Impact of Positional Isomers on the Selective Isolation of <i>cis</i>-<i>trans</i> Isomers in Cobalt-Dioxolene Chemistry and Solvation Effects on the Valence Tautomerism in the Solid State

Three new mononuclear cobalt compounds─trans-[Co(3,5-dbcat)(3,5-dbsq)(4-Etpy)2]·CH3CN (1), cis-[Co(3,5-dbcat)(3,5-dbsq)(3-NH2py)2]·DMF (2), and trans-[Co(3,5-dbcat)(3,5-dbsq)(4-NH2py)2]·2DMF (3) (where 3,5-dbcat2– 3,5-dbsq• – stand for 3,5-di-tert-butyl-catecholate 3,5-di-tert-butyl-semiquinonate, respectively), derived from a redox-active o-dioxolene ligand in the presence of 4-ethylpyridine (4-Etpy), 3-aminopyridine (3-NH2py), 4-aminopyridine (4-NH2py), respectively─have been synthesized investigated with view to examine possible influence pyridine derivatives solvation on valence tautomeric (VT) process. Single-crystal X-ray diffraction data all compounds at room temperature suggest Co(III)(3,5-dbcat)(3,5-dbsq) charge distribution these complexes. Further insight into crystal structures discloses diverse non-covalent interactions offered by isomers aminopyridine 2 3, leading first example selective isolation cis trans cobalt-dioxolene chemistry induced positional ancillary ligands. Variable magnetic susceptibility between K 300 are consistent structural studies. At elevated temperatures, complex 1 exhibits VT interconversion low spin Co(III)-(3,5-dbcat)(3,5-dbsq) high Co(II)-(3,5-dbsq)(3,5-dbsq), triggered loss lattice solvent molecules, while partial is observed even heating up 430 K. The present report overall highlights impact cis-trans effects tautomerism solid state.