Duane C. Hrncir

Steric effects on the optical and electrochemical properties of N-substituted pyrrole–thiophene monomers and polymers

Monomers consisting of N-alkyl-substituted-2,5-bis(2-thienyl)pyrroles and thier electro-oxidatively generated polymers display electrochemical and optical properties which reflect the steric demands of the alkyl substituents.

Reduction of steric interactions in thiophene-pyridino[c]thiophene copolymers

An electroactive polymer with an energy gap of 1.4 eV has been obtained from the monomer 2,5-di(2-thienyl)pyridino[c]thiophene.

Organoaluminum-phosphine chemistry. Synthesis and molecular structure of [Ph2P(O)2 · AlCl2]2 and [Ph2P · Al(i-Bu)2]2

The crystalline complex [Ph2P(O)2 · AlCl2]2 (I) was prepared by reaction of the disproportionation product of ethylaluminum sesquichloride, EtAlCl2, or by direct reaction of EtAlCl2 with diphenylphosphonic acid, Ph2P(O)OH, in a heptane/toluene mixture. I crystallizes in the monoclinic space group C2/c with unit cell parameters a 11.201(9), b 15.059(6), c 17.665(5) A, β 105.4°(2), V 2979.7 A3 and Dcalc 1.40 g cm−3 for Z = 4. Least-squares refinement based on 1656 observed reflections led to a final R factor of 0.047 (R2 = 0.062). I resides about a crystallographic center of symmetry. The core of the dimer consists of a planar eight-membered (Al-O-P-O)2 ring. The mean Al-O bond distance is 1.73(1) A while the independent Al-Cl bond distance is 2.085(2) A. The organoaluminum crystalline product [Ph2P · Al(i-Bu)2]2 (II) was prepared by reaction of diisobutylaluminum hydride with diphenylphosphine in heptane. II crystallizes in the orthorhombic space group Pbca with unit cell parameters a 12.809(2), b 15.207(2), c 20.574(3) A, V 4008.5 A3, and Dcalc 1.08 g cm−3 for Z = 4. Least-squares refinement based on 2111 observed reflections converged at R = 0.036, Rw = 0.049. The dimeric organoaluminium compound possesses crystallographic inversion symmetry and contains a planar four-membered Al2P2 ring. The mean Al-P bond distance is 2.476(1) A. The Al-P-Al bond angle in the Al2P2 ring is 93.8(1)° while the P-Al-P bond angle is determined to be 86.2(1)°. The Al ··· Al and P ··· P contact distances are 3.615(1) A and 3.381(1) A, respectively.

Synthesis and structural characterization of (Ph3SiOH)2·12-c-4. A model for chemistry occurring at the sediment–water interface in natural waters

The first hydrogen bonded adduct formed from an organosilanol and a crown ether has been synthesized, structurally characterized, and compared to species found in natural aquatic systems.

Alkylsilazalanes. Reaction of trimethylaluminium with silazanes: Synthesis and molecular structure of [Al(CH3)2]2[C12H32N2Si4] and [Al(CH3)2]2[C8H28N2Si4]

The crystalline product [Al(CH 3 ) 2 ] 2 [C 12 H 32 N 2 Si 4 ] ( I ), obtained from reaction of 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentane with trimethylaluminium in a heptane-chlorobenzene mixture, crystallizes in the orthorhombic space group Pbca (No. 61) with unit-cell parameters a = 15.393(3), b = 12.987(2), c = 13.189(4) A, V = 2637.4(2) A 3 and D c = 1.06 g cm −3 for Z = 4. Full-matrix least-squares refinement based on 1549 observed reflections with intensities in the range 4.00 R = 0.048 ( R w = 0.064). Compound I resides about a crystallographic centre of symmetry and contains a planar Al 2 N 2 four-membered ring with an Al⋯Al contact of 2.790(3) A. Reaction of trimethylaluminium with 1,1,3,3-tetramethyldisilazane in heptane affords the crystalline product [Al(CH 3 ) 2 ] 2 [C 8 H 28 N 2 Si 4 ] ( II ). Compound II crystallizes in the triclinic space group P (No. 2) with unit-cell parameters a = 9.354(2), b = 14.670(3), c = 17.536(4) A, α = 91.24(2), β = 90.63(2), γ = 99.46(2)°, V = 2372.7(9) A 3 and D c = 1.06 g cm −3 for Z = 4. Full-matrix least-squares refinement based upon 5033 observed reflections with intensities in the range 3.50 R = 0.035 ( R w = 0.048). The mean Al ⋯ Al contact across the Al 2 N 2 four-membered ring in II is 2.813(1) A. The mean AlN bond distance in I is 2.005(3) A while the mean AlN bond distance in II is 1.992(3) A.

Indium-based liquid clathrates. II. Inclusion compounds derived from salts of the tetrachloroindate anion, InCl 4 ? , and the crystal structure of [Li15-c-5] [In(CH3)3Cl] (15-c-5=15-crown-5)

Indium(III) chloride reacts with 12-c-4 to give the 1:1 adduct [InCl3·12-c-4]. This complex is a convenient In precursor to liquid clathrates. [InCl3·12-c-4] reacts with LiCl to form [Li·12-c-4] [InCl4]. When the reaction is carried out in the presence of an aromatic solvent such as toluene, a liquid inclusion complex forms readily. It has been determined that the C6H5CH3:[Li·12-c-4] [InCl4] ratio is 2. Alkylation of the 15-c-5 adduct of InCl3 with methyllithium yields [Li·15-c-5] [In(CH3)3Cl]. The salt fails to form inclusion complexes with aromatic molecules. This compound has been characterized using single crystal X-ray diffraction. The molecule belongs to the monoclinic space groupP21/n, witha=7.515(2),b=18.952(6), andc=13.938(7) Å, β=95.12(3)° andDcalc=1.43 g cm−3 for Z=4. Least squares refinement based upon 2348 observed reflections led to a finalR=0.039.

GROUP 13 AMIDES. SYNTHESES AND MOLECULAR STRUCTURES OF [(i-Bu)2Al-N(H)Mes]2,[(i-Bu)Al-N(H)Ph(t-Bu)2-μ-(CMe2CH2)]2, [Me2In-N(H)Ph′]2, AND [(i-Bu)2Al-N(H)Ada]2

Abstract The sterically demanding Group 13 amide dimers [(i-Bu)2Al-N(H)Mes]2 (I), [(i-Bu)Al-N(H)Ph(t-Bu)2-μ-(CMe2CH2)]2 (II), [Me2In-N(H)Ph′]2 (III), and [(i-Bu)2Al-N(H)Ada]2 (IV) (Ada = adamantyl; Bu=butyl; Mes = Ph(Me)3; Ph = phenyl; Ph′= 2-biphenyl) have been prepared by reaction of (i-Bu)2AIH or Me3In with the respective primary amine and characterized by 1H NMR, elemental analyses, and single crystal X-ray diffraction. I crystallizes in the triclinic space group P1 with unit cell parameters a = 9.272(1), b = 9.718(2), c = 11.585(2)A, α = 101.76(1)°, β = 106.69(1)°, γ = 109.70(1)°, V=887.5(2)A3, and Dcalc = 1.03g cm−3 for Z = 1. Least-squares refinement based on 1644 observed reflections with intensities I > 3σ(I) in the range 3.5 < 2 < 45.0° converged at R = 0.043 and R w = 0.054. II crystallizes in the monoclinic space group P21/c with unit cell parameters a = 11.292(5), b = 17.544(9), c = 11.532(5)A, β = 107.99(4)°, V = 2173(2)A3, and Dcalc = 1.05 g cm−3 for Z = 2. Least-squares refinement based on...

Synthesis and structural characterization of [Ph2Si(OH)OSi(OH)Ph2]3·(C4H4N2)2. The first crystallographic evidence for silanol–amine hydrogen bonding and its implications for organic–sediment interactions in natural waters

The novel 3 : 2 adduct, [Ph2Si(OH)OSi(OH)Ph2]3·(C4H4N2), is bonded via silanol–amine hydrogen bonds which have been structurally characterized for the first time; it also contains two distinct geometries for the disiloxane molecules.

Preparation of heterosiloxanes containing Zr and Hf and their use as precursors to refractory materials

Metallasiloxanes of the type, M (OSiR 3 ) 4 , which contain zirconium and hafnium can be prepared by the facile silanol-induced cleavage of organometallic compounds. The metallasiloxanes vary from mobile liquids to insoluble nonmelting powders depending upon the constituents bonded to the silicon. The compounds can be fired into inorganic refractory oxides at temperatures varying from 350–600 °C. The resulting materials have the general formula M Si 4 O 10 . Electron spectroscopy for chemical analysis (ESCA) data suggest that the M -O–Si linkage remains intact during this process. Thus the M Si 4 O 10 material can be considered a mixed oxide alloy rather than a simple mixture of the oxides M O 2 and SiO 2 .

Indium-based liquid clathrates. I. The preparation of the first indium liquid inclusion compound and crystal structure of its parent complex, [K · 18-Crown-6]2[InClI2(CH3)][InClI(CH3)2]

The synthesis of the first liquid clathrate derived from an indium precursor is described. The aromatic/anion ratio of the inclusion complex prepared using benzene is 12.4. The use of toluene results in the inclusion of 10.3 guest toluene molecules/anion. The crystal structure of the parent complex, [K·18-Crown-6]2[InClI2(CH3)][InClI(CH3)2] was carried out. The compound belongs to the monoclinic space groupP21/c, witha=19.508(9),b=8.503(5), andc=29.437(9) Å, β=96.55(3)°, andDcalc=1.83 g cm−3 forZ=4. Least-squares refinement based on 3449 observed reflections led to a finalR=0.099. The structure displays two different environments for the two K+ cations in the asymmetric unit. One adopts the near-planar [K·18-crown-6]+ configuration while the other K+ resides 0.81 Å above the second 18-crown-6 plane. The latter K+ is apparently pulled out of the crown by a strong interaction with a Cl− ion.