Key Role of the Cation in the Crystallization of Chiral Tris(Anilato)Metalate Magnetic Anions

Abstract

A complete study of the role played by the usually considered “innocent” cation in the synthesis of chiral tris(anilato)metalate magnetic complexes is presented. This study is based on the rational synthesis of the family of compounds formulated as A3[MIII(C6O4X2)3] with A+ = [PPh3Et]+, [PPh3Pr]+, [PBu4]+, [NHep4]+, and [PPh4]+; MIII = CrIII, FeIII, and GaIII; and [C6O4X2]2– (X = Cl, Br, and NO2; [C6O4X2]2– = dianion of the 3,6-disubstituted derivatives of 2,5-dihydroxy-1,4-benzoquinone, H4C6O4). We show and explain the unexpected key role played by the cations in isolating chiral or achiral crystals of these [MIII(C6O4X2)3]3– anions with D3 point group symmetry. Thus, among the 18 new compounds prepared and characterized, the six obtained with the cation [PPh3Et]+, formulated as [PPh3Et]3[MIII(C6O4X2)3]3– [M/X = Cr/Cl (1), Fe/Cl (2), Ga/Cl (3), Cr/Br (4), Fe/Br (5), and Ga/Br (6)] are chiral and crystallize in the chiral and polar R3 space group. These mixtures of enantio-pure chiral crystals are obtaine...