Synthesis and structural characterisation of the cyclosiloxymagesium compound [(py)2Li]2-µ-Mg[{Ph2SiO}2O][{Ph2SiO}3O] having both six- and eight-membered magnesiasiloxane rings

Abstract

The dilithium salt, [(Ph₂SiOLi·THF)₂O], reacts with MgCl₂·2THF to give, on addition of pyridine, the unexpected lithium bridged spirocyclic magnesiasiloxane compound [(py)₂Li]₂-µ-Mg[{Ph₂SiO}₂O][{Ph₂SiO}₃O] which is the first example of a molecular magnesium siloxide compound to be characterised and also the first example of a spirocyclic metallasiloxane having rings with different degrees of oligomerisation.