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1.
Rachel E. M. Brooner Prof. Ross A. Widenhoefer 《Angewandte Chemie (International ed. in English)》2013,52(45):11714-11724
Cationic, two‐coordinate gold π complexes that contain a phosphine or N‐heterocyclic supporting ligand have attracted considerable attention recently owing to the potential relevance of these species as intermediates in the gold‐catalyzed functionalization of C? C multiple bonds. Although neutral two‐coordinate gold π complexes have been known for over 40 years, examples of the cationic two‐coordinate gold(I) π complexes germane to catalysis remained undocumented prior to 2006. This situation has changed dramatically in recent years and well‐defined examples of two‐coordinate, cationic gold π complexes containing alkene, alkyne, diene, allene, and enol ether ligands have been documented. This Minireview highlights this recent work with a focus on the structure, bonding, and ligand exchange behavior of these complexes. 相似文献
2.
C. David Sherrill Bobby G. Sumpter Mutasem O. Sinnokrot Michael S. Marshall Edward G. Hohenstein Ross C. Walker Ian R. Gould 《Journal of computational chemistry》2009,30(14):2187-2193
Several popular force fields, namely, CHARMM, AMBER, OPLS‐AA, and MM3, have been tested for their ability to reproduce highly accurate quantum mechanical potential energy curves for noncovalent interactions in the benzene dimer, the benzene‐CH4 complex, and the benzene‐H2S complex. All of the force fields are semi‐quantitatively correct, but none of them is consistently reliable quantitatively. Re‐optimization of Lennard‐Jones parameters and symmetry‐adapted perturbation theory analysis for the benzene dimer suggests that better agreement cannot be expected unless more flexible functional forms (particularly for the electrostatic contributions) are employed for the empirical force fields. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009 相似文献
3.
Yaeun Kang Hui Chen Dr. Yu Jin Jeong Wenzhen Lai Dr. Eun Hae Bae Sason Shaik Prof. Dr. Wonwoo Nam Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(39):10039-10046
The proximal axial ligand in heme iron enzymes plays an important role in tuning the reactivities of iron(IV)‐oxo porphyrin π‐cation radicals in oxidation reactions. The present study reports the effects of axial ligands in olefin epoxidation, aromatic hydroxylation, alcohol oxidation, and alkane hydroxylation, by [(tmp)+. FeIV(O)(p‐Y‐PyO)]+ ( 1 ‐Y) (tmp=meso‐tetramesitylporphyrin, p‐Y‐PyO=para‐substituted pyridine N‐oxides, and Y=OCH3, CH3, H, Cl). In all of the oxidation reactions, the reactivities of 1 ‐Y are found to follow the order 1 ‐OCH3 > 1 ‐CH3 > 1 ‐H > 1 ‐Cl; negative Hammett ρ values of ?1.4 to ?2.7 were obtained by plotting the reaction rates against the σp values of the substituents of p‐Y‐PyO. These results, as well as previous ones on the effect of anionic nucleophiles, show that iron(IV)‐oxo porphyrin π‐cation radicals bearing electron‐donating axial ligands are more reactive in oxo‐transfer and hydrogen‐atom abstraction reactions. These results are counterintuitive since iron(IV)‐oxo porphyrin π‐cation radicals are electrophilic species. Theoretical calculations of anionic and neutral ligands reproduced the counterintuitive experimental findings and elucidated the root cause of the axial ligand effects. Thus, in the case of anionic ligands, as the ligand becomes a better electron donor, it strengthens the FeO? H bond and thereby enhances its H‐abstraction activity. In addition, it weakens the Fe?O bond and encourages oxo‐transfer reactivity. Both are Bell–Evans–Polanyi effects, however, in a series of neutral ligands like p‐Y‐PyO, there is a relatively weak trend that appears to originate in two‐state reactivity (TSR). This combination of experiment and theory enabled us to elucidate the factors that control the reactivity patterns of iron(IV)‐oxo porphyrin π‐cation radicals in oxidation reactions and to resolve an enigmatic and fundamental problem. 相似文献
4.
Ion Pairing,H‐bonding,and π‐π Interactions in Cobalt(II) Compound Containing Guanidinium Counter Ion
Shabnam Sheshmani Hossein Aghabozorg Fahimeh Mohammad Panah Robabeh Alizadeh Guido Kickelbick Bahar Nakhjavan Abolghasem Moghimi Farshid Ramezanipour Hamid Reza Aghabozorg 《无机化学与普通化学杂志》2006,632(3):469-474
A novel proton transfer compound, (GH)2(phendc), ( 1 ), was synthesized from the reaction of 1,10‐phenanthroline‐2,9‐dicarboxylic acid, phendcH2, and guanidine hydrochloride, (GH)(Cl), (G: guanidine). The characterization was performed using IR, 1H and 13C NMR spectroscopy. The cobalt(II) compounds were synthesized using proton transfer compounds containing guanidinium counter ion. These proton transfer compounds are (GH)2(phendc), and (GH)2(pydc) (pydcH2: 2,6‐pyridinedicarboxylic acid). The chemical formulae and space groups are (GH)2[Co(phendc)2]·4H2O, (2) , and (GH)2[Co(H2O)6][Co(pydc)2]2, P21/n (3) . Non‐covalent interactions such as ionpairing, hydrogen bonding and π‐π stacking are discussed. 相似文献
5.
Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Prof. Dr. J. Oscar C. Jiménez‐Halla Dr. Eduard Matito Jonas H. Muessig 《Angewandte Chemie (International ed. in English)》2018,57(2):412-416
The reaction of tetraiododiborane (B2I4) with trans‐[Pt(BI2)I(PCy3)2] gives rise to the diplatinum(II) complex [{(Cy3P)(I2B)Pt}2(μ2:η3:η3‐B2I4)], which is supported by a bridging diboranyl dianion ligand [B2I4]2?. This complex is the first transition‐metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B2X4 (X=halide) unit of any type to a metal center. 相似文献
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Both tetrakis(trimethylphosphine)cobalt(0) and methyltetrakis(trimethylphosphine)cobalt(I) react with 2‐(benzylideneamino)pyridine ( 1 ) exclusively giving a complex of composition (η2(N,C)‐2‐Py‐N=CH‐C6H5)Co(PMe3)3 ( 2 ), which is shown by single‐crystal X‐ray diffraction to constitute the first π‐coordinate imine cobalt(0) complex. The route of formation is proposed and discussed. 相似文献
7.
Bi‐Yun Su Jia‐Xiang Wang Xiang Liu Qian‐Ding Li 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(8):851-854
In the title compound, [Ni(C12H11N2)2], the NiII cation lies on an inversion centre and has a square‐planar coordination geometry. This transition metal complex is composed of two deprotonated N,N′‐bidentate 2‐[(phenylimino)ethyl]‐1H‐pyrrol‐1‐ide ligands around a central NiII cation, with the pyrrolide rings and imine groups lying trans to each other. The Ni—N bond lengths range from 1.894 (3) to 1.939 (2) Å and the bite angle is 83.13 (11)°. The Ni—N(pyrrolide) bond is substantially shorter than the Ni—N(imino) bond. The planes of the phenyl rings make a dihedral angle of 78.79 (9)° with respect to the central NiN4 plane. The molecules are linked into simple chains by an intermolecular C—H...π interaction involving a phenyl β‐C atom as donor. Intramolecular C—H...π interactions are also present. 相似文献
8.
Santhosh Kumar K. S. Dr. Yugang Li Dr. Yves Gnanou Dr. Ulrich Baisch Dr. Yohan Champouret Dr. Rinaldo Poli Prof. Kiyoshi C. D. Robson W. Stephen McNeil Prof. 《化学:亚洲杂志》2009,4(8):1257-1265
Complexes Co[OC(Ph)CHC(Me)NAr]2 [Ar=Ph, 1 ; o,o′‐C6H3Me2 (Xyl), 2 ; p‐C6H4CF3, 3 ] are tested in the polymerization of vinyl acetate (VAc) initiated by V‐70 (0.8 equiv) at 30 °C. Polymerization occurs without any notable induction time yielding PVAc with relatively low polydispersity, but with higher than expected Mn values, which indicates inefficient trapping processes. The apparent polymerization rate constant varies in the order 2 > 1 > 3 . Controlled polymer growth is also observed when the polymerization is conducted in the presence of a much higher V‐70/ 1 ratio, demonstrating that this system can also function as a transfer agent in a degenerative transfer process. Competition between chain growth and catalyzed chain transfer (CCT) is also observed, the latter prevailing at higher temperatures. Comparison of these results with previous reports on bis(β‐diketonato) complexes allows a separate assessment of ligand electronic and steric effects in the ability to control polymerization. 相似文献
9.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(2):68-71
The features of porphyrins defining their functionality are related to their conformational flexibility. The degree of nonplanarity of metalloporphyrins depends directly on the number of substituents, their size and their location. The introduction of substituents in the meso positions of β‐substituted porphyrins increases the steric interaction and leads to distortions of the porphyrin core. Increasing the distortion of the porphyrin core would augment the bathochromic (red) shift of the electronic absorption spectra. A new nonsymmetrical 2,3,7,8,12,13,17,18‐octaethyl‐5‐[(methylimino)methyl]porphyrin complex of palladium(II), [Pd(C38H47N5)], was synthesized and characterized by NMR, mass spectrometry and X‐ray analysis. The features of the electronic absorption spectrum of the synthesized complex are explained by the planarity of the porphyrin core and the π‐system of the imino group orthogonal to it. 相似文献
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Orientational Preference of Long,Multicenter Bonds in Radical Anion Dimers: A Case Study of π‐[TCNB]22− and π‐[TCNP]22−
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Dr. Marçal Capdevila‐Cortada Prof. Joel S. Miller Prof. Juan J. Novoa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6420-6432
The similar shape and electronic structure of the radical anions of 1,2,4,5‐tetracyanopyrazine (TCNP) and 1,2,4,5‐tetracyanobenzene (TCNB) suggest a similar relative orientation for their long, multicenter carbon?carbon bond in π‐[TCNP]22? and in π‐[TCNB]22?, in good accord with the Maximin Principle predictions. Instead, the two known structures of π‐[TCNP]22? have a D2h(θ=0°) and a C2(θ=30°) orientation (θ being the dihedral angle that determines the rotation of one radical anion relative to the other along the axis that passes through center of the two six‐membered rings). The only known π‐[TCNB]22? structure has a C2(θ=60°) orientation. The origin of these preferences was investigated for both dimers by computing (at the RASPT2/RASSCF(30,28) level) the variation with θ of the interaction energy (Eint) and the variation of the Eint components. It was found that: 1) a long, multicenter bond exists for all orientations; 2) the Eint(θ) angular dependence is similar in both dimers; 3) for all orientations the electrostatic component dominates the value of Eint(θ), although the dispersion and bonding components also play a relevant role; and 4) the Maximin Principle curve reproduces well the shape of the Eint(θ) curve for isolated dimers, although none of them reproduce the experimental preferences. Only after the (radical anion).? ??? cation+ interactions are also included in the model aggregate are the experimental data reproduced computationally. 相似文献
12.
Peng Cheng Lei Z. Zhang Wei‐Ming Bu Jiu‐He Peng Shi‐Ping Yan Dai‐Zheng Liao Zong‐Hui Jiang 《无机化学与普通化学杂志》2003,629(11):1996-1999
Three novel copper(II) complex [Cu2(bpa)(μ‐PhCO2)](ClO4)2 ( 1 ), [Cu2(bpa) (μ‐pyz)](ClO4)2 ( 2 ), and [Cu(Hbpa)](ClO4)2·2CH3CN ( 3 ) have been synthesized by the reaction of Hbpa with Cu(ClO4)2·6H2O in the presence and absence of exogenous ligands (where Hbpa = N, N'‐bis(picolinidene‐N‐oxide)‐2‐hydroxy‐1, 3‐diamino‐propane). Molecular structures of these compounds have been elucidated by single crystal X‐ray diffraction. 1 and 2 are both binuclear complexes in which two copper atoms are linked by the endogenous alkoxide oxygen and the exogenous benzoate and pyrazolate ligands, respectively. 3 consists of a one‐dimensional polymeric structure, in which Hbpa functions as a bridging mode. 相似文献
13.
Theoretical investigation on local electronic structure and stability of the π–π stacking interaction of pyrazinamide (PZA) with armchair (5,5) and zigzag (9,0) single‐walled carbon nanotubes (SWCNTs) is performed using density functional theory (DFT). PZA is physisorbed onto nanotube sidewall through interaction of π orbitals of PZA and SWCNT and the enhanced structural stability of PZA/SWCNT systems is due to weak side‐on rather than the head‐on π‐interactions. The physisorption of PZA onto SWCNT sidewall is thermodynamically favored; as a consequence, it modulates the electronic properties of pristine nanotube in the vicinity of Fermi region and π–π stacked interactions is stronger in (9,0) SWCNT compared to (5,5) SWCNT. The density of states (DOS) analysis show that PZA contributes toward the enhancement of electronic states. Projected DOS and frontier orbital analysis in the vicinity of Fermi level region suggest the electronic states to be contributed from SWCNT rather than PZA. In addition, hybrid DFT calculation which includes the dispersion correction is employed to explain the non‐covalent π–π stacking interaction between PZA and SWCNT. The local density approximation and GGA results are compared with DFT‐D to explain near about accurately the weak nonbonded van der Waals interactions between PZA and SWCNTs. © 2012 Wiley Periodicals, Inc. 相似文献
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A penta‐coordinated Ni(II) complex with a 1,5‐diazacyclooctane (DACO) ligand functionalized by two imidazole donor pendants, [NiL1Cl] (ClO4) H2O (1) (where L1 = 1,5‐bis (imidazol‐4‐ylmethyl)‐l,5‐diazacyclooctane) has been synthesized and characterized by X‐ray diffraction, infrared spectra, elemental analyses, conductance, thermal analyses and UV‐Vis techniques. Complex 1 crystallizes in triclinic crystal system, P‐l space group with a = 0.74782(7), b = 1.15082 (10), c = 1.23781(11) nm, α = 82.090(2), β = 73.011(2), γ = 83.462(2)°, V = 1.00603(16) nm3, M, = 486.00, Z = 2, Dc = 1.604 g/cm3, final R = 0.0435, and wR = 0.1244. The structures of 1 and its related complexes show that in all the three mononuclear complexes, each Ni(II) center is penta‐coordinated with a near regular square pyramid (RSP) to distorted square‐pyramidal (DSP) coordination environment due to the boat/chair configuration of DACO ring in these complexes, and the degree of distortion increases with the augment of the size of the heterocyclic pendants. In addition, the most striking feature of complex 1 resides in the formation of a two‐dimensional network structure through hydrogen bonds and stabilized by π‐π stacking. The solution behaviors of the Ni(II) complexes are also discussed in detail. 相似文献
16.
Synthesis, π‐Face‐Selective Aggregation,and π‐Face Chiral Recognition of Configurationally Stable C3‐Symmetric Propeller‐Chiral Molecules with a π‐Core
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Dr. Nozomi Saito Dr. Ryo Terakawa Prof. Dr. Masahiko Yamaguchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(19):5601-5607
The C3‐symmetric propeller‐chiral compounds (P,P,P)‐ 1 and (M,M,M)‐ 1 with planar π‐cores perpendicular to the C3‐axis were synthesized in optically pure states. (P,P,P)‐ 1 possesses two distinguishable propeller‐chiral π‐faces with rims of different heights named the (P/L)‐face and (P/H)‐face. Each face is configurationally stable because of the rigid structure of the helicenes contained in the π‐core. (P,P,P)‐ 1 formed dimeric aggregates in organic solutions as indicated by the results of 1H NMR, CD, and UV/Vis spectroscopy and vapor pressure osmometry analyses. The (P/L)/(P/L) interactions were observed in the solid state by single‐crystal X‐ray analysis, and they were also predominant over the (P/H)/(P/H) and (P/L)/(P/H) interactions in solution, as indicated by the results of 1H and 2D NMR spectroscopy analyses. The dimerization constant was obtained for a racemic mixture, which showed that the heterochiral (P,P,P)‐ 1 /(M,M,M)‐ 1 interactions were much weaker than the homochiral (P,P,P)‐ 1 /(P,P,P)‐ 1 interactions. The results indicated that the propeller‐chiral (P/L)‐face interacts with the (P/L)‐face more strongly than with the (P/H)‐face, (M/L)‐face, and (M/H)‐face. The study showed the π‐face‐selective aggregation and π‐face chiral recognition of the configurationally stable propeller‐chiral molecules. 相似文献
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Prof. Dr. Tetsuo Okujima Tasuku Kikkawa Prof. Dr. Haruyuki Nakano Hiroshi Kubota Nobumasa Fukugami Prof. Dr. Noboru Ono Prof. Dr. Hiroko Yamada Prof. Dr. Hidemitsu Uno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12854-12863
Bicyclo[2.2.2]octadiene (BCOD) fused azuliporphyrins were synthesized by 3+1 porphyrin synthesis of azulitripyrranes with diformylpyrroles. Subsequent retro‐Diels–Alder reaction of the BCOD‐fused azuliporphyrins afforded azulibenzo‐, azulidibenzo‐, and azulitribenzoporphyrins 1 – 5 . NMR and UV/Vis spectra, as well as nucleus‐independent chemical shift (NICS) calculations revealed that 1 – 5 and their diprotonated dications exhibit relatively low porphyrinoid aromaticity, which was dependent on the position and number of fused benzene rings present. 相似文献
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Manfredo Hrner Adailton Joo Bortoluzzi Johannes Beck Michael Serafin 《无机化学与普通化学杂志》2002,628(5):1104-1107
The reaction of PhN3(H)C6H4N3(H)Ph with Hg(NO3)2 in THF in the presence of triethylamine yields {Hg[PhN3C6H4N3(H)Ph](NO3)} as a yellow powder that can be recrystallized from THF/acetone. The crystals belong to the monoclinic system, space group P21 with the cell dimensions a = 9.639(2), b = 5.412(1), c = 19.675(4) Å, β= 97.47(3)°, V = 1017.7 (4) Å3, Z = 2. The crystal structure determination (2668 unique reflections with [I>2σ(I)], 262 parameters, R1 = 0.0393) shows that the structure consists of mononuclear complexes. Hg atoms are linearly coordinated by one Nα atom of the triazenide unit of the planar ligand [Hg‐N(1) = 2.101(8) Å] and an O atom of the NO3— ion [Hg‐O(1) = 2.11(1) Å]. Additional weak Hg‐N contacts [Hg‐N(4) = 2.662(9) and Hg‐N(3) = 2.851(9) Å] and an intramolecular hydrogen bond between the triazenide hydrogen and an O atom of the nitrate group are observed [N(6)‐H(6)···O(2) = 2.92(2) Å]. The complexes are stacked to infinite chains by metal‐arene π‐interactions. Each Hg atom is coordinated by the terminal phenyl rings of two neighboring complexes [Hg‐C from 3.40(1) to 4.10(1) Å] in a η2 fashion. 相似文献