A cationic aluminum methyl complex supported by an anionic tacn ligand

Reaction of (tacn)H [(tacn)H=1,4-diisopropyl-1,4,7-triazacyclononane] with AlMe3 leads to the formation of the thermally stable adduct [(tacn)H]·AlMe3 (1). The dimeric aluminum dimethyl complex [(tacn)AlMe2]2 (2) was obtained by metathesis of (tacn)Li2 with two equivalent of Me2AlCl in toluene at 80 °C. In 2 the anionic nitrogen atoms bridge the two AlMe2 units while the neutral amino atoms are free of coordination. Treatment of 2 with 2 equiv. of B(C6F5)3 in CH2Cl2 yielded a well separated ionic aluminum methyl borate complex [((tacn)AlMe)2][MeB(C6F5)3]2 (3), featuring five-coordinate aluminum centers. Molecular structures of 2 and 3 were determined by single-crystal X-ray crystallography.