Yongkwan Dong

New synthesis and ring opening of cis-3-alkylaziridine-2-carboxylates

Abstract Syntheses of cis-3-alkylaziridine-2-carboxylates including cis-3-benzyl- and cis-3-phenylaziridine-2-carboxylates were achieved from the reaction of α-aminonitrile and alkyldiazoacetate in the presence of a Lewis acid. Asymmetric version of this reaction with the chiral α-methylbenzylamine was also successful for the preparation of chiral aziridines that were used for the synthesis of various amino acids including homophenylalanine, β-amino-α-hydroxy acid, α,β-diamino acid, and α-amino-β-hydroxy acid via regioselective aziridine ring openings.

Di­cyano{[(1S)-(1-phenyl­ethyl)­aziridin-2-yl]­methano­lato-κ2N,O}boron

In the title compound, C 13 H 14 BN 3 O, the aziridine ring is an almost equilateral triangle, the C-C distance being slightly shorter than the C-N distances, probably because of the dative B-N bond. The five-membered ring, composed of two C atoms and N, B and O atoms, is fused with the aziridine ring to form a six-membered ring with a chair conformation.

A new thiophosphate, Rb0.38Ag0.5Nb2PS10

The structure of the new pentanary thiophosphate rubidium silver diniobium tris(disulfide) tetrathiophosphate, Rb(0.38)Ag(0.5)Nb2PS10, is made up of one-dimensional (infinity)1[Nb2PS10-] chains along the [001] direction. These chains are separated from one another by Ag+ and disordered Rb+ ions. The Nb2PS10- chain is built up from bicapped trigonal prismatic Nb(2)S(12) units which lie about inversion centres and tetrahedral PS4 groups. The Nb2S12 units are linked together to form linear Nb2S9 chains by sharing S-S prism edges. Short [2.898 (1) and 2.908 (1) A] and long [3.724 (1) A] Nb...Nb distances alternate along the chains, and S(2)2- and S2- anionic species co-exist in the structure. The Ag(+) cation lies on an inversion centre and has distorted octahedral coordination described as a [2+4]-bonding interaction.

A comparative study on structures and theoretical models of Rh azido complexes

The syntheses of PF 6 − salt of six-coordinate Rh(III) azido complexes containing polypyridyl ligands have been accomplished by treatment of the corresponding Rh(III) chloride with NaN 3 in EtOH–H 2 O followed by the addition of NH 4 PF 6 . The complexes have been characterized by UV–vis, FTIR, 1 H and 14 N-NMR spectroscopy along with elemental analysis. The X-ray crystal structures of compounds [Rh(tpy)(phen)(N 3 )](PF 6 ) 2 ( 1 ·(PF 6 ) 2 , tpy: 2,2′:6′,2″-terpyridine, phen: 1,10-phenanthroline) and [Rh(tpy)(bpy)(N 3 )](PF 6 ) 2 ( 2 ·(PF 6 ) 2 , bpy: 2,2′-bipyridine) confirm that a rhodium atom is six-coordinate and the tpy and bpy or phen ligands are orthogonal and the RhN 3 distances are 2.038(7) and 2.048(6) A, respectively. The two NN distances for the coordinated azide in complex 1 ·(PF 6 ) 2 are identical with distances of 1.17 (1) and 1.17 (1) A. However, the two NN distances for the azido group in the complex 2 may or may not be inequivalent with 1.170(8) and 1.15(1) A. The bond angles formed by the azide group, Rh, and the axially-positioned nitrogen atom are 172.1(3) and 173.5(8)°. In order to answer the question as to whether the two NN distances in 2 would be expected to be different, calculations were carried out at HF/LANL2DZ and HF/SDD levels of theory. The results indeed predict the NN distances in 2 to be different.

MOCVD of Aluminum Nitride Thin Films with a New Type of Single-Source Precursor: AlCl3:tBuNH2

A new type of precursor, AlCl 3 : t BuNH 2 adduct, has been designed. The synthesis, preparation, and characterization of AlN thin films have been carried out. The AlCl 3 : t BuNH 2 adduct was a stable solid material with high vapor pressure (2.5 torr at 65 °C) which was purified by sublimation. The structure of the precursor was fully identified by an X-ray single crystal analysis, elemental analysis, and nuclear magnetic resonance (NMR). The CVD process was performed using hydrogen under atmospheric pressure as the carrier gas. The film was characterized by Rutherford backscattering spectroscopy (RBS), Auger electron spectroscopy (AES), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The quality of the film prepared from the precursor was excellent, with a preferential c-axis orientation, exceptionally low carbon contamination, and an ideal N/Al atomic ratio.

The Sol-Gel Chemistry of Ferroelectric SrBi2Ta2O9 Thin Layers

A characterization of sol-gel precursors of SrBi2Ta2O9 (SBT) has been carried out. Each molecular precursor, [SrBi2+xTa2(OCH2CH2OCH3)18]n (1) (x = 0.0, 0.2, and 0.4) and [SrTa2(OEt)(OiPr)11(iPrOH)2] (2) was prepared from the mixtures of Bi(OR)3, Sr(OR)2, and Ta(OR)5 (R = Et, iPr, and CH2CH2OCH3), respectively. 1H and 13C NMR spectroscopy and powder X-ray diffractometry have been used to characterize precursor molecules and their oxides, respectively. Especially, X-ray single crystal studies of complex 2 show that the molecule is made up of three octahedra; the central [SrO6] octahedron is sharing two neighboring edges with the peripheral [TaO6] ones. The SBT film derived from the precursor 1 presents outstanding ferroelectric properties (Pr = 9 μC/cm2; Ec = 0.8 V).

Reinvestigation of Hg2GeSe4 based on single-crystal data

Dimercury(II) germanium(IV) tetraselenide, Hg2GeSe4, adopts a cation-deficient diamond-like structure. It crystallizes in space group I\overline 4 of the tetragonal system. The structure consists of tetrahedral [HgSe4] and [GeSe4] groups. These groups are interconnected by sharing common corners. The previous structure report on Hg2GeSe4 based on powder diffraction data [Parasyuk et al., (2003). J. Alloys Compd, 351, 135–144] is comparable with our results except for the absolute configuration determination. In the asymmetric unit, the site symmetries of the Hg and Ge atoms are \overline 4.

Structural Characterization Of Rh(Iii) Complexes Containing The Polypyridyl Ligands And Some Properties Of Their Derivatives

The structures of the compounds [Rh(bpy)2(py)(Cl)](ClO4 )2 (2 (ClO4 )2) and [Rh(phen)2(py)- (Cl)](ClO4 )2 (7 -(ClO4 )2) were determined by single-crystal X-ray diffraction. Both complexes show a six-coordinate rhodium atom with two bpy or phen ligands in the cis configuration. The Rh-Cl distances are 2.334(3) and 2.323(2) Å, respectively. The bond angles N-Rh-Cl formed with the axially-positioned nitrogen atom are 174.4(2) and 173.8(2)°. The oxidation of aquo complexes, prepared from the corresponding rhodium chloride complexes, by two equivalents of Ce(IV) in 60% HCIO4 solution yields the corresponding mono-oxo products. All complexes have been identified and characterized by elemental analyses, IR, and 1H NMR data