Lanthanide Metallocene Reactivity with Dialkyl Aluminum Chlorides: Modeling Reactions Used to Generate Isoprene Polymerization Catalysts
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- 作者：William J. Evans ; Timothy M. Champagne ; Dimitrios G. Giarikos ; and Joseph W. Ziller
- 刊名：Organometallics
- 出版年：2005
- 出版时间：February 14, 2005
- 年：2005
- 卷：24
- 期：4
- 页码：570 - 579
- 全文大小：262K
- 年卷期：v.24,no.4(February 14, 2005)
- ISSN：1520-6041
文摘
The well-defined coordination environment of trivalent [(C5Me5)2Ln]+ complexes has beenused to examine the reaction chemistry of the lanthanide carboxylate and R2AlCl (R = Me,Et, iBu) components used in the preparation of lanthanide-based diene polymerizationcatalysts. Each of the R2AlCl reagents can replace a carboxylate ligand with chloride inreactions with [(C5Me5)2Sm(O2CC6H5)]2, but instead of forming a simple chloride complexlike [(C5Me5)2SmCl]3, bimetallic lanthanide aluminum dichloro complexes (C5Me5)2Sm(
-Cl)2AlR2 are generated by ligand redistribution. These bis(chloride)-bridged complexesare also readily formed from the divalent precursor (C5Me5)2Sm(THF)2 and R2AlCl. However,the analogous reaction between (C5Me5)2Sm(THF)2 and Et3Al gives (C5Me5)2Sm(THF)(-
2-Et)AlEt3, which contains the first Ln(III)-(2-Et) linkage, a coordination mode thatdifferentiates Et from Me. To determine if mixed mono-chloride/alkyl-bridged (C5Me5)2Ln(-Cl)(-R)AlR2 complexes can be isolated, (C5Me5)2Y(-Cl)YCl(C5Me5)2 was reacted withR3Al. These reactions form [(C5Me5)2Y(-Cl)(-R)AlR2]x complexes, but again there is adifferentiation on the basis of R: the Me complex is a dimer and the others are monomers.(C5Me5)2Y(-Cl)2AlR2 complexes were similarly prepared for comparison with the mixed ligandspecies and for additional Me, Et, and iBu comparisons.
-Cl)2AlR2 are generated by ligand redistribution. These bis(chloride)-bridged complexesare also readily formed from the divalent precursor (C5Me5)2Sm(THF)2 and R2AlCl. However,the analogous reaction between (C5Me5)2Sm(THF)2 and Et3Al gives (C5Me5)2Sm(THF)(-2-Et)AlEt3, which contains the first Ln(III)-(2-Et) linkage, a coordination mode thatdifferentiates Et from Me. To determine if mixed mono-chloride/alkyl-bridged (C5Me5)2Ln(-Cl)(-R)AlR2 complexes can be isolated, (C5Me5)2Y(-Cl)YCl(C5Me5)2 was reacted withR3Al. These reactions form [(C5Me5)2Y(-Cl)(-R)AlR2]x complexes, but again there is adifferentiation on the basis of R: the Me complex is a dimer and the others are monomers.(C5Me5)2Y(-Cl)2AlR2 complexes were similarly prepared for comparison with the mixed ligandspecies and for additional Me, Et, and iBu comparisons.