Organomagnesium compounds coordination geometry

As has been outlined before, the preferred coordination geometry at magnesium in organomagnesium compounds is tetrahedral, although also organomagnesium compounds are known with either lower or higher coordination numbers. 

Although the tetrahedral coordination geometry is preferred by organomagnesium compounds, many examples have been structurally characterized which show deviating coordination numbers. In most cases, this... 

The crystal packing of organomagnesium compounds has shown that intramolecular coordination is preferred over solvent coordination. These compounds have a tetrahedral geometry. The crystal structure of [MeO(CH2)4]aMg [Compound 27] indicates that the... 

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