X-ray Structural Analysis for the Prediction on the Nature of the Retro Diels - Alder Pathway: Concerted or Stepwise. Structural Studies on Nitrosobenzene Cycloadducts

2009 ◽  
Vol 62 (12) ◽  
pp. 1695 ◽  
Author(s):  
Jesse Roth-Barton ◽  
Jonathan M. White
Keyword(s):  
Structural Analysis ◽  
Crystal Structures ◽  
Diels Alder ◽  
Structure Parameters ◽  
Structural Studies ◽  
Structural Effects ◽  
X Ray ◽  
Early Stages ◽  
Clear Differentiation

Crystal structures of nitrosobenzene cycloadducts 5–7 reveal structural effects consistent with the early stages of the retro Diels–Alder fragmentation. There is a clear differentiation between the structure parameters of cycloadduct 5, which reacts by a concerted synchronous pathway and that of cycloadduct 6, which must react by a two-step pathway. Based on these data, cycloadduct 7 is predicted to react by a highly asynchronous or two-step pathway.

X-Ray Structural Analysis of Ester and Ether Derivatives of 4,5-endo,endo-9,10-Dimethanonaphthalene-11-ol: Evidence for π - σCO* Participation in the Ground State

2008 ◽  
Vol 61 (12) ◽  
pp. 956 ◽  
Author(s):  
Wesley Jackson ◽  
Jonathan M. White
Keyword(s):  
Structural Analysis ◽  
Weak Interaction ◽  
Ground State ◽  
System Analysis ◽  
Diels Alder ◽  
Oxygen Probe ◽  
Structural Effects ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Derivatives Of

Application of the variable oxygen probe to the polycyclic alcohol 11 and its crystalline ester and ether derivatives provides evidence for a weak interaction between the neighbouring homo-allylic π-system and the C–OR bond; there is no evidence for interaction with the remote π-system. Analysis of the carbon–carbon bond distances in 11–14 reveals structural effects consistent with the manifestation of one of the two possible retro-Diels–Alder reactions in the ground state.

Comparative Structural Studies on Three-Coordinate Copper(I) Halide Complexes With Tertiary Phosphines. Crystal Structures of [(PPh2Mes)CuX]2 and [(PPhMes2)CuX]2 (Mes = Mesityl X = Cl, Br, I)

1992 ◽  
Vol 45 (7) ◽  
pp. 1155 ◽  
Author(s):  
GA Bowmaker ◽  
D Camp ◽  
RD Hart ◽  
PC Healy ◽  
BW Skelton ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Copper Atom ◽  
Structural Studies ◽  
Coordination Environment ◽  
X Ray ◽  
Tertiary Phosphines ◽  
Structure Determinations ◽  
Halide Complexes ◽  
The Subject

The 1 : 1 complexes of the substituted triphenylphosphine ligands mesityldiphenylphosphine and dimesitylphenylphosphine with copper(1) chloride, bromide and iodide have been the subject of single-crystal X-ray structure determinations at 295 K. All six complexes crystallize as air-stable dimeric molecules, [(PPh2Mes)CuX]2 and [ (PPhMes2)CUX]2 with each copper atom in a distorted trigonal PCuX2. coordination environment. Crystals of [(PPh2Mes)CuCl]2 (1) are monoclinic, P21/n, a 9.961(3), b 18.687(6), c 11.009(7) Ǻ, β 114.63(4)°; R was 0.049 for 2450 'observed' reflections. [(PPh2Mes)CuBrI2 (2) is monoclinic, P21/n, a 9.939(2), b 18.832(6), c 11.238(6) Ǻ, β 115.36(3)°; R was 0.046 for 1803 'observed' reflections. [(PPh2Mes)CuI]2.4/3 C6H6 (3) is rhornbohedral, R3, a 36.877(8), c 9.047(5) A; R was 0.039 for 2537 'observed' reflections. Crystals of [(PPhMes2)CuCl]2.2MeCN (4) are triclinic, Pi, a 15.783(7), b 9.570(4), c 8.914(4) Ǻ, α 72.43(3), β 76.37(3), γ 74.03(3)°; R was 0.045 for 3341 'observed' reflections. [(PPhMes2)CuBr]2.3C6H6 (5) is monoclinic, C2/c, a 9.694(6), b 30.15(2), c 20.66(2) Ǻ, β 98.00(7)°; R was 0.047 for 2117 'observed' reflections. [(PPhMes2)CuI]2.2MeCN (6) is orthorhombic, PP1nb, a 11.694(8), b 14.77(1), c 29.76(3) Ǻ; R was 0.049 for 3447 'observed' reflections. Cu-P bond lengths are: 2.196(2) A (1); 2.198(3) Ǻ (2); 2.222(5) and 2.226(5) Ǻ (3); 2.202(1) Ǻ (4); 2.197(3) A (5); 2.201(4) and 2.264(5) Ǻ (6). The geometries of the LCuX2 and CuX2Cu units are compared with data reported for other monomeric and dimeric compounds for both phosphorus- and nitrogen-based ligands L.

Structural Studies of Some o- and p-Nitrophenylcarbamates by IR Spectroscopy and X-Ray Diffraction

2008 ◽  
Vol 63 (12) ◽  
pp. 1402-1406
Author(s):  
Monika Simon ◽  
Carol Csunderlik ◽  
G. Jones
Keyword(s):  
Ir Spectroscopy ◽  
Crystal Structures ◽  
Ir Spectrum ◽  
Structural Studies ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray

N-Alkyl-o-nitrophenylcarbamates as solids present two carbonyl stretching bands in the region 1700 - 1800 cm−1 but similar N-alkyl-p-nitrophenylcarbamates have only one such band in the IR spectrum. In solution both kinds of carbamate present one carbonyl stretching band, but for the former, the splittings occur when the carbamates crystallize. Four crystal structures were analyzed by X-ray diffraction. The two ortho derivatives have more than one molecule in the asymmetric unit, which is consistent with the IR observations.

Influence of Trimethylsilyl Substituents on Primary C - O Bond Lengths at the b-Position: Results from Low-Temperature X-Ray Structural Studies

1997 ◽  
Vol 50 (9) ◽  
pp. 927 ◽  
Author(s):  
Alison J. Green ◽  
William Issa ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Ester Bond ◽  
Structural Studies ◽  
Structural Effects ◽  
X Ray ◽  
Bond Lengths

The β-trimethylsilyl substituent in 2-trimethylsilylethyl p-nitrobenzoate (12b) and 2-trimethylsilylethyl 2,4-dinitrobenzenesulfenate (12c) leads to significant lengthening of the C(alkyl)–O(ester) bond. Lengthening of the Si-CH2 distance in the more electronegative ester (12c) relative to (12b) is also observed. These structural effects are consistent with the presence of σC-Si–σ* C-O interactions.

Darstellung und Kristallstrukturen von Phenyliodoantimonaten(III). Strukturkorrelation für Halogenoantimonate(III) / Preparation and Crystal Structures of Phenyliodoantimonates(III). Structural Correlation for Haloantimonates(III)

1991 ◽  
Vol 46 (5) ◽  
pp. 639-646 ◽  
Author(s):  
W. S. Sheldrick ◽  
C. Martin
Keyword(s):  
Structural Analysis ◽  
Crystal Structures ◽  
Iodine Atom ◽  
Trans Position ◽  
X Ray ◽  
Trigonal Bipyramidal ◽  
Structural Correlation ◽  
Bipyramidal Structure ◽  
In Trans

The phenyliodoantimonates(III) [Et4N][Ph2SbI2] (1), [Et4N]2[Ph2Sb2I6] (2) and [Hpy]3[Ph2Sb2I7] (3) have been prepared and their structures established by X-ray structural analysis. The anion [Ph2SbI2]⁻ displays a ψ-trigonal bipyramidal structure with axial Sb–I distances of 2.925(1) and 3.109(1) A. In the dimeric anions [Ph2Sb2I6]2- and [Ph2Sb2I7]3- the antimony atoms exhibit ψ-octahedral geometries. As observed for [Ph2SbI2]⁻, terminal Sb–I bonds in trans-position to one another display significantly different lengths. The anion [Ph2Sb2I7]3- displays Ci- symmetry with a bridging iodine atom at the crystallographic centre of symmetry. Long Sb—I distances of 3.404(1) A are observed to this atom. A structural correlation of opposite Sb–X distances (X = Cl, Br, I) in linear three centre X–Sb ··· X interactions is presented. The sum of the bond valences in iodoantimonates(III) is a minimum for symmetrical I–Sb–I three centre bonds, reflecting thereby the antibonding influence of the Sb 5 s-orbital. This influence is considerably smaller for bromoantimonates(III) and may be effectively neglected for chloroantimonates(III).

Structural Studies of N-Acyl 1,1′-Bis(1,2,3,4-tetrahydroisoquinoline) Derivatives

2002 ◽  
Vol 55 (11) ◽  
pp. 733 ◽  
Author(s):  
Donald C. Craig ◽  
Zaher M. A. Judeh ◽  
Roger W. Read
Keyword(s):  
Crystal Structures ◽  
Structural Studies ◽  
X Ray ◽  
Solid States ◽  
First Time ◽  
Rotational Freedom

The X-ray crystal structures of N-acyl substituted 1,1′-bis(1,2,3,4-tetrahydroisoquinolines) are disclosed for the first time and evidence is provided that the molecules reside in single preferred conformations in solution and solid states, with axial bonds bridging C1–C1′ that have no steric impediment to rotational freedom.

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