Literature and the Logos

Steric Blocking of Methyl Bridging: The Syntheses and X-ray Crystal Structures of a Three-Coordinate Methyl Magnesium Complex and Its THF Adduct

“…Neither 1 or 2 shows any reactivity toward ethene up to 80 °C and 30 bar pressure in toluene solution. Given the reported ability of dialkylmagnesium species (e.g., MgEt 2 ) in hydrocarbon solution to insert ethene into the Mg−C σ-bond to provide liquid hydrocarbons ranging from C 10 up, we ascribe this failure to the steric congestion around the Mg−CH 3 unit in these complexes. Although this difference in reactivity could also be ascribed to electronic changes brought about by the nitrogen ligation of the Mg ion.…”

“…The formation of a stable six-membered chelate, coupled with the potential for variation of the steric and electronic properties of the nitrogen substituents, and the more subtle effects that may be achieved by substitution of the ligand carbon backbone provide for a useful range of steric and electronic properties essential for the fine-tuning of structure and reactivity. Sometime ago we realized that the known ability of Grignard reagents to effect carbomagnesation of certain alkenes and the limited work demonstrating the ability of some magnesium dialkyls to oligomerize ethene suggested the possibility that organomagnesium species, supported by a suitable ligand system, could be induced to exhibit alkene polymerization activity. At the time such activity was restricted to complexes of the early transition and lanthanide metals.…”