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1.
The molybdenum and tungsten complexes W2(NtBu)4(pz)4(pzH).(C6H14)0.5 (pz = pyrazolate), M(NtBu)2(Me2pz)2(Me2pzH)2 (Me2pz = 3,5-dimethylpyrazolate), M(NtBu)2(tBu2pz)2 (tBu2pz = 3,5-di-tert-butylpyrazolate), M2(NtBu)4(Me2pz)2Cl2, W(NtBu)2(C2N3(iPr)2)2py2, M(NtBu)2-(CN4CF3)2py2, and W(NtBu)2(PhNNNPh)2 were prepared by various synthetic routes from the starting materials Mo(NtBu)2Cl2, W(NtBu)2(NHtBu)2, and W(NtBu)2Cl2py2. These new complexes were characterized by spectral and analytical methods and by X-ray crystal structure determinations. The volatilities and thermal stabilities were evaluated to determine the potential of the new complexes for use in thin film growth of metal nitride films. Mo(NtBu)2(tBu2pz)2 and W(NtBu)2(tBu2pz)2 were found to have the optimum combination of volatility and thermal stability for application in atomic layer deposition thin film growth procedures. 相似文献
2.
The present note deals with the effects of radiative heat transfer and free convection in MHD for a flow of an electrically
conducting, incompressible, dusty viscous fluid past an impulsively started vertical non-conducting plate, under the influence
of transversely applied magnetic field. The heat due to viscous dissipation and induced magnetic field is assumed to be negligible.
The governing linear partial differential equations are solved by finite difference technique. The effects of various parameters
(like radiation parameter N, Prandtl number Pr, porosity parameter K) entering into the MHD Stokes problem for flow of dusty conducting fluid have been examined on the temperature field and
velocity profile for both the dusty fluid and dust particles. 相似文献
3.
Dezelah CL El-Kadri OM Szilágyi IM Campbell JM Arstila K Niinistö L Winter CH 《Journal of the American Chemical Society》2006,128(30):9638-9639
The atomic layer deposition of W2O3 films was demonstrated employing W2(NMe2)6 and water as precursors with substrate temperatures between 140 and 240 degrees C. At 180 degrees C, surface saturative growth was achieved with W2(NMe2)6 vapor pulse lengths of >/=2 s. The growth rate was about 1.4 A/cycle at substrate temperatures between 140 and 200 degrees C. Growth rates of 1.60 and 2.10 A/cycle were observed at 220 and 240 degrees C, respectively. In a series of films deposited at 180 degrees C, the film thicknesses varied linearly with the number of deposition cycles. Time-of-flight elastic recoil analyses demonstrated stoichiometric W2O3 films, with carbon, hydrogen, and nitrogen levels between 6.3 and 8.6, 11.9 and 14.2, and 4.6 and 5.0 at. %, respectively, at substrate temperatures of 160, 180, and 200 degrees C. The as-deposited films were amorphous. Atomic force microscopy showed root-mean-square surface roughnesses of 0.7 and 0.9 nm for films deposited at 180 and 200 degrees C, respectively. The resistivity of a film grown at 180 degrees C was 8500 microhm cm. 相似文献
4.
The synthesis, solid-state structure, and solution structure of Cr2(tBu2pz)4 are described. This complex is obtained by sublimation of the monomeric species Cr(tBu2pz)2(4-tBupy)2 and contains long chromium-chromium distances that are enforced by the divergent nature of the pyrazolato ligands. 相似文献
5.
Abstract— The properties of a pulsed ruby laser beam focused through a triocular microscope were studied in relation to microsurgery. Quantitative studies on 'model tissues' with different absorbencies at 6943 Å revealed that the spot diameter of the focused microbeam was dependent upon several factors. It decreased with (1) a decrease in the absorption by the object at 6943 Å; (2) a decrease in the energy of the microbeam; and (3) an increase in the magnification of the microscope. The existence of the 'tube of effect' in the optical path of the focused micro-beam was realized by irradiating the object at different planes. The depth of the tube of effect increased with (1) increase in laser energy or (2) decrease in magnification. By employing certain plant species ( Spirogyra praetensis Transeau, Ulva lactuca Linnaeus, Porphyra miniata (Lyngbye) C. Agardh and Elodea sp.) the reaction of the protoplasm to the laser microbeam in terms of 'primary damage' and 'secondary damage' was defined. Based on these experimental data the concept of minimal visible spot size in laser microsurgery and its limitations are discussed. 相似文献
6.
Oussama M. El-Kadri 《Journal of organometallic chemistry》2009,694(24):3902-2564
Treatment of M(allyl)(Cl)(CO)2(py)2 (M = Mo, W) with 1 equiv. of potassium pyrazolates in tetrahydrofuran at −78 °C afforded M(allyl)(R2pz)(CO)2(py)n (R2pz = 3,5-disubstituted pyrazolate; n = 1, 2) in 68-81% yields. X-ray crystal structure analyses of Mo(allyl)((CF3)2pz)(CO)2(py)2 and W(allyl)(tBu2pz)(CO)2(py) revealed η1- and η2-coordination of the (CF3)2pz and tBu2pz ligands, respectively. Analogous treatment of Mo(allyl)(Cl)(CO)2(NCCH3)2 with 1 equiv. of tBu2pzK in tetrahydrofuran at −78 °C afforded [Mo(allyl)(tBu2pz)(CO)2]2 in 79% yield. An X-ray crystal structure analysis of [Mo(allyl)(tBu2pz)(CO)2]2 showed a dimeric structure bridged by two μ-η2:η1-tBu2pz ligands. Treatment of M(allyl)(Cl)(CO)2(py)2 with 1 equiv. of lithium 1,3-diisopropylacetamidinate or lithium 1,3-di-tert-butylacetamidinate in diethyl ether at −78 °C afforded M(allyl)(iPrNC(Me)NiPr)(CO)2(py) and M(allyl)(tBuNC(Me)NtBu)(CO)2(py), respectively, in 68-78% yields. The new complexes were characterized by spectral and analytical methods and by X-ray crystal structure determinations. M(allyl)(iPrNC(Me)NiPr)(CO)2(py) adopt pseudo-octahedral geometry about the metal centers, with the 1,3-diisopropylacetamidate ligand nitrogen atoms spanning one axial site and one equatorial site of the octahedron. By contrast, M(allyl)(tBuNC(Me)NtBu)(CO)2(py) adopt pseudo-octahedral structures in which the two 1,3-di-tert-butylacetamidinate ligand nitrogen atoms span two equatorial coordination sites. Sublimation of M(allyl)(tBuNC(Me)NtBu)-(CO)2(py) at 105 °C/0.03 Torr afforded ?7% yields of M(allyl)(tBuNC(Me)NtBu)(CO)2, along with sublimed M(allyl)(tBuNC(Me)NtBu)(CO)2(py). W(allyl)(tBuNC(Me)NtBu)(CO)2 exists in the solid state as a 16-electron complex with distorted square pyramidal geometry. Many of the new complexes undergo dynamic ligand site exchange in solution, and these processes were probed by variable temperature 1H NMR spectroscopy. The volatilities and thermal stabilities were evaluated to determine the potential of the new complexes for use as precursors in thin film growth experiments. 相似文献
7.
Treatment of anhydrous chromium(III) chloride with 2 or 3 equivalents of 1,3-di-tert-butylacetamidinatolithium or 1,3-diisopropylacetamidinatolithium in tetrahydrofuran at ambient temperature afforded Cr(tBuNC(CH3)NtBu)2(Cl)(THF) and Cr(iPrNC(CH3)NiPr)3 in 78% and 65% yields, respectively. Treatment of Cr(tBuNC(CH3)NtBu)2(Cl)(THF) with the potassium salts derived from pyrazoles and 1,2,4-triazoles afforded Cr(tBuNC(CH3)NtBu)2(X), where X=3,5-disubstituted pyrazolato or 3,5-disubstituted 1,2,4-triazolato ligands, in 65-70% yields. X-Ray crystal structure analyses of Cr(tBuNC(CH3)NtBu)2(Me2pz) (Me2pz=3,5-dimethylpyrazolato) and Cr(tBuNC(CH3)NtBu)2(Me2trz) (Me2trz=3,5-dimethyl-1,2,4-triazolato) revealed eta2-coordination of the Me2pz and Me2trz ligands. Treatment of Cr(tBuNC(CH3)NtBu)2(Cl)(THF) with trifluoromethyltetrazolatosodium (NaCF3tetz) in the presence of 4-tert-butylpyridine afforded Cr(tBuNC(CH3)NtBu)2(CF3tetz)(4-tBupy) in 30% yield. An X-ray crystal structure determination showed eta1-coordination of the tetrazolato ligand through the 2-nitrogen atom. The complexes Cr(iPrNC(CH3)NiPr)3 and Cr(tBuNC(CH3)NtBu)2(X) are volatile and sublime with <1% residue between 120 and 165 degrees C at 0.05 Torr. In addition, these complexes are thermally stable at >300 degrees C under an inert atmosphere such as nitrogen or argon. Due to the good volatility and high thermal stability, these new compounds are promising precursors for the growth of chromium-containing thin films using atomic layer deposition. 相似文献
8.
This paper deals with the adaptive control problem of the unforced generalized Korteweg?Cde Vries?CBurgers (GKdVB) equation when the spatial domain is [0,1]. Three adaptive control laws are designed for the GKdVB equation when either the kinematic viscosity ?? or the dynamic viscosity ?? is unknown, or when both viscosities ?? and ?? are unknowns. Using the Lyapunov theory, the L 2-global exponential stability of the solutions of this equation is shown for each of the proposed control laws. Also, numerical simulations based on the Finite Element method (FEM) are given to illustrate the analytical results. 相似文献
9.
The paper investigates the effects of heat transfer in MHD flow of viscoelastic stratified fluid in porous medium on a parallel plate channel inclined at an angle θ. A laminar convection flow for incompressible conducting fluid is considered. It is assumed that the plates are kept at different temperatures which decay with time. The partial differential equations governing the flow are solved by perturbation technique. Expressions for the velocity of fluid and particle phases, temperature field, Nusselt number, skin friction and flow flux are obtained within the channel. The effects of various parameters like stratification factor, magnetic field parameter, Prandtl number on temperature field, heat transfer, skin friction, flow flux, velocity for both the fluid and particle phases are displayed through graphs and discussed numerically. 相似文献
10.
Oussama M. El-Kadri 《Journal of organometallic chemistry》2011,696(10):1975-1981
Treatment of Cb∗Co(CO)2I (Cb∗ = η4-C4Me4) with one equivalent of potassium 3,5-dimethylpyrazolate (Me2pzK) or potassium 3,5-bis(trifluoromethyl)pyrazolate ((CF3)2pzK) in tetrahydrofuran at 0 °C afforded (η4-C4Me4(Me2pz))Co(CO)2 and Cb∗Co((CF3)2pz)(CO)2 in 90 and 71% yields, respectively. Treatment of Cb∗Co(CO)2I with one equivalent of Me2pzH followed by the addition of one equivalent Me2pzK in tetrahydrofuran afforded Cb∗Co(Me2pzH)(Me2pz)(CO) in 74% yield. The reaction of Cb∗Co(CO)2I with one equivalent of potassium phenyl tetrazolate (PhtetzK) in tetrahydrofuran at 0 °C afforded [Cb∗Co(Phtetz)(CO)]2 in 44% yield. The solid state structure of (η4-C4Me4(Me2pz))Co(CO)2 revealed nucleophilic addition of a pyrazolate nitrogen atom to a Cb∗ ligand carbon atom to afford a novel tetradentate ligand that bonds to the cobalt ion through an η3-π-allyl interaction and one pyrazolyl nitrogen atom. Two carbonyl ligands are also present. An X-ray crystal structure determination of Cb∗Co((CF3)2pz)(CO)2 showed η1-coordination of the (CF3)2pz ligand and η4-coordination of the Cb∗ ligand. The solid state structure of Cb∗Co(Me2pz)(Me2pzH)(CO) is monomeric with one η1-Me2pz, one η1-Me2pzH, two carbonyl, and one η4-Cb∗ ligands. The η1-Me2pz and η1-Me2pzH ligands are linked by a hydrogen bond involving the uncoordinated nitrogen atoms. The X-ray crystal structure determination of [Cb∗Co(Phtetz)(CO)]2 showed a dimeric molecular structure with two μ:η1,η1-Phtetz ligands connected to the cobalt ions through the 2- and 3-nitrogen atoms, one η4-Cb∗ ligand, and one carbonyl ligand per cobalt center. (η4-C4Me4(Me2pz))Co(CO)2 is highly volatile and sublimes at 60 °C/0.03 Torr. 相似文献