Synthesis and crystal structure of the new heteroleptic magnesium bis(amide) [{Mg[μ-N(H)Ph][N(SiMe3)2]•THF}2], and density functional MO calculations on model systems

Reaction of Mg[N(SiMe3)(2)](2) with one molar equivalent of the primary amine PhNH2 in THF solution gave the transaminated THF-solvated heteroleptic bis(amide) [{Mg[mu -N(H)Ph][N(SiMe3)(2)]. THF}(2)]. In the crystalline state the new amide is dimeric with a central, planar azamagnesacyclic (NMg)(2) ring. The resonance stabilised anilido units prefer to bridge to the magnesium centres whereas the bulkier secondary hexamethyldisilazanzide groups occupy terminal sites. Terminal solvation by THF completes the distorted tetrahedral environment about magnesium. Comparisons of this structure with other crystallographically characterised heteroleptic magnesium bis(amides) are made. The interesting, almost square geometry of this (NMg)(2) ring has also prompted a density functional MO study on magnesium systems and related molecules of Groups 1, 2 and 13, the results of which are also reported.