Group 4 metal substituents ground-state effects

The C-M a bonds (where M = Si, Ge, Sn, Pb) in the fragment C-MR3 (R = alkyl, aryl) are powerful a donor orbitals the electrons in the C-M bond are weakly held and easily ionized, and, importantly, the C-M bonding electrons are polarized towards the carbon. As a result, the presence of group 4 metal substituents in organic compounds has long been recognized to have very profound effects on both the ground-state properties and reactivities of the compounds.10-13 The most well known of these effects is the silicon (3-effect,10 12 which is the... 

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