共查询到20条相似文献,搜索用时 15 毫秒
1.
J.-P. Albrand A. Cogne D. Gagnaire J. Martin J.-B. Robert J. Verrier 《Magnetic resonance in chemistry : MRC》1971,3(1):75-82
The NMR spectra of the trivalent fluorophospholanes ( 1, 2, 3 ) have been analysed at length. The absolute signs of the 3J(P? H) and 4J(F? H) coupling constants have been referred to the known negative sign of the 1J(P? F) coupling constant from selective heteronuclear double resonance experiments. The 3J(P? O? C? H) and 3J(P? N? C? H) coupling are positive. The weak values observed for 3J(P? S? C? H) have opposite signs, the larger being positive. All the 4J(F? P? X? C? H) coupling constants are positive showing a lack of stereospecificity. 相似文献
2.
Jean-Pierre Albrand Didier Gagnaire Jean Martin Jean-Bernard Robert 《Magnetic resonance in chemistry : MRC》1973,5(1):33-41
The proton NMR spectral analysis of eight different 1,3,2-dithiaphospholanes with various groups attached to the phosphorus atom has been performed. The AA′BB′X (X phosphorus atom) system shows that the two 3J(P? S? C? H) coupling constants have a small magnitude and opposite signs. Using the 3J(HH) values, the torsion about the C4—C5 bond has been evaluated. The conformational requirements in the two isomers of the 2 phenyl-4-methyl-1,3,2-dithiaphospholane are also discussed. 相似文献
3.
Marie-Paule Simonnin Claude Charrier Marie-Jos Lecourt 《Magnetic resonance in chemistry : MRC》1969,1(1):27-49
The signs of the phosphorus-proton coupling constants in various allenic organophosphorus compounds have been determined by either analysis of the AB2X spectra or double resonance. Probable absolute signs have been obtained by taking 3J(P? H) as positive. In allenic phosphine oxides, the following signs are obtained: 2J(P? H) +ve, 3J(P? H) +ve, 4J(P? H) ?ve, 5J(P? H) +ve and the 4J(P? H) coupling constant varies mostly with the inductive effect of the substituents bound to the phosphorus atom. In allenic phosphines, these sings are: 2J(P? H) +ve, 3J(P? H) +ve, 4J(P? H) ?ve and +ve and the 4J(P? H) coupling constant varies with both the inductive and resonance effects to the substituents. This coupling constant is negative except when the phosphorus atom is bound to groups which are electron-donating by resonance effects. These results are discussed in relation to the pπ? dπ bonding in phosphine. 相似文献
4.
Marie-Paule Simonnin Minh Lequan Marie-Jos Lecourt 《Magnetic resonance in chemistry : MRC》1970,2(4):369-378
Satellites corresponding to metal-proton coupling constants through two and four bonds are observed in PMR spectra of Pb, Sn and Hg allenic derivatives. The relative signs of these coupling constants are deduced from analysis of the satellite spectra: 2J(X? H) and 4J(X? H) are of opposite signs for X = 207Pb, 119Sn, 117Sn and of same sign for X = 199Hg. Probable absolute signs of reduced coupling constants are discussed in relation to published data: 2K(X? C? H) is probably positive for X = 207Pb, 119Sn, 117Sn and 199Hg. 4K(X? C?C?C? H) is probably negative for X = 207Pb, 119Sn, 117Sn and positive for X = 199Hg. 相似文献
5.
All J(P? H) and J(P? C) values, including signs, have been obtained in acetylenic and propynylic phosphorus derivatives, R2P(X)? C?C? H and R2P(X)? C?C? CH3 (X ? oxygen, lone pair and R ? C6H5, N(CH3)2, OC2H5, N(C6H5)2, Cl) from 1H and 13C NMR spectra. In PIV derivatives the following signs are obtained: 1J(P? C)+, 2J(P? C)+, 3J(P? C)+, 3J(P? H)+, 4J(P? H)? . Linear relations are observed between 1J(P? C), 2J(P? C) and 3J(P? C) versus 3J(P? H), indicating that these coupling constants are mainly dependent on the Fermi contact term, though the other terms of the Ramsey theory do not seem to be negligible for 1J(P? C) and 2J(P? C). In PIII derivatives these signs are: 1J(P? C)- and +, 2J(P? C)+, 3J(P? C)-, 3J(P? H)-, 4J(P? H)+. Only 3J(P? C) and 3J(P? H) reflect a small contribution of the Fermi contact term while in 1J(P? C) and 2J(P? C) this contribution seems to be negligible relative to the orbital and/or spin dipolar coupling mechanisms. 相似文献
6.
Using (FH)2 and (FH)3 to Bridge the σ‐Hole and the Lone Pair at P in Complexes with H2XP,for X=CH3, OH,H, CCH,F, Cl,NC, and CN
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Ab initio MP2/aug′‐cc‐pVTZ calculations are used to investigate the binary complexes H2XP:HF, the ternary complexes H2XP:(FH)2, and the quaternary complexes H2XP:(FH)3, for X=CH3, OH, H, CCH, F, Cl, NC, and CN. Hydrogen‐bonded (HB) binary complexes are formed between all H2XP molecules and FH, but only H2FP, H2ClP, and H2(NC)P form pnicogen‐bonded (ZB) complexes with FH. Ternary complexes with (FH)2 are stabilized by F?H???P and F?H???F hydrogen bonds and F???P pnicogen bonds, except for H2(CH3)P:(FH)2 and H3P:(FH)2, which do not have pnicogen bonds. All quaternary complexes H2XP:(FH)3 are stabilized by both F?H???P and F?H???F hydrogen bonds and P???F pnicogen bonds. Thus, (FH)2 with two exceptions, and (FH)3 can bridge the σ‐hole and the lone pair at P in these complexes. The binding energies of H2XP:(FH)3 complexes are significantly greater than the binding energies of H2XP:(FH)2 complexes, and nonadditivities are synergistic in both series. Charge transfer occurs across all intermolecular bonds from the lone‐pair donor atom to an antibonding σ* orbital of the acceptor molecule, and stabilizes these complexes. Charge‐transfer energies across the pnicogen bond correlate with the intermolecular P?F distance, while charge‐transfer energies across F?H???P and F?H???F hydrogen bonds correlate with the distance between the lone‐pair donor atom and the hydrogen‐bonded H atom. In binary and quaternary complexes, charge transfer energies also correlate with the distance between the electron‐donor atom and the hydrogen‐bonded F atom. EOM‐CCSD spin‐spin coupling constants 2hJ(F–P) across F?H???P hydrogen bonds, and 1pJ(P–F) across pnicogen bonds in binary, ternary, and quaternary complexes exhibit strong correlations with the corresponding intermolecular distances. Hydrogen bonds are better transmitters of F–P coupling data than pnicogen bonds, despite the longer F???P distances in F?H???P hydrogen bonds compared to P???F pnicogen bonds. There is a correlation between the two bond coupling constants 2hJ(F–F) in the quaternary complexes and the corresponding intermolecular distances, but not in the ternary complexes, a reflection of the distorted geometries of the bridging dimers in ternary complexes. 相似文献
7.
Nana Kim Prof. Ross A. Widenhoefer 《Angewandte Chemie (International ed. in English)》2018,57(17):4722-4726
Methoxide abstraction from gold acetylide complexes of the form (L)Au[η1‐C≡CC(OMe)ArAr′] (L=IPr, P(tBu)2(ortho‐biphenyl); Ar/Ar′=C6H4X where X=H, Cl, Me, OMe) with trimethylsilyl trifluoromethanesulfonate (TMSOTf) at ?78 °C resulted in the formation of the corresponding cationic gold diarylallenylidene complexes [(L)Au=C=C=CArAr′]+ OTf? in ≥85±5 % yield according to 1H NMR analysis. 13C NMR and IR spectroscopic analysis of these complexes established the arene‐dependent delocalization of positive charge on both the C1 and C3 allenylidene carbon atoms. The diphenylallenylidene complex [(IPr)Au=C=C=CPh2]+ OTf? reacted with heteroatom nucleophiles at the allenylidene C1 and/or C3 carbon atom. 相似文献
8.
The NMR spectra of fifteen para-substituted acetanilides, XC6H4·NH·CO·CH3 (X = NH·CO·Me; NH2; CO·OEt; COOH; Cl; OEt; F; H; OMe; CH3; NO2; C6H5; ? N?N? C6H5; Me3Si), have been recorded. δ and δNH are linearly related to Hammett's σp constant. The coupling J (o-H? H) between aromatic protons is mainly dependent on σR0. J(13C? H), in methyl group is approximatively constant in the series. 相似文献
9.
The 1H and 19F spectra of a variety of mono- and di- fluorinated pyridines are examined, and compared with the corresponding spectra of the pyridinium ions. The magnitudes and signs of the 1H? 19F coupling constants are in general in accord with those observed for the corresponding 1H? 1H couplings, with an exaggerated range. Large changes in the NMR parameters are observed on protonation of the nitrogen, 3J(H? F) changing sign in some of the α-fluoropyridine derivatives. 相似文献
10.
Rituparna Biswas Yumi Ida Dr. Michael L. Baker Saptarshi Biswas Paramita Kar Prof. Dr. Hiroyuki Nojiri Prof. Dr. Takayuki Ishida Prof. Dr. Ashutosh Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):3943-3953
Three new trinuclear nickel (II) complexes with the general composition [Ni3L3(OH)(X)](ClO4) have been prepared in which X=Cl? ( 1 ), OCN? ( 2 ), or N3? ( 3 ) and HL is the tridentate N,N,O donor Schiff base ligand 2‐[(3‐dimethylaminopropylimino)methyl]phenol. Single‐crystal structural analyses revealed that all three complexes have a similar Ni3 core motif with three different types of bridging, namely phenoxido (μ2 and μ3), hydroxido (μ3), and μ2‐Cl ( 1 ), μ1,1‐NCO ( 2 ), or μ1,1‐N3 ( 3 ). The nickel(II) ions adopt a compressed octahedron geometry. Single‐crystal magnetization measurements on complex 1 revealed that the pseudo‐three‐fold axis of Ni3 corresponds to a magnetic easy axis, being consistent with the magnetic anisotropy expected from the coordination structure of each nickel ion. Temperature‐dependent magnetic measurements indicated ferromagnetic coupling leading to an S=3 ground state with 2J/k=17, 17, and 28 K for 1 , 2 , and 3 , respectively, with the nickel atoms in an approximate equilateral triangle. The high‐frequency EPR spectra in combination with spin Hamiltonian simulations that include zero‐field splitting parameters DNi/k=?5, ?4, and ?4 K for 1 , 2 , and 3 , respectively, reproduced the EPR spectra well after a anisotropic exchange term was introduced. Anisotropic exchange was identified as Di,j/k=?0.9, ?0.8, and ?0.8 K for 1 , 2 , and 3 , respectively, whereas no evidence of single‐ion rhombic anisotropy was observed spectroscopically. Slow relaxation of the magnetization at low temperatures is evident from the frequency‐dependence of the out‐of‐phase ac susceptibilities. Pulsed‐field magnetization recorded at 0.5 K shows clear steps in the hysteresis loop at 0.5–1 T, which has been assigned to quantum tunneling, and is characteristic of single‐molecule magnets. 相似文献
11.
Martin Kaller Dipl.‐Chem. Stefan Tussetschläger Dr. Peter Fischer Priv.‐Doz. Dr. Christopher Deck Dipl.‐Chem. Angelika Baro Dr. Frank Giesselmann Prof. Dr. Sabine Laschat Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(37):9530-9542
Dibenzo[18]crown‐6 derivatives 1 with two lateral tetraalkyloxy o‐terphenyl units were prepared and converted to the corresponding complexes KX ?1 (X=halide, BF4, PF6, SCN) and NH4PF6 ?1 . Complexation was probed by MALDI‐TOF spectrometry and NMR spectroscopy. Downfield shifts of 1H NMR signals for complexes with soft anions Br, I, SCN, and PF6 indicated the presence of tight ion pairs, whereas complexes with hard anions F, Cl, or BF4 showed no or little shifts. In 13C NMR spectra, upfield shifts were detected for soft anions. The character of the anion also influenced the mesomorphic properties of complexes MX ?1 (M=K, NH4), which were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and XRD in comparison to neat 1 . Hard anions slightly stabilize or even destabilize the mesophase. Soft anions, however, improve the mesomorphic properties yielding mesophases with up to 70 °C phase widths in the case of KI ?1 , KPF6 ?1 , and NH4PF6 ?1 . For complexes KSCN ?1 with a soft and bridging anion, the balance between mesophase stabilization and high order is shifted in favor of the plastic crystal phase. 相似文献
12.
Addison N. Desnoyer Weiying He Shirin Behyan Weiling Chiu Jennifer A. Love Pierre Kennepohl 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(20):5259-5268
The electronic nature of Ni π-complexes is underexplored even though these complexes have been widely postulated as intermediates in organometallic chemistry. Herein, the geometric and electronic structure of a series of nickel π-complexes, Ni(dtbpe)(X) (dtbpe=1,2-bis(di-tert-butyl)phosphinoethane; X=alkene or carbonyl containing π-ligands), is probed using a combination of 31P NMR, Ni K-edge XAS, Ni Kβ XES, and DFT calculations. These complexes are best described as square planar d10 complexes with π-backbonding acting as the dominant contributor to M−L bonding to the π-ligand. The degree of backbonding correlates with 2JPP from NMR and the energy of the Ni 1s→4pz pre-edge in the Ni K-edge XAS data, and is determined by the energy of the π*ip ligand acceptor orbital. Thus, unactivated olefinic ligands tend to be poor π-acids whereas ketones, aldehydes, and esters allow for greater backbonding. However, backbonding is still significant even in cases in which metal contributions are minor. In such cases, backbonding is dominated by charge donation from the diphosphine, which allows for strong backdonation, although the metal centre retains a formal d10 electronic configuration. This ligand-induced backbonding can be formally described as a 3-centre-4-electron (3c-4e) interaction, in which the nickel centre mediates charge transfer from the phosphine σ-donors to the π*ip ligand acceptor orbital. The implications of this bonding motif are described with respect to both structure and reactivity. 相似文献
13.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(17):4812-4816
Methoxide abstraction from gold acetylide complexes of the form (L)Au[η1‐C≡CC(OMe)ArAr′] (L=IPr, P(tBu)2(ortho‐biphenyl); Ar/Ar′=C6H4X where X=H, Cl, Me, OMe) with trimethylsilyl trifluoromethanesulfonate (TMSOTf) at −78 °C resulted in the formation of the corresponding cationic gold diarylallenylidene complexes [(L)Au=C=C=CArAr′]+ OTf− in ≥85±5 % yield according to 1H NMR analysis. 13C NMR and IR spectroscopic analysis of these complexes established the arene‐dependent delocalization of positive charge on both the C1 and C3 allenylidene carbon atoms. The diphenylallenylidene complex [(IPr)Au=C=C=CPh2]+ OTf− reacted with heteroatom nucleophiles at the allenylidene C1 and/or C3 carbon atom. 相似文献
14.
Guy Pouzard Michel Rajzmann Hubert Bodot Louis Pujol 《Magnetic resonance in chemistry : MRC》1973,5(5):209-214
Proton–proton 3J, 4J and 5J NMR coupling constants have been calculated for cyclohexane and monosubstituted cyclohexane conformers (substitiuents: Li, CH3, OH, F) by the two methods mentioned. Comparing the two methods on the basis of group theory, we show the necessity to use the second. The results from this method are compared with those of the literature. 相似文献
15.
Roland W. Kunz Paul S. Pregosin Mercedes Camalli Francesco Caruso Luigi Zambonelli 《Helvetica chimica acta》1983,66(6):1661-1671
The 31P{1H}-NMR characteristics of the complexes [HgX2( 1 )] and [HgX2-(PPh2Bz)2] (X = NO3, Cl, Br, I, SCN, CN) and the solid state structures of the complexes [HgCl2( 1 )] and [HgI2( 1 )] ( 1 = 2,11-bis (diphenylphosphinomethyl)benzo-[c]phenanthrene) have been determined. The 1J(199Hg, 31P) values increase in the order CN < I < SCN < Br < Cl < NO3. The two molecular structures show a distorted tetrahedral geometry about mercury. Pertinent bond lengths and bond angles from the X-ray analysis are as follows: Hg? P = 2.485(7) Å and 2.509 (8) Å, Hg? Cl = 2.525 (8) Å and 2.505 (10) Å, P? Hg? P = 125.6(3)°, Cl? Hg? Cl = 97.0(3)° for [HgCl2( 1 )] and Hg? P = 2.491 (10) Å and 2.500(11) Å, Hg? I = 2.858(5) Å and 2.832(3) Å, P? Hg? P = 146.0(4)°, I? Hg? I = 116.9(1)° for [HgI2( 1 )]. The equation, derived previously, relating 1J(199Hg, 31P) and the angles P? Hg? P and X? Hg? X is shown to be valid for 1 . 相似文献
16.
Reactions of SnCl2 with the complexes cis‐[PtCl2(P2)] (P2=dppf (1,1′‐bis(diphenylphosphino)ferrocene), dppp (1,3‐bis(diphenylphosphino)propane=1,1′‐(propane‐1,3‐diyl)bis[1,1‐diphenylphosphine]), dppb (1,4‐bis(diphenylphosphino)butane=1,1′‐(butane‐1,4‐diyl)bis[1,1‐diphenylphosphine]), and dpppe (1,5‐bis(diphenylphosphino)pentane=1,1′‐(pentane‐1,5‐diyl)bis[1,1‐diphenylphosphine])) resulted in the insertion of SnCl2 into the Pt? Cl bond to afford the cis‐[PtCl(SnCl3)(P2)] complexes. However, the reaction of the complexes cis‐[PtCl2(P2)] (P2=dppf, dppm (bis(diphenylphosphino)methane=1,1′‐methylenebis[1,1‐diphenylphosphine]), dppe (1,2‐bis(diphenylphosphino)ethane=1,1′‐(ethane‐1,2‐diyl)bis[1,1‐diphenylphosphine]), dppp, dppb, and dpppe; P=Ph3P and (MeO)3P) with SnX2 (X=Br or I) resulted in the halogen exchange to yield the complexes [PtX2(P2)]. In contrast, treatment of cis‐[PtBr2(dppm)] with SnBr2 resulted in the insertion of SnBr2 into the Pt? Br bond to form cis‐[Pt(SnBr3)2(dppm)], and this product was in equilibrium with the starting complex cis‐[PtBr2(dppm)]. Moreover, the reaction of cis‐[PtCl2(dppb)] with a mixture SnCl2/SnI2 in a 2 : 1 mol ratio resulted in the formation of cis‐[PtI2(dppb)] as a consequence of the selective halogen‐exchange reaction. 31P‐NMR Data for all complexes are reported, and a correlation between the chemical shifts and the coupling constants was established for mono‐ and bis(trichlorostannyl)platinum complexes. The effect of the alkane chain length of the ligand and SnII halide is described. 相似文献
17.
Fátima Gómez-Alcocer Abril C. Castro J. Oscar C. Jimenez-Halla Noe Saldaña-Piña Murali V. Basavanag J. Eduardo Báez-García José Bonilla-Cruz Jorge A. López Gerardo González-García 《无机化学与普通化学杂志》2020,646(15):1274-1280
A series of three neutral, hexacoordinate tin(IV) complexes were synthesized by the reaction of 4,4'-dimethyl-2,2'-bipyridine (DMB) with SnX4, X = Cl, Br, and I, as starting materials. The complexes (DMB)SnX4 were characterized in solution by 1H, 13C, and 119Sn NMR spectroscopy, and in the solid-state by 119Sn MAS NMR spectroscopy. In addition, single-crystal X-ray diffraction and elemental analysis were used to confirm the molecular structures. In these complexes, the tin atom adopts a distorted octahedral arrangement and the DMB acts as a bidentate N,N'-chelate ligand. Computational DFT methods were also employed to gain more insight into the nature of the bonding in these complexes, including the hypothetical complexes (DMB)SnX4 (X = F, At). Additionally, the validity and reliability of the 119Sn NMR chemical shifts were examined. The calculated values were compared with the experimental signals and the effects of structure and solvent are discussed. Finally, all of the complexes (DMB)SnX4 were successfully tested for the ring-opening polymerization (ROP) of bulk ε-caprolactone under non-dried and aerobic conditions as precatalyst. 相似文献
18.
Christian A. Sandoval Dr. Fusheng Bie Aki Matsuoka Yoshiki Yamaguchi Dr. Hiroshi Naka Prof. Dr. Yuehui Li Koichi Kato Prof. Dr. Noriyuki Utsumi Kunihiko Tsutsumi Takeshi Ohkuma Prof. Dr. Kunihiko Murata Dr. Ryoji Noyori Prof. Dr. 《化学:亚洲杂志》2010,5(4):806-816
Aromatic ketones are enantioseletively hydrogenated in alcohols containing [RuX{(S,S)‐Tsdpen}(η6‐p‐cymene)] (Tsdpen=TsNCH(C6H5)CH(C6H5)NH2; X=TfO, Cl) as precatalysts. The corresponding Ru hydride (X=H) acts as a reducing species. The solution structures and complete spectral assignment of these complexes have been determined using 2D NMR (1H‐1H DQF‐COSY, 1H‐13C HMQC, 1H‐15N HSQC, and 1H‐19F HOESY). Depending on the nature of the solvents and conditions, the precatalysts exist as a covalently bound complex, tight ion pair of [Ru+(Tsdpen)(cymene)] and X?, solvent‐separated ion pair, or discrete free ions. Solvent effects on the NH2 chemical shifts of the Ru complexes and the hydrodynamic radius and volume of the Ru+ and TfO? ions elucidate the process of precatalyst activation for hydrogenation. Most notably, the Ru triflate possessing a high ionizability, substantiated by cyclic voltammetry, exists in alcoholic solvents largely as a solvent‐separated ion pair and/or free ions. Accordingly, its diffusion‐derived data in CD3OD reflect the independent motion of [Ru+(Tsdpen)(cymene)] and TfO?. In CDCl3, the complex largely retains the covalent structure showing similar diffusion data for the cation and anion. The Ru triflate and chloride show similar but distinct solution behavior in various solvents. Conductivity measurements and catalytic behavior demonstrate that both complexes ionize in CH3OH to generate a common [Ru+(Tsdpen)(cymene)] and X?, although the extent is significantly greater for X=TfO?. The activation of [RuX(Tsdpen)(cymene)] during catalytic hydrogenation in alcoholic solvent occurs by simple ionization to generate [Ru+(Tsdpen)(cymene)]. The catalytic activity is thus significantly influenced by the reaction conditions. 相似文献
19.
The NMR-spectrum of 7·7-difluoro-benzo-cyclopropene ( 2 ) has been analysed to obtain chemical shifts and spin, spin-coupling constants: δAA′ = 7·6026, δBB′ = 7·4834 ppm; JAB = 6·86, JAA′ = 7·45, JAB′ = 0·34 and JBB′ = 1·89 Hz. Heteronuclear double resonance experiments have been used to establish a positive sign for 4J(H? F) (3.64 Hz) and a negative sign for 5J(H? F) (?0·33 Hz) in this molecule. The results are discussed with reference to the structure of 2 and the NMR data found for benzo-cyclopropene. 相似文献
20.
Three new complexes, [Co(hfac)2(NIToPy)] (1), [CoCl2(NIToPy)2] (2), and [Co(NIToPy)3](ClO4)2 (3), with NIToPy = 2-(2-Pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-oxy-3-oxide, and hfac = hexafluoroacetylacetonate, have been synthesized. The compound 3 crystallized in the monoclinic space group P21, with two molecules in a unit cell of dimensions a = 10.565(4) Å, b = 14.714(9) Å, c = 14.596(7) Å, and β = 107.10(4)°. The temperature-dependent magnetic susceptibility measurements (4.2 K-300 K) for the complexes demonstrated strong antiferromagnetic exchange interaction between cobalt(II) ion and NIToPy radical spins with J = ?140.1 cm?1 for 1, J = ?94.2 cm?1 for 2, and J = ?161.8 cm?1 for 3, respectively. The magneto-structural correlation in these complexes has been discussed. 相似文献