An aluminum complex of a tripodal tris-(nitroxide)-based ligand has been prepared and characterized. The complex has the ability to participate in metal−ligand cooperative catalysis, which has been exploited for the hydroboration of both aldehydes and ketones. This represents new, transition-metal-like reactivity for an earth-abundant metal.

We report the synthesis of aluminum complexes of pyridyl nitroxide (R pyNO −) ligands. The dimeric complexes {(-pyNO −)Al(CH 3) 2 } 2 (1) and {(-CH 3 pyNO −)Al(CH 3) 2 } 2 (2) were prepared through the 1:1 reaction between the pyridyl hydroxylamine ligand precursors R pyNOH and trimethylaluminum. Both compounds were characterized by 1 H and 13 C NMR spectroscopies. Xray structural analysis revealed that 1 and 2 are isostructural, with the dimer structure resulting from an Al 2 O 2 core. Reaction of pyNOH with two equivalents of trimethylaluminum yielded the aluminum complex (pyNO −)AlMe 2 AlMe 3 (3), which was also characterized by 1 H and 13 C NMR spectroscopies and single-molecule X-ray diffraction. The electronic structure of the {(-pyNO −)Al(CH 3) 2 } 2 and {(-CH 3 pyNO −)Al(CH 3) 2 } 2 complexes were interrogated using UV-Vis