Metallomacrocycles from ditopic chiral scorpionate ligands

Abstract

Rare examples of heteroditopic scorpionate ligands [m-(pz(HO)BtBu)(pz₂BtBu)C₆H₄]²⁻ ([2_m]²⁻) and [p-(pz(HO)BtBu)(pz₂BtBu)C₆H₄]²⁻ ([2_p]²⁻) are reported. As a unique feature, both ligands possess a chiral boron centre. Treatment of [2_m]²⁻ and [2_p]²⁻ with Fe^II and Co^II ions, respectively, gives the dinuclear metallomacrocycles [Fe^II₂(µ-2_m)₂] and [Co^II₂(µ-2_p)₂]. The molecular structures of the colourless complex [Fe^II₂(µ-2_m)₂] and the red–purple complex [Co^II₂(µ-2_p)₂] have been determined by X-ray crystallography. To meet the geometric requirements of macrocycle formation, the two asymmetric boron centres have opposite absolute configurations in the case of [Fe^II₂(µ-2_m)₂] and the same configuration in [Co^II₂(µ-2_p)₂].