Niobium and Tantalum Tris(methimazolyl)borate Complexes [M(NC₆H₃ⁱPr₂-2,6)Cl₂{HB(mt)₃}] (M = Nb, Ta; mt = Methimazolyl)

The first early transition metal tris(methimazolyl)borate com-plexes [M(NR)Cl₂{HB(mt)₃}] (M = Nb, Ta; R = C₆H₃ⁱPr₂-2,6; mt = methimazolyl) have been obtained from the reactions of [Nb(NR)Cl₃(DME)] or [Ta(NR)Cl₃(THF)₂] (DME = dimethyl ether; THF = tetrahydrofuran) with Na[HB(mt)₃] and structurally characterized, illustrating that the HB(mt)₃ ligand can indeed be compatible with “hard” metals in high oxidation states.