Iron(ii) and cobalt(ii) complexes based on anionic phenanthroline-imidazolate ligands: reversible single-crystal-to-single-crystal transformations

A series of low-spin Fe-II and Co-II complexes based on phenanthroline-imidazolate (PIMP) ligands are reported. The Fe-II complex (H9O4)[Fe(PIMP)(3)](C4H10O)(2)(H2O) (1a) shows reversible crystalline phase transformations to afford two new phases (H9O4)[Fe(PIMP)(3)](H2O) (1b) and (H9O4)[Fe(PIMP)(3)](C8H18O)(C4H10O)(H2O) (1c) by release of diethyl ether and absorption of diethyl/dibutyl ether, respectively. This reversible uptake/release of solvent molecules is a clear example of single-crystal-to-single-crystal transformation involving a discrete metal complex. On the other hand, the corresponding Co-II complex (H9O4)[Co(PIMP)(3)](C4H10O)(2)(H2O)(2) (2) does not exhibit similar phase transformations. In the neutral complexes [Fe(H-TfPIMP)(TfPIMP)(2)](EtOH)(4)(H2O)(7) (3) and [Co(H-TfPIMP)(TfPIMP)(2)](EtOH)(2)(H2O)(2) (4), which crystallized in the polar space group Pna2(1) and in the centrosymmetric space group P2(1)/n, respectively, one of the imidazole ligands was not deprotonated.