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51.
Hitchcock PB Lappert MF Protchenko AV 《Chemical communications (Cambridge, England)》2005,(7):951-953
Attempted synthesis of sterically demanding bis- or tris-beta-diketiminato complexes of lanthanoids resulted in ligand deprotonation and the formation of complexes containing both a "normal" and a deprotonated ligand; one of these on protonation gave the first cationic beta-diketiminato-Ln complex. 相似文献
52.
A.P. Hitchcock C.E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1980,19(2):231-250
Excitation and ionisation of the carbon and oxygen 1s electrons of formaldehyde, acetaldehyde and acetone have been examined by small-angle inelastic scattering of 2.5-keV electrons, with energy resolutions in the range 0.20–0.50 eV FWHM. Features in the electron energy loss spectra below the inner-shell ionisation thresholds have been assigned to transitions to unoccupied valence (π*) and Rydberg orbitals. Broad maxima in the inner-shell continua of all three molecules have been interpreted as resonances associated with transitions to σ*(CO) orbitals. The assignments of the acetaldehyde and acetone spectra have been supported by comparison with those for CH4 and H2 CO. The adiabatic first ionisation potential of H2 NO and H2 CF have been estimated from the inner-shell spectra of formaldehyde using the equivalent-core analogy. 相似文献
53.
Two alternative "ring switch" based syntheses have been shown to give access to the reduced protected homochiral analogues, 27, 28 and 36, of the CNS active compound ibotenic acid. 相似文献
54.
Hill MS Pongtavornpinyo R Hitchcock PB 《Chemical communications (Cambridge, England)》2006,(35):3720-3722
Modulation of the steric requirements of a number of N-aryl beta-diketiminate ligands results in the isolation of a variety of Tl(I) compounds with different stabilities and nuclearities. 相似文献
55.
We measure the effect of a magnetic Feshbach resonance (FR) on the rate and light-induced frequency shift of a photoassociation resonance in ultracold 7Li. The photoassociation-induced loss-rate coefficient K_{p} depends strongly on magnetic field, varying by more than a factor of 10;{4} for fields near the FR. At sufficiently high laser intensities, K_{p} for a thermal gas decreases with increasing intensity, while saturation is observed for the first time in a Bose-Einstein condensate. The frequency shift is also strongly field dependent and exhibits an anomalous blueshift for fields just below the FR. 相似文献
56.
Angela C. Raimondi Peter B. Hitchcock G. Jeffery Leigh Fábio S. Nunes 《Journal of chemical crystallography》2004,34(2):83-87
The crystal structure of the binuclear tetraiminediphenolate diiron(II) macrocyclic complex [Fe2(tidf)(CH3OH)4](ClO4)2 (tidf = tetraiminediphenolate ligand) is presented. The molecular structure (monoclinic, space group C2/c, Z = 4, a = 20.6903(14)Å, b = 11.0827(11) Å, c = 16.0494(15) Å, = 99.911(6) shows two iron(II) cores occupying distorted octahedral geometries with four methanol molecules bound axially. Main equatorial bond distances are 2.050(3) Å for Fe—O1 and 2.067(4) Å for Fe—N1 with a Fe Fe distance of 3.108(1) Å. Contrasting to the monoiron complex the macrocycle does not adopt a bent conformation being nearly coplanar with the maximum deviation from the least-squares plane of 0.18 Å. 相似文献
57.
Khalaf MS Coles MP Hitchcock PB 《Dalton transactions (Cambridge, England : 2003)》2008,(32):4288-4295
Partial deprotonation of the bicyclic guanidine 1,4,6-triazabicyclo[3.3.0]oct-4-ene (Htbo) is achieved using (n)BuLi. Isolation of the resulting lithium salts has resulted in the structural characterization of the mixed anion complex {[Li(tbo)()(tboH)](2)}(infinity) (where -H = 1-(2-aminoethyl)-2-imidazolidinethione) and the partially deprotonated salt Li(6)(tbo)(6)(Htbo)(3), . The neutral guanidine Htbo reacts cleanly with AlMe(3) and ZnMe(2) to afford the organometallic complexes [Al(tbo)Me(2)](2) [](2), and Zn(3)(tbo)(4)Me(2) (). Structural characterization of these compounds enables comparison between the {5:5}-bicyclic system, [tbo](-), and the previously reported {6:6}-bicyclic system, [hpp](-) (where hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine). Results indicate that delocalization within the [tbo](-) anion is restricted to the CN(2) amidinate component, with retention of electron density in the non-bonding nitrogen lone-pair. These conclusions are supported by a DFT analysis of the neutral guanidines, Htbo and hppH. 相似文献
58.
Barrett AG Crimmin MR Hill MS Hitchcock PB Procopiou PA 《Dalton transactions (Cambridge, England : 2003)》2008,(33):4474-4481
A series of heteroleptic beta-diketiminate-stabilised calcium amides of the form [{ArNC(Me)CHC(Me)NAr}Ca{NR(1)R(2)}(THF)] (Ar = 2,6-diisopropylphenyl; R(1) = H, R(2) = Ar; R(1) = H, R(2) = CH(2)CH(2)OMe; R(1) = R(2) = Ph) react with 1,3-dialkylcarbodiimides, R(3)N[double bond, length as m-dash]C[double bond, length as m-dash]NR(3) (R(3) = Cy, (i)Pr), to yield the corresponding insertion products [{ArNC(Me)CHC(Me)NAr}Ca{(R(3)N)(2)CNR(1)R(2)}(THF)] at room temperature in hydrocarbon solutions. These latter compounds contain both beta-diketiminate and guanidinate ligands bound to calcium. Solid-state data are consistent with the guanidinate ligands adopting a number of binding modes including kappa(2) through kappa(3) coordination, with varying degrees of delocalisation of the non-bound guanidinate nitrogen lone-pair across the pi-framework of the ligand. DFT computational studies have been conducted to address these variations in coordination behaviour. 相似文献
59.
Raleigh W. Parrott II Christopher G. Hamaker Shawn R. Hitchcock 《Journal of heterocyclic chemistry》2008,45(3):873-878
A series of oxazolidines have been prepared by condensation of N‐isopropyl norephedrine with a variety of salicylaldehyde derivatives. Despite the stereochemical relationship of (1R,2S)‐norephedrine with (1R,2S)‐ephedrine, the resultant oxazolidines 12‐14 were determined to have a stronger stereochemical relationship with (1S,2S)‐pseudoephedrine based oxazolidines. The resultant oxazolidines were used as catalytic ligands in the addition of diethylzinc to several aldehydes. It was determined that the oxazolidine derivative 12 gave the highest yield and a moderate enantioselectivity. 相似文献
60.
Phospha(III)guanidines, R2PC{NR'}{NHR'}, have been used to synthesize multimetallic compounds containing combinations of aluminum with platinum or copper, in which the main-group metal is N,N'-bound by an amidinate moiety, thereby generating a metal-functionalized phosphine that bonds to the transition metal through phosphorus. 相似文献