Stereoisomers of Mn(III) complexes of ethylenebis[(o-hydroxyphenyl)glycine]

We have prepared the Mn(III) complexes rac-NaMn(EHPG)]·3H₂O (1) and rac,meso-NaMn(EHPG)]·H₂O (2), where H₄EHPG is ethylenebis(o-hydroxyphenyl)glycine], and determined their X-ray crystal structures. Complex 1 contains N(S,S)C(R,R) configurations at the N and C stereogenic centres, whilst in the unit cell of complex 2 there are two independent molecules, 2a (meso) and 2b (rac), with N(R,R)C(S,R) and N(R,R)C(S,S) configurations, respectively. Enantiomers of each complex are also present. The Mn(III) centres have Jahn-Teller-distorted octahedral geometry. The rac isomer has two long axial MnO(carboxylate) bonds (2.162-2.202 Å) and the equatorial plane contains two short MnN bonds (2.012-2.063 Å) trans to short MnO(phenolate) bonds (1.865-1.901 Å). The meso isomer has long axial MnN (2.194 Å) and MnO(carboxylate) (2.152 Å) bonds, and shorter equatorial MnN (2.005 Å) trans to MnO(phenolate) (1.901 Å) and MnO(carboxylate) (1.988 Å) trans to O(phenolate) (1.897 Å) bonds.