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1.
The major product from 2,3-naphthoquinodimethane formed by cyclisation of -dipropadienylbenzene was found to be the dimer 5 containing an eight-membered ring, for which the inversion barrier was determined by dynamic 1H NMR spectrometry, ΔG3 = 18 kcal/mole. 相似文献
2.
Becerra R Bowes SJ Ogden JS Cannady JP Almond MJ Walsh R 《The journal of physical chemistry. A》2005,109(6):1071-1080
Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with NO. The reaction was studied in the gas phase over the pressure range 1-100 Torr in SF6 bath gas at five temperatures in the range 299-592 K. The second-order rate constants at 10 Torr fitted the Arrhenius equation log(k/cm3 molecule(-1) s(-1)) = (-11.66 +/- 0.01) + (6.20 +/- 0.10 kJ mol(-1))/RT ln 10 The rate constants showed a variation with pressure of a factor of ca. 2 over the available range, almost independent of temperature. The data could not be fitted by RRKM calculations to a simple third body assisted association reaction alone. However, a mechanistic model with an additional (pressure independent) side channel gave a reasonable fit to the data. Ab initio calculations at the G3 level supported a mechanism in which the initial adduct, bent H2SiNO, can ring close to form cyclo-H2SiNO, which is partially collisionally stabilized. In addition, bent H2SiNO can undergo a low barrier isomerization reaction leading, via a sequence of steps, ultimately to dissociation products of which the lowest energy pair are NH2 + SiO. The rate controlling barrier for this latter pathway is only 16 kJ mol(-1) below the energy of SiH2 + NO. This is consistent with the kinetic findings. A particular outcome of this work is that, despite the pressure dependence and the effects of the secondary barrier (in the side reaction), the initial encounter of SiH2 with NO occurs at the collision rate. Thus, silylene can be as reactive with odd electron molecules as with many even electron species. Some comparisons are drawn with the reactions of CH2 + NO and SiCl2 + NO. 相似文献
3.
Katharine F. Bowes George Ferguson Christopher Glidewell John N. Low Antonio Quesada 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(9):o551-o554
N,N′‐Dithiobisphthalimide crystallizes from nitrobenzene solution as a solvate, 2C16H8N2O4S2·C6H5NO2, having space group Pn. The bisphthalimide molecules are linked by C—H?O hydrogen bonds and by aromatic π–π‐stacking interactions, forming a framework enclosing continuous channels running along the [100] direction and accounting for ca 20% of the unit‐cell volume. The nitrobenzene molecules lie in these channels, ordered in a head‐to‐tail fashion and linked to the bisphthalimide framework by C—H?O and C—H?π(arene) hydrogen bonds. 相似文献
4.
Arylspiroborates Derived from 4‐tert‐Butylcatechol and 3,5‐Di‐tert‐butylcatechol and Their Antimicrobial Activities 下载免费PDF全文
Michael I. Webb Nathan R. Halcovitch Eric G. Bowes Graham M. Lee Michael J. Geier Christopher M. Vogels Taryn O'Neill Haoxin Li Andrew Flewelling Andreas Decken Christopher A. Gray Stephen A. Westcott 《Journal of heterocyclic chemistry》2014,51(1):157-161
A family of arylspiroborates has been prepared by the addition of either 4‐tert‐butylcatechol or 3,5‐di‐tert‐butylcatechol to boric acid and an alkali metal hydroxide. All compounds were characterized fully using multinuclear NMR spectroscopy and by elemental analyses. A single crystal X‐ray diffraction was carried out on potassium (bis‐(3,5‐di‐tertbutyl[1,2‐benzenediolato(2‐)‐O,O′]borate)) ( 8 ). All compounds displayed appreciable anti‐microbial activities. 相似文献
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6.
Graham M. Lee Eric G. Bowes Christopher M. Vogels Andreas Decken Stephen A. Westcott 《Tetrahedron》2019,75(14):2106-2112
In this study we have studied the synthesis, characterization and catalytic activity of phosphinocopper(I) complexes [Cu(PPh3)3(NCCH3)][B(O2C6H4-4-R)2] (3a: R?=?H; 3b: R?=?Me; 3c: R?=?NO2) and [Cu(PPh3)3(NCCH3)][B(O2C6H3-3,5-di-tBu)2] (3d) containing weakly coordinating arylspiroborate ligands bearing various electronic and sterically defined characteristics. All new compounds have been characterized fully including single crystal X-ray diffraction studies for 3a and 3c and confirm that the arylspiroborate ligands do not coordinate to the copper atoms. Using these new metal complexes as precatalysts in the cyclisation of short chain alkynoic acids gave the corresponding exo-dig cyclic lactones exclusively. 相似文献
7.
Courtney C. Roberts Nicole M. Camasso Eric G. Bowes Melanie S. Sanford 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(27):9202-9206
Described is a systematic comparison of factors impacting the relative rates and selectivities of C(sp3)?C and C(sp3)?O bond‐forming reactions at high‐valent Ni as a function of oxidation state. Two Ni complexes are compared: a cationic octahedral NiIV complex ligated by tris(pyrazolyl)borate and a cationic octahedral NiIII complex ligated by tris(pyrazolyl)methane. Key features of reactivity/selectivity are revealed: 1) C(sp3)?C(sp2) bond‐forming reductive elimination occurs from both centers, but the NiIII complex reacts up to 300‐fold faster than the NiIV, depending on the reaction conditions. The relative reactivity is proposed to derive from ligand dissociation kinetics, which vary as a function of oxidation state and the presence/absence of visible light. 2) Upon the addition of acetate (AcO?), the NiIV complex exclusively undergoes C(sp3)?OAc bond formation, while the NiIII analogue forms the C(sp3)?C(sp2) coupled product selectively. This difference is rationalized based on the electrophilicity of the respective M?C(sp3) bonds, and thus their relative reactivity towards outer‐sphere SN2‐type bond‐forming reactions. 相似文献
8.
Bowes KF Cole JM Husheer SL Raithby PR Savarese TL Sparkes HA Teat SJ Warren JE 《Chemical communications (Cambridge, England)》2006,(23):2448-2450
The structure of a new metastable geometric isomer of [Ru(NH3)4(H2O)(SO2)][MeC6H4SO3]2 in which the SO2 group is coordinated through a single oxygen in an eta1-OSO bonding mode has been determined at 13 K; the new isomer was obtained as a 36% component of the structure within a single crystal upon irradiation using a tungsten lamp. 相似文献
9.
Katharine F. Bowes George Ferguson Christopher Glidewell Alan J. Lough John N. Low Choudhury M. Zakaria 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(6):o347-o350
N,N′‐Dithiobisphthalimide crystallizes from 1,4‐dioxan solution as a solvate, 3C16H8N2O4S2·1.8C4H8O2, having space group C2/c. Four of the 12 C16H8N2O4S2 molecules in the unit cell lie on twofold rotation axes, while the other eight lie in general positions. These molecules are linked by aromatic π–π‐stacking interactions and by C—H?O hydrogen bonds to form a framework enclosing continuous channels running parallel to the [101] direction, which account for ca 20% of the unit‐cell volume. The dioxan molecules lie in these channels disordered across two sets of sites, with one set across an inversion centre and the other across a twofold rotation axis. 相似文献
10.
Katharine F. Bowes Christopher Glidewell John N. Low 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):o409-o415
The structure of tetrameric triphenylsilanol, C18H16OSi, (I), has been re‐investigated at 120 (2) K. The hydroxyl H atoms were readily located and one of the arene rings is disordered over two closely positioned sets of sites. The molecules are linked into cyclic tetramers, having approximate (S4) symmetry, via O—H?O hydrogen bonds [H?O 1.81–1.85 Å, O?O 2.634 (3)–2.693 (3) Å and O—H?O 156–166°]. At ambient temperature, there are indications of multiple disorder of the phenyl‐ring sites. In bis(triphenylsilanol) dimethyl sulfoxide solvate, 2C18H16OSi·C2H6OS, (II), the dimethyl sulfoxide component is disordered across a twofold rotation axis in C2/c, and the molecular components are linked by a single O—H?O hydrogen bond [H?O 1.85 Å, O?O 2.732 (2) Å and O—H?O 172°] into three‐molecule aggregates, which are themselves linked into a single three‐dimensional framework by two C—H?π(arene) interactions. In tetrakis(triphenylsilanol) 1,4‐dioxan solvate, 4C18H16OSi·C4H8O2, (III), the 1,4‐dioxan component lies across an inversion centre in space group P and centrosymmetric five‐molecule aggregates are linked by paired C—H?π(arene) interactions to form molecular ladders. 相似文献