Anionic Multisubstituted 1,2-Azaborolyl Ligands: Syntheses, Characterization, and Coordination Chemistry

Two synthetic methods for the preparation of tri- or tetrasubstituted 1,2-azaborolyls (Ab) are described. Both tri- and tetrasubstituted Ab rings can be conveniently attained via either dilithiation-directed or Cp2ZrII-mediated cyclization followed by transmetalation in good yields. In particular, anionic 1,2,4-trimethyl-1,2-azaborolyl and 1,2,3,4-tetramethyl-1,2-azaborolyl, readily prepared through our methods, have been demonstrated as good supporting ancillary ligands in group IV metal complexes.