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1.
Zhang J Xu Z Zong Y Xu Z Chen S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(2):368-370
The NMR and FT-IR spectra of 10 (etaC6H9CRR'-Cp)2MCl2 (M=Ti, Zr) were measured. Results indicate that the metal atom formed bond combination with the center of cyclopentadienyl. NMR spectra move to high field when electronegativity decreases. The electronegativity difference of Ti and Zr mainly influences their IR spectra at the far-infrared range. The characteristic vibrational frequencies of the compounds move to low wave number region with the lower electronegativity. The difference of substituents imposes little effect on the compounds' vibrational frequencies. 相似文献
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M. Spoliti L. Bencivenni A. Farina B. Martini S.Nunziante Cesaro 《Journal of Molecular Structure》1980
The far IR and Raman spectra of gaseous (C5H5)TiCl3 and (C5H5)2MCl2 species (M = Ti, Zr and Hf) are reported. The results are compared to the previous vibrational analysis of the corresponding species in the solid and matrix isolated phases. The assignment of the metal skeletal vibrations is reexamined in further detail on the basis of the new spectroscopic measurements. The torsional frequencies and the related potential barriers are investigated. 相似文献
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G. Balducci L. Bencivenni G. De Rosa R. Gigli B. Martine S.Nunziante Cesaro 《Journal of Molecular Structure》1980
The infrared and Raman spectra of some cyclopentadienyl compounds of the transition metals, namely Ti(C5H5)Cl3 and M(C5H5)2Cl2 (M = Ti, Zr and Hf), are reported and discussed. The infrared spectra of the gaseous species isolated in argon matrices at 10 K provide structural information about the single molecules. Particular attention has been paid to the low-frequency region in order to achieve more reliable assignments for the internal-rotation modes. The structural data and the fundamental frequencies derived from the spectra are employed in a calculation of the thermodynamic functions for these compounds in the ideal gas state. 相似文献
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Z. S. Klemenkova B. V. Lokshin L. I. Strunkina M. Kh. Minacheva 《Russian Chemical Bulletin》1994,43(9):1516-1521
Raman and IR spectra (4000-50 cm–1) of solid cyclopentadienyl zirconium and hafnium hydrides Cp2MH2, Cp2MD2, Cp2Zr(H)X, and Cp2Zr(D)X (Cp = 5-C5H5; M = Zr, Hf; X = Cl, Br) have been studied. The vibrational modes of MH groups, Cp-rings, and metal-ligand bonds are discussed and the band assignments are proposed. In the solid state, these complexes form polymers with linear hydride bridges of the M-H-M type. The force constants of the M-H and M-Cp bonds increase on going from Zr to Hf.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1604–1609, September, 1994. 相似文献
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Chirik PJ 《Dalton transactions (Cambridge, England : 2003)》2007,(1):16-25
The rich chemistry of substituted bis(cyclopentadienyl)zirconium and hafnium complexes bearing side-on coordinated dinitrogen ligands is highlighted in this Perspective. Our studies in this area were initially motivated by the desire to understand side-on vs. end-on dinitrogen coordination in bimetallic zirconocene and hafnocene N2 compounds. In the cases where eta2,eta2-dinitrogen compounds were isolated, both structural and computational data have established significant imido character in the metal-nitrogen bonds. This additional bonding interaction, which is diminished in end-on complexes bearing both terminal and bridging N2 ligands, facilitates dinitrogen functionalization by non-polar reagents including dihydrogen, carbon-hydrogen bonds and weak Br?nsted acids such as water and ethanol. In hafnocene chemistry, where unwanted side-on, end-on isomerization is suppressed, cycloaddition of phenylisocyanate to coordinated N2 has also been accomplished. For N-H bond forming reactions involving H2, kinetic measurements, in addition to isotopic labelling and computational studies, are consistent with dinitrogen functionalization by 1,2-addition involving a highly ordered, four-centred transition structure. 相似文献
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《Journal of organometallic chemistry》1986,307(3):307-317
The He(I) and He(II) photoelectron spectra are reported for two series of transition metal mixed sandwich complexes of general formula LaMLb (M = Ti, La = η5-C5H5, η5-CH3C5H4, η5-C5(CH3)5; M = Zr, Hf, La = η5-C5(CH3)5; Lb = η7-C7H7 (series I); M = Ti, La = η5-CH3C5H4, η5-C5(CH3)5; M = Zr, La = η5-C5(CH3)5; Lb = η8-C8H8 (series II)). Assignments were made of the metal d, cyclopentadienyl and carbocyclic π orbitals on the basis of He(I)/He(II) intensity ratios and shift effects and by comparison with UP data for related compounds. For series I no influence of the central metal upon the IEs of the highest occupied molecular orbital e2 was observed. The IE of the non-bonding metal dz2 orbital of Ti or Zr (5.28 and 4.70 eV, respectively) in the complexes of series II (La = η5-C5(CH3)5) is very low. 相似文献
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(RCp)~2MCl~2, (RCp)TiCl~3分别与N-(4-苯基-2-噻唑基)二硫代氨基甲酸钾和3-苯基-5-(2-呋喃基)-吡唑啉-1-二硫代甲酸钠进行反应, 合成了三十二个未见报道的(RCp)M(S~2CNHR')~nCl~3~-~n,(RCp)~2M-(S~2CNHR')~nCl~2~-~n [R=H, Me; M=Ti, Zr; R'=4-苯基噻唑基(PTDTC), n=1,2,3] 以及(RCp)M(S~2CR^2)~nCl~3~-~n,(RCp)~2M(S~2CR^2)~nCl~2~n[R=H,Me;M=Ti,Zr,R^2=3-苯基-金-(呋喃-2)吡唑啉基(PFPDTC), n=1,2,3]型配合物。所有配合物经元素分析、UV、IR和^1H NMR谱证实, 二硫代氨基甲酸是以双齿配体键合的。 相似文献
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Russian Chemical Bulletin - 相似文献
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Jesús Cano 《Journal of organometallic chemistry》2007,692(21):4448-4459
We present in this account the synthesis and recent developments of a new class of group 4 metal complexes with the tridentate di(silylamido)cyclopentadienyl ligand. These doubly silyl-bridged group 4 metal amido chelates are receiving increasing interest as they are efficient catalysts for ethene polymerization when activated with MAO despite generating 14-electron d0 cationic species free of the alkyl group required for the first insertion reaction in the polymerization process. 相似文献
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V. G. Sevastyanov E. P. Simonenko N. A. Ignatov Yu. S. Ezhov N. P. Simonenko N. T. Kuznetsov 《Russian Journal of Inorganic Chemistry》2011,56(5):661-672
Nanosized refractory titanium, zirconium, and hafnium carbides were manufactured from highly dispersed metal dioxide-carbon
starting mixtures at moderate temperatures of 1200°C or lower. The products were characterized by powder X-ray diffraction,
elemental analysis, and transmission electron microscopy. The average size of particles (in nanometers) manufactured at 1200°C
was as follows: for TiC, 13 ± 4; for ZrC, 17 ± 3; and for HfC, 16 ± 3; the average crystallite size (in nanometers) was as
follows: for TiC, 8 ± 2; for ZrC, 5 ± 2; and for HfC, 8 ± 3. Thermodynamic modeling was performed for the synthesis of Group
IVB carbides via carbothermal reduction of the corresponding oxides. The results show that in the titanium dioxide-carbon
system, for example, titanium monocarbide formation is possible at a temperature as low as 850°C (p = 10−4 MPa). Highly dispersed metal dioxide-carbon starting mixtures were prepared using solgel technology from metal alkoxyacetylacetonates
in the presence of a polymeric carbon source. 相似文献
16.
Charles W. Tullock Frederick N. Tebbe Rolf Mulhaupt Derick W. Ovenall Robert A. Setterquist Steven D. Ittel 《Journal of polymer science. Part A, Polymer chemistry》1989,27(9):3063-3081
Bis(arene) complexes of zerovalent titanium, zirconium, and hafnium supported on partially dehydroxylated, fumed alumina are effective catalysts for the polymerization of olefins. The zerovalent complexes react with surface hydroxyls with loss of one equivalent of arene to yield the active species. The polyethylenes derived from these catalysts are very high molecular weight. Polymerization of propylene yields elastomeric stereoblock polymers which are composed of isotactic and stereoirregular sequences. The polymers are stiffer than polypropylenes obtained with similar catalysts derived from tetra(neophyl)zirconium. The chain microstructures of the various components of the whole polymers have been characterized by 13C-NMR and solvent extraction studies. The ether soluble component of these polymers is of a relatively high molecular weight and the microstructure of the backbone is largely stereoirregular. It is the cocrystallization of this fraction of the polymer with the crystalline, isotactic fractions which is critical to the observed elastomeric properties. 相似文献
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The preparation and characterisation of the Group IVA neopentyls (Me3CCH2)4M (M = Ti, Zr, or Hf) is described. Spectroscopic data (IR, Raman, mass, 1H NMR, and PE) are provided; IR and Raman bands have been assigned by comparison with results on Group IVB analogues (M = Ge or Sn). MC4 stretching vibrations fall in the range 540–485 cm?1, and bending modes at 240–283 cm?1. Thermal decomposition gives neopentane as the sole detectable product; qualitatively, stability increases in the order M = Ti < Zr < Hf and for R4M : R = Me ? Me3CCH2 ≈ Me3SiCH2. (Me3CCH2)4Ti is aerobically oxidised in benzene to give (Me3CCH2O)4Ti 相似文献
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Sandra Taubmann 《Journal of organometallic chemistry》2009,694(13):2005-4547
Metallocene complexes in combination with cocatalysts like methylalumoxane (MAO) are not only excellent catalysts for olefin polymerization but also appropriate catalysts for the activation of alkanes in homogeneous (autoclave) and heterogeneous (fixed bed reactor) reactions. The activities of the catalysts depend on the temperature, the cocatalysts, additives, the central metal and the ligand structure. Generally, complexes with low steric demands and MAO as cocatalyst gave the highest activities. The comparison of different π-ligands resulted in the following activity order: cyclopentadienyl > indenyl > fluorenyl. The influence of σ-ligands and n-donor ligands gave the following activity order: -Cl > -PMe3 > -CH2Ph > -(CH2)4CH3 > -NPh3. The activities depended on the nature of the cocatalyst and decreased in the following order: MAO ? AlMe3 > AlEt3. The addition of aluminum powder and the Lewis base NPh3 increased the activity of the Cp2ZrCl2/MAO catalyst. The Cp2ZrCl2/MAO/NPh3 catalyst showed the highest activity in homogeneous reactions with 458 turnovers in 16 h at 300 °C. The Cp2ZrCl2/MAO/NPh3/SI1102 catalyst gave the highest activity in heterogeneous catalysis with 206 turnovers in 5 h at 350 °C. None of the catalysts required a hydrogen acceptor like an external olefin. 相似文献