# Bimetallic Complexes of Metallacyclopentynes: cis versus trans and Planarity versus Nonplanarity

Bach, Marc A and Parameswaran, Pattiyil and Jemmis, Eluvathingal D and Rosenthal, Uwe (2007) Bimetallic Complexes of Metallacyclopentynes: cis versus trans and Planarity versus Nonplanarity. In: Organometallics, 26 (9). pp. 2149-2156.

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## Abstract

Density functional theory calculations show that the $Cp_2M$ in cis-dimetallabicycles of metallacyclopentynes, $Cp_2M[\mu-(\eta^4:\eta^2-H_2C_4H_2)]M'L_2 (M = Ti, Zr$ 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 $Ni(PH_3)_2$ from the C4 plane reduces the antibonding interaction between nickel orbitals and the $\pi-MO$ at the C2-C3 bond, whereas that of the $Cp_2M$ acts mainly to reduce the antibonding interaction between C1 and C2. The energetics of the isodesmic equations show that the nickel complexes 3Ti-Ni and 3Zr-Ni are more stable than the homodimetallabicycles, 3Zr-Zr and 3Ti-Ti. The electron deficiency on the cis-homodimetallabicycles due to the vacant d-orbital on $\eta^2-M'$ 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-$Cp_2Zr[\mu-(\eta^4:\eta^2-H_2C_4H_2)]ZrCp_2(PMe_3)$ and the trans geometry for $Cp_2Ti[\mu-(\eta^3:\eta^3-H_2C_4H_2)]TiCp_2$ and $Cp_2Zr[\mu-(\eta^3:\eta^3-H_2C_4H_2)]ZrCp_2$.

Item Type: Journal Article Copyright of this article belongs to American Chemical Society. Division of Chemical Sciences > Inorganic & Physical Chemistry 30 Jul 2007 19 Sep 2010 04:38 http://eprints.iisc.ernet.in/id/eprint/11625