Chiral "basket handle" binaphthyl porphyrins: synthesis, catalytic epoxidation and NMR conformational studies

2010 ◽  
Vol 14 (07) ◽  
pp. 646-659 ◽  
Author(s):  
Eric Rose ◽  
Emma Gallo ◽  
Nicolas Raoul ◽  
Léa Bouché ◽  
Ariane Pille ◽  
...  
Keyword(s):  
Time Scale ◽  
Room Temperature ◽  
Conformational Equilibrium ◽  
Variable Temperature ◽  
Conformational Exchange ◽  
Iron Catalysts ◽  
Nmr Studies ◽  
Conformational Studies ◽  
H Nmr ◽  
Catalytic Epoxidation

Three "basket handle" porphyrins have been prepared by condensation of tetrakis-(α,β,α,β-2-aminophenyl)porphyrin atropoisomer with 1,1′-binaphthyl, 2,2′-dimethoxy, -3,3′-dicarbonylchloride, -3,3′-diacetylchloride and -3,3′-dipropanoylchloride. The epoxidation of styrene with the three iron catalysts, obtained after metalation of the free porphyrins, occurs with good yields and moderate ee up to 54%. These porphyrins showed unexpected conformational differences, as revealed by NMR spectroscopy. In particular, variable temperature NMR studies showed that the methoxy group in one of them undergoes intermediate conformational exchange on the 1H NMR time scale at room temperature. Lowering the temperature to -50 °C revealed the presence of four states in slow exchange on the NMR time scale. These results evidence a dynamic conformational equilibrium of the binaphthyl handles that adopt different, asymmetric positions with respect to the porphyrin plane.

Synthese und spektroskopische Charakterisierung neuer Bis(thiolato)- und Endithiolato-bis(η5-cyclopentadienyl)hafnium(IV)-Komplexe / Synthesis and Spectroscopic Characterisation of New Bis(thiolato)- and Endithiolato-bis(η5-cyclopentadienyl)hafnium(IV) Complexes

1985 ◽  
Vol 40 (10) ◽  
pp. 1338-1343 ◽  
Author(s):  
Hartmut Köpf ◽  
Thomas Klapötke
Keyword(s):  
Room Temperature ◽  
Variable Temperature ◽  
Nmr Studies ◽  
H Nmr ◽  
Envelope Conformation ◽  
Spectroscopic Characterisation ◽  
Chelate Rings

The hafnocene thiophenolates Cp2Hf(SC6H4R)2 (Cp = η5-C5Hs; R = H, o-Me,p-Me, p-NH2) and cis- 1.2-endithiolates Cp2Hf(S2C6H4), Cp2Hf(S2C6H3Me-4), and Cp2Hf{S2C2(CN)2} were prepared by reaction of Cp2HfCl2 with equivalent amounts of the appropriate lithium thiolates or endithiolates, or with Na2S2C2(CN)2. respectively. From variable temperature 1H NMR studies of the endithiolate complexes with aromatic ligands a folded (“envelope”) conformation of the five-membered chelate rings, undergoing rapid inversion at room temperature, can be derived.

Synthesis and conformational studies of 9-benzyloxy-18-substituted [3.3]metacyclophanes

2015 ◽  
Vol 93 (11) ◽  
pp. 1161-1168 ◽  
Author(s):  
M. Monarul Islam ◽  
Tomiyasu Hirotsugu ◽  
Taisuke Matsumoto ◽  
Junji Tanaka ◽  
Takehiko Yamato
Keyword(s):  
Solid State ◽  
Intramolecular Cyclization ◽  
Acid Treatment ◽  
Room Temperature ◽  
Coupling Reaction ◽  
Chair Conformation ◽  
Cyclization Reaction ◽  
Conformational Studies ◽  
X Ray ◽  
H Nmr

A series of syn-[3.3]metacyclophanes (MCPs) containing internal substituted benzyloxy group have been synthesized by the modified TosMIC coupling reaction followed by acid treatment and Wolff–Kishner reduction. anti-Mono- and di-benzyloxy[3.3]MCPs are synthesized by O-benzylation of the corresponding hydroxy[3.3]MCPs, which are obtained by demethylation of methoxy[3.3]MCPs with BBr3 at room temperature. An interesting and intriguing result was obtained when syn-6,15-di-tert-butyl-9-methoxy-18-methyl[3.3]MCP-2,11-dione was treated with TMSI to afford the formation of a dihydrobenzofuran ring by a nucleophilic intramolecular cyclization reaction. The 1H NMR and X-ray analysis of 6a confirms that it adopts a syn (chair–chair) conformation in both solution and solid state.

Nuclear magnetic resonance studies of the methylammonium hexahalotellurates

1992 ◽  
Vol 70 (3) ◽  
pp. 849-855 ◽  
Author(s):  
Mark R. MacIntosh ◽  
Marco L. H. Gruwel ◽  
Katherine N. Robertson ◽  
Roderick E. Wasylishen
Keyword(s):  
Line Shape ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Solid Phase ◽  
Variable Temperature ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
H Nmr ◽  
Nmr Study ◽  
Correlated Motion

A 2H and 14N NMR study of the solid methylammonium hexahalotellurates, (MA)2TeX6 (MA = CH3ND3+ or CD3NH3+, X = Cl, Br, and I), has been undertaken to characterize the dynamics of the methylammonium (MA) ion as a function of temperature. At room temperature, the MA ion in the hexachlorotellurate (solid II) is confined to C3 jumps about the C—N axis while a small angle libration of the C—N axis is occurring. In the room temperature phase, solid I, of (MA)2TeBr6 and (MA)2TeI6 the MA ions are performing overall reorientations on the ps time scale, averaging the 2H nuclear quadrupolar interactions to zero. Variable temperature 2H NMR spin-lattice relaxation times, T1, indicate an activation energy, EA, for "isotropic" reorientations of the CH3ND3+ ion of 5.2 ± 0.5 and 2.6 ± 0.3 kJ mol−1 for X = Br and I, respectively. Deuterium T1 values for C-deuterated MA ion in the hexaiodotellurate indicate an EA for whole-ion reorientation of 3.1 ± 0.3 kJ mol−1. At any given temperature, the correlation time, τc, derived from the T1 results was found to be the same for the two deuterium-labelled hexaiodotellurates. The similarity of both the EA and the τc values implies correlated motion of the methyl and ammonium groups. The 14N T1 results for solid I of (MA)2TeI6 indicate that C—N axis motions, with an EA = 5.6 ± 0.6 kJ mol−1, are more hindered than N—D or C—D bond dynamics. The 2H NMR spectra for (MA)2TeI6 (solid II) and (MA)2TeBr6 (solids II, III, and IV) are characterized by a Pake doublet line shape. The measured peak-to-peak splittings are less than what is predicted by C3 motion about the molecular symmetry axis. It is possible to model these line shapes by postulating that C3 rotations of the methyl and ammonium groups occur as the C—N axis librates in an effective cone about the position of the static molecular axis. For (CH3ND3)2TeBr6 and (CD3NH3)3TeBr6 the peak-to-peak splittings in the 2H NMR spectra were measured as a function of temperature in solid phases II, III, and IV and were found to be similar. Finally, the 2H NMR line shape relaxation for (MA)2TeBr6 (solid III) displays an orientation dependence indicating that rotations about the C—N axis are discrete rather than diffusive in nature. For solid phase II of (MA)2TeCl6, the line shape is observed to relax isotropically, implying that continuous C3 rotations are taking place. Keywords: 2H and 14N NMR, methylammonium hexahalotellurates, molecular motion.

1H nuclear magnetic resonance, differential scanning calorimetry, and electrical conductivity studies on the phase transitions of pentylammonium chloride and the cationic self-diffusion in its rotator phase

1988 ◽  
Vol 66 (8) ◽  
pp. 1961-1969 ◽  
Author(s):  
Shigehiko Iwai ◽  
Ryuichi Ikeda ◽  
Daiyu Nakamura
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
Differential Scanning Calorimetry ◽  
Room Temperature ◽  
Stable Phase ◽  
Scanning Calorimetry ◽  
Nmr Studies ◽  
Self Diffusion ◽  
H Nmr ◽  
Rotator Phase

Measurements of 1H nmr, differential thermal analysis, and differential scanning calorimetry have revealed that solid pentylammonium chloride, cooled rapidly from room temperature, forms a mixture of the stable and metastable low-temperature phases below the phase transition temperature, Ttr (238 K). The sample annealed just below Ttr for 3 h was shown to consist of a single stable phase down to about 100 K, indicating the existence of a time-consuming phase transition taking place successively just below the normal transition. In the rotator phase obtainable above Ttr (257 K), 1H nmr studies proved the presence of axial rotation of the whole cation about the long axis, similar to n-paraffins in their rotator phase. Above room temperature, the onset of the translational self-diffusion of the cations within 2D planes in the layer structure of the rotator phase was detected by measuring the temperature dependence of electrical conductivity as well as 1H T1 and T1p. 2D self-diffusion constants and diffusional correlation times evaluated from the electrical conductivity observed between room and the melting temperatures indicate that the 2D cationic diffusion near the melting point is as fast as 3D self-diffusion in usual plastic crystals. Cationic motions in the two different rotator phases α and α′ are compared.

Symmetry, disorder, and dynamics in solid crown ether complexes: 2H NMR studies of 15-crown-5·NaI, 15-crown-5·NaClO4, and 21-crown-7·KI

1999 ◽  
Vol 77 (11) ◽  
pp. 1911-1921 ◽  
Author(s):  
G W Buchanan ◽  
M Gerzain ◽  
C I Ratcliffe
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
Crown Ether ◽  
Detailed Analysis ◽  
Room Temperature ◽  
2H Nmr ◽  
Nmr Studies ◽  
H Nmr ◽  
Line Shapes ◽  
Crown Ether Complexes

2H NMR line shapes have been obtained as a function of temperature for partially deuteriated 15-crown-5·NaI, 15-crown-5·NaClO4 and 21-crown-7·KI. Sudden changes in the line shapes above 330 K correspond to phase transitions: DSC shows transitions at 338, 347 K for 15-crown-5·NaI, and 356, 374, 383 K for 15-crown-5·NaClO4. The 2H NMR line shapes for the room temperature (RT) phases show the onset of a motion of the macrocycles above 200K, which is rapid a little above room temperature. Through detailed analysis of the complicated line shapes it has been shown that the most consistent interpretation of the dynamics in these RT phases is a "merry-go-round" type of motion similar to that found for 18-crown-6 and 12-crown-4 complexes in which O-CH2-CH2 units exchange sites around the ring, simultaneously adjusting their conformation to fit the site. In the high-temperature phases of all three complexes all the ring atoms are dynamically equivalent. This can only happen through a combination of increased symmetry and disorder for which possible models have been devised.Key words: 2H NMR, crown ether complexes, dynamics, disorder.

Lewis acidic titanium species: the synthesis, structure, bonding and molecular modelling considerations of the complexes Ti(NR2)3Cl (R = Me, Et)

1991 ◽  
Vol 69 (2) ◽  
pp. 357-362 ◽  
Author(s):  
David G. Dick ◽  
Roger Rousseau ◽  
Douglas W. Stephan
Keyword(s):  
Molecular Modelling ◽  
Energy Minimization ◽  
Variable Temperature ◽  
Structural Data ◽  
Steric Effects ◽  
Monoclinic Space Group ◽  
Nmr Studies ◽  
Space Group ◽  
H Nmr ◽  
Multiple Bonding

Reaction of simple amides with TiCl4 affords mixed amido-chloride species Ti(NR2)4−nCln. The trisamide-chloride species Ti(NR2)3Cl can be prepared directly employing three equivalents of amide or by reaction Ti(NR2)4 with TiCl4. The compound Ti(NMe2)3Cl, 1, crystallizes in the trigonal space group [Formula: see text] with a = 11.525(5), c = 14.939(3) Å, Z = 6, and V = 1718(1) Å3. The compound Ti(NEt2)3Cl, 2, crystallizes in the monoclinic space group P21/c, with a = 8.385(2) Å, b = 15.958(2) Å, c = 14.230(4) Å, β = 107.79(1)°, Z = 4, and V = 1813(1) Å3. The geometry of the Ti coordination sphere in these complexes is best described as pseudo-tetrahedral. The structural data are consistent with Ti—N multiple bonding. Preliminary results of EHMO calculations are consistent with dπ—pπ Ti—N bonding. Attempts to replace the halides with phosphides (LiPR2, R = Me, Et, Ph) led not to the Ti(IV) phosphido species, but rather to redox chemistry yielding Ti(III) amides and P2R4. The barrier to rotation about the Ti—N bonds has been considered. Variable temperature 1H NMR studies reveal that the barrier is small. Extended Hückel total energy minimization calculations have been performed. In addition, MMX calculations of the barrier to Ti—N rotation are reported. The results of these calculations imply that the rotational barrier is dominated by steric effects. Key words: titanium amides, structures, Ti—N bonding

scholarly journals The syntheses and NMR studies of hexadeca- and octaneopentoxyphthalocyanines

2002 ◽  
Vol 80 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Namrta Bhardwaj ◽  
John Andraos ◽  
Clifford C Leznoff
Keyword(s):  
Nmr Spectra ◽  
Variable Temperature ◽  
Nickel Chloride ◽  
Nmr Studies ◽  
Restricted Rotation ◽  
H Nmr

The syntheses of 3,6-dineopentoxyphthalonitrile and 3,4,5,6-tetraneopentoxyphthalonitrile are described. Condensation of these phthalonitriles with nickel chloride in N,N-dimethylaminoethanol yielded 1,4,8,11,15,18,22,25-octaneopentoxyphthalocyaninato nickel(II) (3) and 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecaneopentoxyphthalocyaninato nickel(II) (7). The 1H NMR spectra of these phthalocyanines and the related 2,3,9,10,16,17,23,24-octaneopentoxyphthalocyaninato nickel(II) (8) at temperatures from 205 to 330 K in toluene-d8 exhibited various degrees of restriction of rotation of the neopentoxy groups. Compound 7 exhibited a single atropisomer at 235 K.Key words: neopentoxy substituted phthalocyanines, variable temperature NMR, restricted rotation.

Trihapto cycloheptatrienyl molybdenum and tungsten dicarbonyl compounds incorporating tridentate chelating dimethyl(1-pyrazolyl)(ethanolamine)gallate ligands

1980 ◽  
Vol 58 (21) ◽  
pp. 2278-2285 ◽  
Author(s):  
Kenneth S. Chong ◽  
Alan Storr
Keyword(s):  
Nitrogen Atom ◽  
Low Temperature ◽  
Physical Properties ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Amino Nitrogen ◽  
Nmr Studies ◽  
Dicarbonyl Compounds ◽  
H Nmr ◽  
And Tungsten

The synthesis and physical properties of a series of cycloheptatrienyl molybdenum and tungsten dicarbonyl compounds incorporating dimethyl(1-pyrazolyl)(ethanolamine)gallate ligands have been investigated. The monomeric, pseudo octahedral, complexes have the organogallate ligand occupying a set of facial positions with the cycloheptatrienyl ring situated opposite to the amino nitrogen atom. Proton nmr studies have shown the η3-C7H7 ligand of the complexes to be fluxional in solution at room temperature. In the low temperature limiting 1H nmr spectra of the complexes in solution, however, it is possible to distinguish ail seven protons of the static η3-C7H7 ring owing to the asymmetric nature of the octahedral molecules.

Iridium(I) complexes containing bidentate pyrazolylgallate ligands. X-ray crystal structures of [Me2Gapz2]Ir(COD), [Ir(μ-pz)(CO)2]2, and [Ir(μ-3,5-Me2pz)(CO)2]2

1985 ◽  
Vol 63 (3) ◽  
pp. 692-702 ◽  
Author(s):  
Sophia Nussbaum ◽  
Steven J. Rettig ◽  
Alan Storr ◽  
James Trotter
Keyword(s):  
Crystal Structures ◽  
Variable Temperature ◽  
Hydrogenation Reaction ◽  
Synthesis And Characterization ◽  
Nmr Studies ◽  
X Ray ◽  
H Nmr ◽  
Measurable Activity

The synthesis and characterization of a number of Ir(I) complexes incorporating bidentate, chelating, pyrazolylgallate ligands are described. Non-rigidity for some of the complexes in solution has been demonstrated by variable temperature 1H nmr studies. Crystal structures of three complexes, [Me2Gapz2]Ir(COD), [Ir(μ-pz)(CO)2]2, and [Ir(μ-3,5-Me2pz)(CO)2]2 are reported and confirm the expected boat conformations for the six-membered M—(N—N)2—Ir rings (where M = Ir or Ga) in the compounds. One of the complexes studied has exhibited measurable activity as a catalyst in the hydrogenation reaction of cyclohexene.

Sign in / Sign up

Export Citation Format

Share Document