature results in the formation of the hydrosulphido bridged dimer [(But)2Ga(µ-SH)]2, 1, which upon mild thermolysis is converted to the cubic tetramer [(But)GaS]42. Compounds 1 and 2 have been characterized by IR, NMR and mass spectroscopy and their molecular structures have been determined by X-ray crystallography.

Acylation and esterification of the aryloxide ligand in [AIMe(dbmp)2]. Crystal structures of [AIMe(dbmp)-(bhmap)], Hbhmap and OC(dbmp)But(Hdbmp = 2,6-di-tert-butyl-4-methylphenol, Hbhmap = 3-tert-butyl-2-hydroxy-5-methylacetophenone)

The reaction of [AIMe(dbmp)2](Hdbmp = 2,6-di-tert-butyl-4-methylphenol) with OC(Cl)Me leads to acylation of one of the dbmp ligands and affords [AIMe(dbmp)(bhmap)]1(Hbhmap = 3-tert-butyl-2-hydroxy-5-methylacetophenone). Hydrolysis of 1 yields uncomplexed Hbhmap 5. The Et, Pri and Ph analogues of 1 and 5 have been obtained by the use of the appropriate acyl chloride. By contrast, the interaction of [AIMe(dbmp)2] with OC(Cl)But results in the formation of OC(dbmp)But12 and [AlCl2(dbmp){OC(Me)But}]13. The molecular structures of 1, 5 and 12 have been confirmed by X-ray crystallography.

Organoaluminum promoted conversion of aldehydes to methyl ketones

Abstract The conversion of aromatic aldehydes to the corresponding methyl ketones has been accomplished with the use of the organo-aluminum aryloxide compound, AlMe2(BHT)(OEt2).

Sterically crowded aryloxide compounds of aluminium—reactivity of coordinated benzaldehyde

Abstract The interaction of aluminium complexes containing the sterically hindered phenoxide ligand 2,6-di-tert-butyl-4-methylphenoxide (BHT) with benzaldehyde has been investigated. Interaction of benzaldehyde with AlR(BHT)2 leads to the Lewis acid-base adduct AlMe(BHT)2[OC(H)Ph], R = Me. When R = Et, reduction of coordinated benzaldehyde is observed. The addition of benzaldehyde to AlMe2(BHT) leads to the formation of the acetophenone complex, AlMe2(BHT)[OC(Me)Ph]. A mechanism for this unique aldehyde to ketone transformation is proposed. The dimeric compound [AlEt(BHT)(OCH2Ph)]2 is formed from the interaction of AlEt2(BHT) and benzaldehyde.

Sterically Crowded Aryloxide Compounds of Aluminum: Complexes with Diethyl Ether and Tetrahydrofuran

Abstract The Et2O and THF Lewis acid-base adducts of AIR(BHT)2 and AIR2(BHT) [R = Me, Et; BHT-H = 2,6-di-tert-butyl-4-methyIphenol], have been prepared and characterized by elemental analyses, 1H and 13C NMR spectroscopy.