Bimetallic Complexes of Metallacyclopentynes: cis versus trans and Planarity versus Nonplanarity
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- 作者：Marc A. Bach ; Pattiyil Parameswaran ; Eluvathingal D. Jemmis ; Uwe Rosenthal
- 刊名：Organometallics
- 出版年：2007
- 出版时间：April 23, 2007
- 年：2007
- 卷：26
- 期：9
- 页码：2149 - 2156
- 全文大小：334K
- 年卷期：v.26,no.9(April 23, 2007)
- ISSN：1520-6041
文摘
Density functional theory calculations show that the Cp2M in cis-dimetallabicycles of metallacyclopentynes, Cp2M[
-(
4:2-H2C4H2)]M'L2 (M = Ti, Zr and M' = Ti, Zr), deviates from the C4 plane.Both the metal fragments deviate from the C4 plane in the nickel complexes of metallacyclopentynes(3Ti-Ni and 3Zr-Ni). The nonplanarity of Ni(PH3)2 from the C4 plane reduces the antibonding interactionbetween nickel orbitals and the 
-MO at the C2-C3 bond, whereas that of the Cp2M acts mainly toreduce the antibonding interaction between C1 and C2. The energetics of the isodesmic equations showthat the nickel complexes 3Ti-Ni and 3Zr-Ni are more stable than the homodimetallabicycles, 3Zr-Zrand 3Ti-Ti. The electron deficiency on the cis-homodimetallabicycles due to the vacant d-orbital on2-M' can be decreased by accepting electrons from a Lewis base or by flipping into trans geometry.This is reflected in the experimental realization of cis-Cp2Zr[-(4:2-H2C4H2)]ZrCp2(PMe3) and the transgeometry for Cp2Ti[-(3:3-H2C4H2)]TiCp2 and Cp2Zr[-(3:3-H2C4H2)]ZrCp2.
-(4:2-H2C4H2)]M'L2 (M = Ti, Zr and M' = Ti, Zr), deviates from the C4 plane.Both the metal fragments deviate from the C4 plane in the nickel complexes of metallacyclopentynes(3Ti-Ni and 3Zr-Ni). The nonplanarity of Ni(PH3)2 from the C4 plane reduces the antibonding interactionbetween nickel orbitals and the -MO at the C2-C3 bond, whereas that of the Cp2M acts mainly toreduce the antibonding interaction between C1 and C2. The energetics of the isodesmic equations showthat the nickel complexes 3Ti-Ni and 3Zr-Ni are more stable than the homodimetallabicycles, 3Zr-Zrand 3Ti-Ti. The electron deficiency on the cis-homodimetallabicycles due to the vacant d-orbital on2-M' can be decreased by accepting electrons from a Lewis base or by flipping into trans geometry.This is reflected in the experimental realization of cis-Cp2Zr[-(4:2-H2C4H2)]ZrCp2(PMe3) and the transgeometry for Cp2Ti[-(3:3-H2C4H2)]TiCp2 and Cp2Zr[-(3:3-H2C4H2)]ZrCp2.