AN UNEXPECTED STRUCTURAL PRINCIPLE FOR CRYSTALLINE MGBR2-CENTER-DOT-OET(2) - CHAINS OF TRIGONAL BIPYRAMIDS

MgBr2 . OEt(2) (1), which is commercially available and has been exami ned by different methods in the past, was obtained in crystalline form as a by-product of the reaction of amine-stabilised AlCl solution wit h mesitylene magnesium bromide. The following unexpected structure was obtained by X-ray techniques: five-coordinate magnesium centres form trigonal bipyramids, which are connected by two common bromine atoms i nto chains. Structural details and especially the relationship with so lid MgBr,, MgBr2 .(OEt(2))(2) and MgI2 .(OEt(2))(2) (2) are discussed in order to illuminate the unusual bonding in 1.