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Quantitative characteristics of changes in the energy of charge transfer from -bonded ligands to metal are presented for the series of structurally similar ansa-metallocene complexes of IVB Group elements. The changes are caused by the solvation effect, replacement of -bonded chlorine ligands by methyl groups and of bridging ethylene groups by dimethylsilylene moieties, introduction of the methyl substituent into position 2 and phenyl substituent into position 4 of the indenyl system, variation of the transition metal in metallocene, and formation of complexes with polymethylalumoxane (MAO) at different AlMAO/Zr ratios. These effects are found to be additive.  相似文献   
2.
The products of the reactions of polymethylalumoxane (MAO) with triisobutylaluminum (TIBA), rac-Me2Si(2-Me,4-PhInd)2ZrCl2 (1) with MAO (1 + MAO), and (1 + MAO) + TIBA were studied by 1H NMR at different molar ratios of the components. When the ratio AlTIBA/AlMAO is ∼6, the reaction between MAO and TIBA involves the replacement of the methyl group of MAO by isobutyl groups and the formation of isobutylmethylalumoxane or mixed isobutylmethylalumoxane structures. When the TIBA content in the system increases to 30 mol.%, these structures are rearranged to form products with a low degree of association. With the equimolar ratio of the reactants, the main reaction products are tetraisobutylalumoxane and polyisobutylalumoxane. The 1 + MAO system with the molar ratio AlMAO/Zr = 50 affords a MAO-bonded monomethyl monochloride derivative [L2ZrCl-μ-Me]δ+[MAO]δ−. An increase in this ratio to 150 produces intermediate binuclear complexes [L2ZrCl-μ-Me-MeZrL2]+[MAO] and [Me2Al-(μ-Me)2-ZrL2]+[MAO]. The addition of TIBA induces the replacement of the ZrMe groups by isobutyl groups at the first step of the interaction and formation of nonidentified reaction products at the subsequent steps. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 934–940, April, 2005.  相似文献   
3.
The rates of ethylene polymerization catalyzed by Cp2ZrCl2-polymethylalumoxane and (Cp2ZrCl)2O-polymethylalumoxane are equal. According to NMR and ESR spectral data, the same precatalyst, presumably Cp2ZrMe2, is formed in both systems by the action of AlMe3. This accounts for the equal catalytic activity of the systems based on Cp2ZrCl2 and (Cp2ZrCl)2O. A scheme of reactions resulting in cleavage of the Zr-O-Zr bridge is proposed and confirmed by spectroscopic data.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2104–2107, December, 1993.  相似文献   
4.
Transformation of electronic absorption spectra of zirconocene catalytic systems Ph2CCpFluZrCl2-polymethylalumoxane (MAO) and rac-Me2Si(2-Me,4-PhInd)2ZrCl2-MAO (Flu is fluorenyl, Ind is indenyl) in toluene was studied upon a change in the ratio of reactants AlMAO/Zr from 0 to 3000 mol mol−1. Analysis of the spectroscopic data using statistical methods determined the number of reaction products in each system. A reaction model including three equilibria and being common for the both systems was proposed. Effective equilibrium constants and absorption spectra of individual reaction products were determined by parametric self-modeling of the experimental spectra. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2257–2264, October, 2005.  相似文献   
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