Polymorphism of the dinuclear CoIII–Schiff base complex Co2(o-van-en)3·4CH3CN (o-van-en is a salen-type ligand)

摘要

Reactions of Co(OH)2 with the Schiff base bis­(2-hy­droxy-3-meth­oxy­benzyl­idene)ethyl­enedi­amine, denoted H2(o-van-en), under different conditions yielded the previously reported complex aqua­[bis­(3-meth­oxy-2-oxido­benzyl­idene)ethyl­enedi­amine]­cobalt(II), [Co(C18H18N2O4)(H2O)], >1, under anaerobic conditions and two polymorphs of [μ-bis­(3-meth­oxy-2-oxido­benzyl­idene)ethyl­enedi­amine]­bis­{[bis­(3-meth­oxy-2-oxido­benzyl­idene)ethyl­enedi­amine]­cobalt(III)} aceto­nitrile tetra­solvate, [Co2(C18H18N2O4)3]·4CH3CN, i.e. monoclinic >2 and triclinic >3, in the presence of air. Both novel polymorphs were chemically and spectroscopically characterized. Their crystal structures are built up of centrosymmetric dinuclear [Co2(o-van-en)3] complex mol­ecules, in which each Co^III atom is coordinated by one tetra­dentate dianionic o-van-en ligand in an uncommon bent fashion. The pseudo-­octa­hedral coordination of the Co^III atom is completed by one phenolate O and one amidic N atom of the same arm of the bridging o-van-en ligand. In addition, the asymmetric units of both polymorphs contain two aceto­nitrile solvent mol­ecules. The polymorphs differ in the packing orders of the dinuclear [Co₂(o-van-en)₃] complex mol­ecules, i.e. alternating ABABAB in >2 and AAA in >3. In addition, differences in the conformations, the positions of the aceto­nitrile solvent mol­ecules and the pattern of inter­molecular inter­actions were observed. Hirshfeld surface analysis permits a qualitative inspection of the differences in the inter­molecular space in the two polymorphs. A knowledge-based study employing Full Inter­action Maps was used to elucidate possible reasons for the polymorphism.