Formation of Tantalum "Tuck-in" Complexes by Activation of Methyl C-H Bonds in Pentamethylcyclopentadiene Groups by Carbazole Ligation
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- 作者：Patrick N. Riley ; Jennifer R. Parker ; Phillip E. Fanwick ; and Ian P. Rothwell
- 刊名：Organometallics
- 出版年：1999
- 出版时间：August 30, 1999
- 年：1999
- 卷：18
- 期：18
- 页码：3579 - 3583
- 全文大小：121K
- 年卷期：v.18,no.18(August 30, 1999)
- ISSN：1520-6041
文摘
The reaction of [Cp*TaCl4] with the potassium salt of carbazole (cbK, >3 equiv) inhydrocarbon solvents leads to the species [(C5Me4CH2)Ta(cb)2Cl] (1), in which one of thering methyl C-H bonds of the Cp* ligand has been cleaved along with free cbH. Spectroscopicand structural studies of 1 show a lack of a plane of symmetry through the molecule withnonequivalent cb ligands. A minor component of the reaction mixture is believed to be thesubstitutional isomer 2, in which both carbazole ligands are equivalent. Alkylation of 1 withLiCH2SiMe3 or PhCH2MgCl generates the corresponding monoalkyl derivatives [(C5Me4CH2)Ta(cb)2(R)] (7 or 8, respectively). Structural studies of 1, 7, and 8 support an 
1:5-CH2C5Me4 (
:5-CH2C5Me4) description for the metalated ligands, with significant slippagetoward an 1:3-CH2C5Me4 resonance form. To compare the extent of 
-bonding between cband dialkylamido ligands, the complex [(cb)2Ta(NMe2)3] (9) was synthesized and structurallycharacterized. The molecular structure of 9 consists of a tbp arrangement of nitrogen atomswith trans, axial cb ligands. The Ta-cb distances are 0.2 Å longer than the Ta-NMe2distances. An improved (safer) procedure for the synthesis of [Ta(NMe2)5] is presented.
1:5-CH2C5Me4 (:5-CH2C5Me4) description for the metalated ligands, with significant slippagetoward an 1:3-CH2C5Me4 resonance form. To compare the extent of -bonding between cband dialkylamido ligands, the complex [(cb)2Ta(NMe2)3] (9) was synthesized and structurallycharacterized. The molecular structure of 9 consists of a tbp arrangement of nitrogen atomswith trans, axial cb ligands. The Ta-cb distances are 0.2 Å longer than the Ta-NMe2distances. An improved (safer) procedure for the synthesis of [Ta(NMe2)5] is presented.