P. N. Riley, Jennifer R. Parker, P. Fanwick
Aug 1, 1999
Citations
0
Influential Citations
32
Citations
Journal
Organometallics
Abstract
The reaction of [Cp*TaCl4] with the potassium salt of carbazole (cbK, >3 equiv) in hydrocarbon solvents leads to the species [(C5Me4CH2)Ta(cb)2Cl] (1), in which one of the ring methyl C−H bonds of the Cp* ligand has been cleaved along with free cbH. Spectroscopic and structural studies of 1 show a lack of a plane of symmetry through the molecule with nonequivalent cb ligands. A minor component of the reaction mixture is believed to be the substitutional isomer 2, in which both carbazole ligands are equivalent. Alkylation of 1 with LiCH2SiMe3 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 η1:η5-CH2C5Me4 (σ:η5-CH2C5Me4) description for the metalated ligands, with significant slippage toward an η1:η3-CH2C5Me4 resonance form. To compare the extent of π-bonding between cb and dialkylamido ligands, the complex [(cb)2Ta(NMe2)3] (9) was synthesized and structurally characterized. The molecular structure of ...