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101.
Hitchcock PB Huang Q Lappert MF Zhou M 《Dalton transactions (Cambridge, England : 2003)》2005,(18):2988-2993
The following crystalline oligonuclear metal alkyls have been synthesised under mild conditions and structurally characterised: [(THF)Li(mu-A)(mu-Cl)(mu3-OMe)Zn]2, [Li(mu-A)2Tl]2(4 and 4'), [Li4(mu-A)3(micro3-OMe)]5, [(mu-A)Li2(mu-A)2(mu3-OMe)Ce(A)](6) and [Ce(A)(mu2-OMe){mu2-OS(O)(CF3)O}]2(11)[= CH(SiMe3){SiMe(OMe)2}]. Compounds 2-6 were obtained from [Li(mu-A)]infinity(1) and ZnCl2(3), TlCl (4 and 4' and 5) and CeCl3(6), and 11 was isolated from K(A)(prepared from 1 + KOBu(t)) and cerium(III) triflate Ce(OTf)3. The principal novel features are (i) and (ii) as follows. As for (i), the diversity of ligand-to-metal bonding is noteworthy, the ligand being (a)C,O-bridging in 3{as in the known compounds 1 and in [Li2Mg5(mu3-OMe)6(mu2-OMe)2(mu2-A)4](2)}; (b)C,O,O'-bridging and O,O'-chelating in 4 and 4'; (c)C,O,O'-bridging in 5; (d)C,O,O'-bridging and C,O-chelating in 6; and (e)C,O-chelating in 11. Regarding (ii), it is interesting that the ligand [A]- is surprisingly ready to undergo fragmentation by Si-OMe cleavage and thereby present bridging methoxy ligands (mu2-OMe)2 to a pair of Ce3+ ions in 11, or mu3-OMe acting as a cap for triangular arrays of three hard metal ions (Mg3 in 2, LiZn2 in 3, Li3 in 5, and Li2Ce in 6). 相似文献
102.
A new synthesis of (2S,3R)-[3',3',3'-2H3]-valine has been completed and (2S,3S)-4-fluorovaline has been synthesised for the first time. Both compounds have been prepared by routes involving stereoselective addition to the (S)-pyroglutamate derivative and are available for studies in several areas of bio-organic chemistry. 相似文献
103.
Antolini F Gehrhus B Hitchcock PB Lappert MF 《Chemical communications (Cambridge, England)》2005,(40):5112-5114
Reactions of the silylene Si[(NCH2Bu(t))2C6H4-1,2], [Si(NN)], with NaOMe, excess Na or 1/3 Na yield the X-ray-characterised crystalline compounds [Na(micro-Si(NN)OMe)(THF)(OEt2)]2 (2b), [Na(THF)2Si(NN)]2 (3) and [Na(THF)4][(Si(NN))3-c] (4). 相似文献
104.
G.-S. Kim L. M. Hitchcock F. Siegler E. W. Rothe C. C. Tung G. P. Reck 《Applied physics. B, Lasers and optics》1993,56(3):139-145
Rayleigh scattering and planar laser induced predissociative fluorescence are used to obtain 2-D images of total and specific densities inside a combustion bomb. The experimental arrangement is the same for both methods except for the selection of laser wavelength and the filtering of the radiated light. The former method yields a distribution of total densities while the latter provides densities of hot O2, i.e., those with v=2, J=17 and 33. Hydrogen-air mixtures of various compositions are used. Because the thermodynamics are well known, a bomb may serve as a reference device for diagnostics for high temperature species, and the results are in accord with calculations. Additional Rayleigh experiments are described which yield a) scattering cross sections at 193 nm, b) a 2-D temperature distribution in a hot air stream, and c) a 2-D temperature distribution, of limited precision, inside the bomb. 相似文献
105.
Ala'a K. Abdul-Sada Salih Al-Juaid Anthony M. Greenway Peter B. Hitchcock Matthew J. Howells Kenneth R. Seddon Thomas Welton 《Structural chemistry》1990,1(4):391-394
The crystal and molecular structures of [Me2Etim]Cl, [Me2Etim]2[CoCl4], and [Me2Etim]2[NiCl4] ([Me2Etim]+ = 1,2-dimethyl-3-ethylimidazolium cation) all contain evidence that the H4 and H5 protons of the imidazolium cation enter into hydrogen bonds; the implications of this observation for the interactions in room-temperature chloroaluminate(III) ionic liquids are considered. 相似文献
106.
Avent AG Cloke FG Elvidge BR Hitchcock PB 《Dalton transactions (Cambridge, England : 2003)》2004,(7):1083-1096
Novel yttrium chelating diamide complexes [(Y[ArN(CH(2))(x)NAr](Z)(THF)(n))(y)] (Z = I, CH(SiMe(3))(2), CH(2)Ph, H, N(SiMe(3))(2), OC(6)H(3)-2,6-(t)Bu(2)-4-Me; x = 2, 3; n = 1 or 2; y = 1 or 2) were made via salt metathesis of the potassium diamides (x = 3 (3), x = 2 (4)) and yttrium triiodide in THF (5,10), followed by salt metathesis with the appropriate potassium salt (6-9, 11-13, 15) and further reaction with molecular hydrogen (14). 6 and 11(Z = CH(SiMe(3))(2), x = 2, 3) underwent unprecedented exchange of yttrium for silicon on reaction with phenylsilane to yield (Si[ArN(CH(2))(x)NAr]PhH) (x = 2 (16), 3) and (Si[CH(SiMe(3))(2)]PhH(2)). 相似文献
107.
Anthony G. Avent Christian Drost Barbara Gehrhus Peter B. Hitchcock Michael F. Lappert 《无机化学与普通化学杂志》2004,630(12):2090-2096
Treatment of {HNR}2C10H6‐1, 8 [R = SiMe3 ( 1 ), CH2But ( 2 )] with Sn[N(SiMe3)2]2 afforded the cyclic stannylene Sn[{NR}2C10H6‐1, 8] [R = SiMe3 ( 3 ), CH2But ( 4 )]. From 3 and SnCl2 in THF and crystallisation from toluene, the product was the crystalline tetracyclic compound ( 5 ) as the (toluene)0.5‐solvate. Reaction of 4 with the silylene Si[(NCH2But)2C6H4‐1, 2] ( 6 ) [abbreviated as Si(NN)] in benzene and crystallisation in presence of Et2O furnished the crystalline tricyclic complex Sn[{Si(NCH2But)2C6H4‐1′, 2′}2‐{(NCH2But)2C10H6‐1, 8}] ( 7 ) as the Et2O‐solvate. Complex 5 slowly dissociated into its factors 3 and SnCl2 in toluene, but rapidly in THF. Solutions of 7 in C6D6, C7D8 or THF‐d8, studied by multinuclear, variable temperature NMR spectroscopy, revealed the presence of an equilibrium between 8 (an isomer of 7 , in which the skeletal atoms of the eight‐membered ring were , rather than the of 7 ) and 4 + 2 Si(NN), with 8 dominant in PhMe but not in THF; additionally 8 was shown to be fluxional and solutions of 8 in C6D6 or C7D8 decomposed to give the silane Si(NN)[(NCH2But)2C10H6‐1, 8], 6 and Sn metal. The X‐ray structures of 3 , 5 and 7 are presented. 相似文献
108.
Ruiz J Martínez MT Rodríguez V López G Pérez J Chaloner PA Hitchcock PB 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3521-3527
Heating a suspension of the monomeric hydroxo palladium complex of the type [Pd(N-N)(C(6)F(5))(OH)](N-N = bipy, Me(2)bipy, phen or tmeda) in methylketone (acetone or methylisobutylketone) under reflux affords the corresponding ketonyl palladium complex [Pd(N-N)(C(6)F(5))(CH(2)COR)]. On the other hand, the reaction of the hydroxo palladium complexes [Pd(N-N)(C(6)F(5))(OH)](N-N = bipy, phen or tmeda) with diethylmalonate or malononitrile yields the C-bound enolate palladium complexes [Pd(N-N)(CHX(2))(C(6)F(5))](X = CO(2)Et or CN), and the reaction of [Pd(N-N)(C(6)F(5))(OH)](N-N = bipy or phen) with nitromethane gives the nitromethyl palladium complexes [Pd(N-N)(CH(2)NO(2))(C(6)F(5))]. [Pd(tmeda)(C(6)F(5))(OH)] catalyses the cyclotrimerization of malononitrile. The crystal structures of [Pd(bipy)(C(6)F(5))(CH(2)COMe)].1/2Me(2)CO, [Pd(tmeda)(C(6)F(5))[CH(CO(2)Et)(2)]], [Pd(tmeda)(C(6)F(5))[CH(CN)(2)]] and [Pd(tmeda)(C(6)F(5))(CH(2)NO(2))].1/2CH(2)Cl(2) have been established by X-ray diffraction. 相似文献
109.
Hill MS Hitchcock PB Pongtavornpinyo R 《Dalton transactions (Cambridge, England : 2003)》2005,(2):273-277
The neutral monovalent Group 13 beta-diketiminato complexes [CH{(CF3)2CN-2,6-iPr2C6H3}2In] and [CH{(Me)2CN-2,6-iPr2C6H3}2Tl] have been synthesised by analogous 'one-pot' procedures involving reaction of [KN(SiMe3)2] with the appropriate beta-imino-enamine and Group 13 iodide. The structure of the indium complex reveals that replacement of the ligand backbone methyl groups of the previously reported complex [CH{(Me)2CN-2,6-iPr2C6H3}2In] with trifluoromethyl substituents results in only minor modifications to the dimensions of the NCCCNIn metallacycle. The electronic structures of both indium species were interrogated by DFT calculations to reveal similar frontier molecular orbital schemes. In agreement with calculations performed previously on the aluminium and gallium complexes, [CH{(Me)2CN-2,6-iPr2C6H3}2Al] and [CH{(Me)2CN-2,6-iPr2C6H3}2Ga], the HOMO in both indium species comprises a metal-based sp-hybrid while the LUMO is a ligand-based orbital of pi symmetry. The vacant indium p-orbital is represented by the LUMO + 1. Although incorporation of the fluorinated substituents results in a stabilisation of the system overall, the stabilities and observed structural features of the complexes are reasoned to be primarily a result of the steric profile of the very bulky ligands and not through any redistribution of the electron density within the cyclic species. The thallium complex is isostructural to the analogous and previously reported aluminium, gallium and indium species. The greater stability of the monovalent state however is reflected in a reordering of the orbital energies and a stabilisation of the metal-based orbitals in the frontier region of the MO scheme. 相似文献
110.
Clentsmith GK Gibson VC Hitchcock PB Kimberley BS Rees CW 《Chemical communications (Cambridge, England)》2002,(14):1498-1499
Addition of MeLi to bis(imino)pyridines results in an unprecedented nucleophilic attack at pyridine nitrogen to afford novel mono-anionic [N,N,N] ligands: their treatment with FeCl3, followed by MAO activation, affords highly active ethylene polymerisation catalysts. 相似文献