Chapter 3: Bonds in Organometallic Complexes
Published:09 Jul 2021
Hiroshi Nakazawa, 2021. "Bonds in Organometallic Complexes", Organometallic Chemistry, Hiroshi Nakazawa, Julian Koe
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Since a transition metal methyl complex corresponds to a compound in which one hydrogen atom of methane is replaced by a transition metal (M), the M–C bond is considered to be a covalent bond or σ-bond. To understand the properties and reactivity of organometallic complexes, it is important to understand the character of M–C σ-bonds in transition metal alkyl complexes.
How is the σ-bond between a transition metal and carbon polarized? When considering a C–Cl bond, for example, since Cl is more electronegative than C, it is expected to be polarized Cδ +–Clδ −. M–C bonds may be considered in a similar way. A table of Allred–Rochow electronegativities is given in the Appendix. The electronegativity of carbon is given as 2.5. For transition metals, the electronegativity values are between 1.1 and 1.8, showing that all transition metals have lower electronegativity than carbon. Thus in any complex LnM–CR3, it is almost certain that the polarization of the M–C bond is Mδ +–Cδ −, regardless of the identity of M, the kind of ligand L and the substituent R.