Charge Density Analysis of the (C−C)→Ti Agostic Interactions in a Titanacyclobutane Complex
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- 作者：Stephan Scheins ; Marc Messerschmidt ; Milan Gembicky ; Mateusz Pitak ; Anatoliy Volkov ; Philip Coppens ; Benjamin G. Harvey ; Gregory C. Turpin ; Atta M. Arif ; Richard D. Ernst
- 刊名：Journal of the American Chemical Society
- 出版年：2009
- 出版时间：May 6, 2009
- 年：2009
- 卷：131
- 期：17
- 页码：6154-6160
- 全文大小：339K
- 年卷期：v.131,no.17(May 6, 2009)
- ISSN：1520-5126
文摘
The experimental electron density study of Ti(C5H4Me)2[(CH2)2CMe2] provides direct evidence for the presence of (C−C)→Ti agostic interactions. In accord with the model of Scherer and McGrady, the Cα−Cβ bond densities no longer show cylindrical symmetry in the vicinity of the Ti atom and differ markedly from those of the other C−C bonds. At the points along the Cα−Cβ bond where the deviation is maximal the electron density is elongated toward the metal center. The distortion is supported by parallel theoretical calculations. A calculation on an Mo complex in which the agostic interaction is absent supports the Scherer and McGrady criterion for agostic interactions. Despite the formal d0 electron configuration for this Ti(IV) species, a significant nonzero population is observed for the d orbitals, the d orbital population is largest for the dxy orbital, the lobes of which point toward the two Cα atoms. Of the three different basis sets for the Ti atom used in theoretical calculations with the B3LYP functional, only the 6-311++G** set for Ti agrees well with the experimental charge density distribution in the Ti−(Cα−Cβ)2 plane.