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.

Probing the Ground-State δ Effect of Group 14 Metal Substituents. X-Ray Structures of cis- and trans-4-Trimethylmetal-Substituted Cyclohexyl p-Nitrobenzenesulfonates

1998 ◽  
Vol 51 (7) ◽  
pp. 555 ◽  
Author(s):  
Alison J. Green ◽  
Victor Van ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Ground State ◽  
Structural Studies ◽  
Structural Effects ◽  
Group 14 ◽  
X Ray ◽  
Bond Interaction ◽  
Cis And Trans

Accurate low-temperature X-ray structural studies on trans-4-trimethylsilylcyclohexyl p-nitrobenzene- sulfonate (31) and cis- and trans-4-trimethylstannylcyclohexyl p-nitrobenzenesulfonates (32) and (33) failed to demonstrate the presence of any significant structural effects due to a σM-C-σC-C-σ*C-O through-bond interaction between the C–M σ donor orbital and the σ*C-ONs acceptor orbital.

Improved Synthetic Route to Unsymmetrically Substituted Phosphinimino-phosphonium Salts. Crystal Structure of Tri-n-butyl- [tris(diethylamino)phosphinimino]phosphonium Chloride

2001 ◽  
Vol 56 (12) ◽  
pp. 1319-1321 ◽  
Author(s):  
R. Bartsch ◽  
M. Freytag ◽  
S. Goller ◽  
R G. Jones ◽  
R. Schmutzler
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Title Compound ◽  
Phosphonium Salts ◽  
Synthetic Route ◽  
X Ray ◽  
Bond Lengths ◽  
Phosphonium Chloride

Abstract The title compound was prepared from tri-n-butyl-chlorophosphonium chloride and N-tri-methylsilyl-tris(diethylamino)-phosphinimine. A low temperature X-ray crystal structure de­termination revealed PN bond lengths of 156.1(2) and 158.0(2) pm, with a PNP angle of 149.36(17)°.

Synthesis and Structural Studies of Tetrahedral [M(Ph2P(CH=CH)PPh2)2]BPh4 and [M(Ph2P(CH2)nPPh2)2]BPh4 (n = 2, 3) Complexes for M = Copper(I), Silver(I), and Gold(I)

2012 ◽  
Vol 65 (7) ◽  
pp. 811 ◽  
Author(s):  
Peter C. Healy ◽  
Bradley T. Loughrey ◽  
Michael L. Williams
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Structural Analysis ◽  
Single Crystal ◽  
Copper Complex ◽  
Electrospray Mass Spectrometry ◽  
Structural Studies ◽  
Space Group ◽  
X Ray ◽  
Bond Lengths

Tetraphenylborate salts of the 1 : 2 tetrahedral bis(bidentate) complexes of copper(i), silver(i), and gold(i) with cis-bis(diphenylphosphino)ethene (dppey), [M(Ph2PCH=CHPPh2)2]BPh4, cis-bis(diphenylphosphino)ethane (dppe), and cis-bis(diphenylphosphino)propane (dppp), [M(Ph2P–R–PPh2)2]BPh4 (R = (CH2)2, (CH2)3), have been prepared and characterized by NMR spectroscopy, electrospray mass spectrometry, and single crystal X-ray structural analysis at 200 K. Structures of the dppey complexes as acetone solvates show the Cu and Ag complexes to be isostructural with the previously reported Au complex, crystallizing in space group P 21/n with a ~ 25.5, b ~ 15.6, and c ~ 34.2 Å, and β ~ 103°. Structures of the dppe complexes show the copper complex to crystallize in the chiral space group P21 with a 11.8954(5), b 20.1904(5), and c 14.8999(5) Å, and β 111.366(5)°. The Ag and Au complexes are isostructural, crystallizing in space group P21/c with a ~ 17.8, b ~ 17.6, and c ~ 20.9 Å, and β ~ 107°. Structures of the dppp complexes show the copper complex to crystallize in space group P21/c with a 17.8399(4), b 19.8803(4), and c 18.7165(3) Å, and β 102.197(2)°. The Ag and Au complexes are isostructural, crystallizing in space group P21/n with a ~ 17.7, b ~ 18.6, and c ~ 19.6 Å, and β ~ 100°. Across the three series of complexes, the M–P bond lengths increase in the order Cu < Au < Ag with Cu–P = 2.281(3)–2.314(1) Å, average 2.30(1) Å; Au–P = 2.363(1)–2.4322(8) Å, average 2.40(2) Å, and Ag–P = 2.445(1)–2.5303(5) Å average 2.49(2) Å.

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.

Crystal structure of β-Cu2P2O7

1968 ◽  
Vol 46 (4) ◽  
pp. 605-612 ◽  
Author(s):  
B. E. Robertson ◽  
C. Calvo
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Low Temperature ◽  
Thermal Parameters ◽  
X Ray ◽  
Bond Lengths ◽  
Disordered Structure ◽  
Anisotropic Motion ◽  
Axial Bond ◽  
Ray Methods

The crystal structure of β-CU2P2O7 has been determined by X-ray methods. The crystals are monoclinic with a = 6.827(8) Å, b = 8.118(10) Å, c = 4.576(6) Å, β = 108.85(10)°, Z = 2, and space group C2/m. This structure is analogous to that of the mineral thortveitite and the high temperature forms of the pyrophosphates of Zn, Mg, and Mn. The cations are octahedrally coordinated to oxygen atoms with equatorial Cu—O bonds of 2.00 Å and 1.94 Å while the axial bond lengths are 2.58 Å. The anion has inner P—O bonds of 1.542 Å and average terminal bonds of 1.509 Å. In addition to the usual refinement with anisotropic thermal parameters, the structure has been refined in terms of a disordered structure generated from the low temperature α form of CU2P2O7. This disordered model agrees as well with the data (R = 0.12) as the structure based on the thortveitite structure with large anisotropic motion assigned to the atoms.

Structural parameters for the chair or twist-boat conformations of 1,3-dioxa-5,6-benzocycloheptene and its 2-methyl and 2,2-dimethyl derivatives

1986 ◽  
Vol 64 (3) ◽  
pp. 500-506 ◽  
Author(s):  
Robert St-Amour ◽  
Marc J. Olivier ◽  
Maurice St-Jacques ◽  
François Brisse
Keyword(s):  
Low Temperature ◽  
Oxygen Atom ◽  
Structural Parameters ◽  
Lone Pair ◽  
Molecular Conformations ◽  
X Ray ◽  
Bond Lengths ◽  
Structural Differences ◽  
Back Donation ◽  
Twist Boat

Low temperature X-ray studies of 1,3-dioxa-5,6-benzocycloheptene (1) and its 2-methyl (2) and 2,2-dimethyl derivatives (3) show that 1 and 2 exist in the crystal state exclusively in the chair (C) form while 3 exists exclusively in the twist-boat (TB) form. The final values of the agreement index, Rw, are 0.048, 0.059, and 0.046 for 1, 2, and 3, respectively. Significant structural differences between the g+g+ arrangement of the acetal moiety with the TB form and the g+g− disposition in the C form are revealed. These differences can be interpreted as arising from a less efficient back-donation of an antiperiplanar lone pair on the oxygen atom in the g+g+ relative to the g+g− arrangement. Furthermore, the C—O bond lengths shed some light on the hybridization state of the lone pairs of electrons on oxygen. Finally the results are used to rationalize nmr observations in terms of molecular conformations in solution.

scholarly journals The Crystal and Molecular Structure of Diazido-2,2′-bipyridinecopper(II)

1974 ◽  
Vol 52 (17) ◽  
pp. 3125-3133 ◽  
Author(s):  
Gordon W. Bushnell ◽  
Masood A. Khan
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Lengths ◽  
Square Planar ◽  
Copper Coordination ◽  
Cell Dimensions ◽  
Coordinate Bond

The crystal and molecular structure of diazido-2,2′-bipyridinecopper(II), C10H8N2(N3)2Cu, is determined by single crystal X-ray diffraction, and refined to an R value of 0.067. The cell dimensions are a = 664.9(2), b = 843.3(1), c = 1082.0(2) pm, α = 86.99(2)°, β = 87.77(3)°, γ = 78.59(2)°. The space group is [Formula: see text] (No. 2) with 2 molecules per unit cell and the measured density is 1.71(2) g cm−3. The copper coordination is square planar with two additional longer bonds. The coordinate bond lengths in pm to the bipyridine ligand are: Cu—N(1), 201.6(6); Cu—N(2), 201.9(6). The coordinate bonds to the azido ligands are: Cu—N(3), 194.9(6); Cu—N(6), 196.6(6). The longer bonds are: Cu—N(3)″, 268.0(8), Cu—N(6)′ 268.2(8). The N—N bond lengths within each azido ligand are unequal: N(3)—N(4), 118.2(10); N(4)—N(5), 115.4(11); N(6)—N(7), 119.2(9); N(7)—N(8), 114.8(9). The angles at N(3) and N(6) are both 130° and at N(4) and N(7) the angles are both 175(1)°. Each azide takes part in asymmetric bridging through a single nitrogen atom. The results are compared with other structural studies on azido complexes and to a nitrate complex of Ag(II) which is structurally similar.

Low‐Temperature X‐Ray Goniometer for Structural Studies of Crystal Transitions

1953 ◽  
Vol 24 (12) ◽  
pp. 1087-1095 ◽  
Author(s):  
R. Keeling ◽  
B. C. Frazer ◽  
R. Pepinsky
Keyword(s):  
Low Temperature ◽  
Structural Studies ◽  
X Ray
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