Nature of α,β-CCC agostic bonding in metallacyclobutanes

Suresh, Cherumuttathu H. (2006) Nature of α,β-CCC agostic bonding in metallacyclobutanes Journal of Organometallic Chemistry, 691 (24-25). pp. 5366-5374. ISSN 0022328X

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Official URL: http://doi.org/10.1016/j.jorganchem.2006.07.030

Related URL: http://dx.doi.org/10.1016/j.jorganchem.2006.07.030

Abstract

The α,β-CCC agostic bonding in metallacyclobutanes is examined on the basis of structural, bonding, energetics, and electron density features. The structural features such as C α –C β , M–C α , and M–C β distances and C α C β C α and MC α C β angles of the agostic metallacyclobutanes were distinctly different from those of the corresponding non-agostic complexes. Two different orbital interactions characteristic of the agostic complex, causing the deformation of the propane-1,4-diyl unit of the metallacyclobutane were identified. The energy difference between the propane-1,4-diyl unit of metallacyclobutane in an agostic complex to that in a non-agostic complex is proposed as a good measure for the strength of α,β-CCC agostic interaction (E agostic ). E agostic values of 37.0, 36.2, 13.7, 28.6, and 23.9kcal/mol were obtained for the Grubb’s first generation Ru, Grubb’s second generation Ru, Ti, W, and Ta metallacyclobutane complexes and these values showed a linear correlation with the electron density at the ring CPs. The QTAIM features of the agostic complexes viz. the smaller ρ value at the C α –C β BCPs, larger ellipticity of the C α –C β BCPs, and diminished covalent character of C α –C β bonds as seen in their Laplacian of the electron density (∇ 2 ρ) at the BCPs, when compared with the non-agostic systems, fully supported the agostic bonding interactions. The α,β-CCC bonding is considered as the first example of a π type orbital formed between a metal atom and a carbon atom, where there is no σ bond connectivity and this type of bonding is anticipated with all transition metals provided that the metal center is highly electron deficient.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science
Keywords:Olefin metathesis, Metallacyclobutane, Agostic bonding, QTAIM theory
ID Code:127578
Deposited On:13 Oct 2022 10:56
Last Modified:13 Oct 2022 10:56

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