Metallomacrocycles from ditopic chiral scorpionate ligands

Rare examples of heteroditopic scorpionate ligands [ m-( pz( HO)BtBu)(pz(2)BtBu)C6H4](2-) ([2m](2-)) and [ p-( pz( HO) BtBu)( pz(2)BtBu)C6H4](2-) ([2p](2-)) are reported. As a unique feature, both ligands possess a chiral boron centre. Treatment of [2(m)](2-) and [2(p)](2-) with FeII and CoII ions, respectively, gives the dinuclear metallomacrocycles [Fe-2(II)(mu-2(m))(2)] and [Co-2(II)(mu-2(p))(2)]. The molecular structures of the colourless complex [Fe-2(II)(mu-2(m))(2)] and the red-purple complex [Co-2(II)(mu-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 con. gurations in the case of [Fe-2(II)(mu-2(m))(2)] and the same con. guration in [Co-2(II)(mu-2(p))(2)].