Richard L. Wells

The use of silylarsines to prepare gallium-arsenic compounds

A. Introduction B. Preparations of silylarsines C. Reactions of (Me,SiCH,),AsSiMe, and Mes,AsSiMe, (Mes = mesityl) ..... D. Reactions of Me,SiCH,As(SiMe,), and (Me3Si),As(CH2)3As(SiMe,), ..... E. Reactions of As(SiMe3)3. F. Concluding comments. Acknowledgements References 273 275 276 281 282 288 288 290

Synthesis and crystal structure of the dimer bis {[bis(trimethylsilylmethyl) arsino] diphenylgallane}

Abstract The dimer [(Me 3 SiCH 2 ) 2 AsGaPh 2 ] 2 , obtained from the reaction of (Me 3 SiCH 2 ) 2 AsH with Ph 3 Ga, has been characterized by partial elemental analysis, NMR spectroscopy, cryoscopic molecular weight determination, and complete single-crystal X-ray analysis. Crystals of the dimer are triclinic, space group P 1 , with a 10.541(1), b 11.939(1), c 10.539(1) A, α 99.72(1), β 83.00(1), γ 114.55(1)°, U 1187.1 A 3 and Z = 1. The bond lenghts (GaAs 2.518(1) and GaAs′ 2.530(1) A) and bond angles (AsGaAs′ 85.08(2) and GaAsGa′ 94.92(2)°) in the centrosymmetric, and consequently planar, four-membered ring indicate a significant degree of strain.

Synthesis and crystal structure of tris(dimesitylarsino)gallane, a monomeric tricoordinate gallium-arsenic compound

Abstract : The gallium-arsenic bond, in polymeric form is expected to exhibit anisotropic conductivity by virtue of an extended p-pi system, isoelectronic with polyacetylene. Four mono-, bis-, and trisarsinogallanes were prepared from the reaction of lithium dimesitylarsenide with gallium chlorides. One of these, tris(dimesitylarsino) gallane, (Mes2As)3Ga(1), was characterized by single crystal x-ray analysis and shown to be the first example of a monomeric tricoordinate gallium-arsenic compound. Orange crystals of 1 belong to the triclinic system space group P1. The gallium atom is bonded to the three arsenic atoms in a trigonal planar configuration. The color of 1 is the result of tailing of a 276 nm CT band into the visible.

Pathways to Nanocrystalline III-V (13-15) Compound Semiconductors.

Discussed in this review are various solution-phase methodologies and specific chemical reactions involving molecular precursors and/or species derived there-from which have been utilized to synthesize various binary and ternary nanocrystalline III-V (13–15) compound semiconductors.

Preparation of single-source precursors to nanocrystalline gallium arsenide and gallium antimonide. X-ray crystal structures of [Et2GaAs(SiMe3)2]2, [Et2GaSb(SiMe3)2]2 and Et2b(SiMe3)2 ☆

Abstract The 1:1 mole ratio reaction of Et2GaCl with As(SiMe3)3 leads to the isolation of [Et2GaAs(SiMe3)2]2 (1), while the analogous reaction with Sb(SiMe3)3 results in the formation of [Et2GaSb(SiMe3)2]2 (2). The mixed-pnicogen compound Et2 GaAs(SiMe 3 ) 2 Ga(Et) 2 S b(SiMe3)2 (3) was obtained from both the equilibration of 1 and 2, as well as the 2:1:1 mole ratio reaction of Et2GaCl with As(SiMe3)3 and Sb(SiMe3)3. X-ray crystal structures are reported for 1, 2 and 3, as well as a variable temperature 1H-NMR study of 2 and 3. The dimer 2 was found to exhibit a dimer/trimer equilibrium in solution. Thermolysis of all three compounds results in the formation of GaAs, GaSb or GaAsxSb(1−x) through a β-hydride elimination pathway.

Preparation of Phase Pure Cubic Gallium Nitride, c-GaN, by Ammonothermal Conversion of Gallium Imide, {Ga(NH)3/2}n

Gallium imide, {Ga(NH)3/2}n, was sealed in quartz tubes with anhydrous NH3 and NH4X (X=Cl, Br, I) and heated vertically in an autoclave with the hot-zone (bottom) temperature ranging from 300–530°C. With NH4I mineralizer, the imide was converted to primarily the zinc-blende phase of GaN (c-GaN), usually in the form of micron sized or smaller tetrahedra. With NH4Cl mineralizer, hexagonal GaN nanoparticles formed instead, and NH4Br facilitated the conversion of imide to irregular h-GaN nanoparticles at lower temperatures, and larger particles above 500°C. At the higher temperatures, chemical transport took place and GaN crystals grew on the walls at the middle to the top of the tube. Most of the deposited GaN was cubic, usually in a heavily etched triangular prismatic morphology. Several experiments were performed in a Pt lined pressure vessel in order to demonstrate that the synthesis method can be scaled up.

Synthesis and characterization of single-source precursors to nanocrystalline GaP, GaPxAs1−x, and GaPxSb1−x. X-ray crystal structures of [Et2GaP(SiMe3)2]2, (Me3Si)2P[μ-GaEt2]2As(SiMe3)2, and (Me3Si)2P[μ-GaEt2]2Sb(SiMe3)2

The 1:1 mole ratio reaction of Et 2 GaCl with P(SiMe 3 ) 3 resulted in the formation of [Et 2 GaP(SiMe 3 ) 2 ] 2 ( 1 ). The mixed-pnicogen compounds (Me 3 Si) 2 P[μ-GaEt 2 ] 2 As(SiMe 3 ) 2 ( 2 ) and (Me 3 Si) 2 P[μ-GaEt 2 ] 2 Sb(SiMe 3 ) 2 ( 3 ) were prepared from the 2:1:1 mole ratio reactions of Et 2 GaCl with P(SiMe 3 ) 3 and As(SiMe 3 ) 3 and P(SiMe 3 ) 3 and Sb(SiMe 3 ) 3 , respectively. Compounds 2 and 3 were also synthesized by comproportionation reactions of 1 and [Et 2 GaAs(SiMe 3 ) 2 ] 2 , and 1 and [Et 2 GaSb(SiMe 3 ) 2 ] 2 , respectively. Characterization of 1 , 2 , and 3 was accomplished using multinuclear NMR, elemental analysis, mass spectrometry, and single-crystal X-ray crystallographic analysis. The X-ray crystal structures of compounds 1 , 2 and 3 are reported. Thermolysis of 1 , 2 , and 3 results in the formation of nanocrystalline GaP, GaP x As 1− x , or GaP x Sb 1− x , respectively. Compound 3 represents the first example of a compound containing a P(μ-Ga) 2 Sb core.

Preparation and Chemistry of Me3SiCH2AsH2; Preparation of (Me3SiCH2(H)AsGaPh2)3, A Trimeric Mono(Arsino)Gallane Containing a Hydrogen Bonded to Arsenic. Isolation and X-Ray Crystal Structure of (Me3SiCH2As)5

Abstract Reduction of Me3SiCH2AsCl2 (I) with LiA1H4 at −78°C afforded Me3SiCH2 AsH2 (II) and reaction of II with Ph3Ga produced [Me3SiCH2(H)AsGaPh2]3 (III) which was characterized by partial elemental analysis (C and H), 1H NMR spectroscopy and a cryoscopic molecular weight determination. Based on 1H NMR data, [Me3SiCH2 (H)AsGaMe2]3 (IV) was produced by the reaction of II with Me3Ga; however, only H2, Me4Si, (Me3SiCH2As)5 (VI) and unreacted (Me3SiCH2)3Ga were identified after allowing the latter to react with II. Reaction of 2 equiv. of Me3SiCl with a mixture of II and n-BuLi (1 : 2 mole ratio) afforded Me3SiCH2As(SiMe3)2 (V). The monosilylated arsine was not isolated when 1 equiv. of Me3SiCl was allowed to react with combined II and n-BuLi (1 : 1 mole ratio); rather, a mixture of II and V resulted. Attempted preparations of (Me3SiCH2AsGaPh)n, are described. The ring compound, VI, was prepared by reaction of I with a mixture of Me3SiCl and Mg in THF. The molecular structure of this cycloarsane was determined by single-crystal X-ray diffraction methods. Pale yellow crystals of VI belong to the monoclinic system with four molecules occupying the general positions of space group P21/c(C2h5)with cell constants: a = 9.952(1), b = 30.245(9), c = 13.000(3) A, β = 91.69(1)°, V = 3911.3 A 3, Z = 4.

Synthesis and characterization of a dimeric tris(arsino)gallane containing a nonplanar (Ga-As)2 ring: crystal structure of {[(Me3SiCH2)2As]3Ga}2

Abstract The dimer {[(Me 3 SiCH 2 ) 2 As] 3 Ga} 2 , only the second tris(arsino)gallane to be completely characterized, has been prepared by the reaction of (Me 3 SiCH 2 ) 2 AsLi with GaCl 3 ; X-ray crystallographic analysis shows it to be the first example of a compound containing a distinctly nonplanar four-membered ring of alternating four-coordinate Ga and As atoms.

Synthesis and characterization of four-membered gallium-arsenic ring compounds containing a bridging As(SiMe3)2 group: crystal structures of Ph2GaAs(SiMe3)2Ga(Ph)2Cl and Ph2GaAs(SiMe3)2Ga(Ph)2Br

Abstract The first organogallium four-membered ring compounds with arsenic, halogen mixed bridging to be characterized completely, Ph 2 GaAs(SiMe 3 ) 2 Ga(Ph) 2 X (X = Cl ( 1 ) and X = Br ( 2 )) were prepared by the reaction of (Me 3 Si) 3 As ( 3 ) with Ph 2 GaCl and Ph 2 GaBr, respectively. X-ray crystallographic analyses show the compounds to be isostructural with each containing a non-planar Ga-As-Ga-X four membered ring. Isomorphous crystals of 1 and 2 belong to the monoclinic system, space group P 2 1 / c ( C 5 2 h ), with four molecules in unit cells of dimensions: a 10.560(3), b 15.797(3), c 20.591(4) A, β 92.17(2)°, V 3433(2) A 3 for 1 , and a 10.653(1), b 15.777(2), c 20.517(2) A, β 91.97(1)°, V 3446(1) A 3 for 2 . The non-planarity of the rings is manifested in the halogen atom displacements of 0.256 A in 1 and 0.293 A in 2 from the respective Ga-As-Ga′ planes. Deviations from overall C 2 v symmetry serve to relieve unfavorable intramolecular bulky ring substituent interactions present in such a symmetric form. The dimer [Ph 2 GaAs(SiMe 3 ) 2 ] 2 ( 4 ), obtained from the reaction of Ph 2 GaCl and LiAs(SiMe 3 ) 2 , has been characterized by partial elemental analysis, NMR spectroscopy and cryoscopic molecular weight determination. An alternative route to the synthesis of 1 by reaction of 4 and Ph 2 GaCl was investigated via NMR spectroscopy.