Syntheses and structural diversity of salicylideneaniline derivatives with cobaltadithiolene backbone

Salicylideneaniline (SA) or benzylideneaniline (BA) derivatives with [CpCo(dithiolene)] backbone, which are formulated as [CpCo(S2C2(H)(R))] (R = 5-chlorosalicylideneaniline (2a), salicylideneaniline (2b), benzylideneaniline (2c) and 3,5-di-t-butylsalicylideneaniline (2d)), were prepared from the aniline precursor [CpCo(S2C2(H)(C6H4-NH2))] (1) and the corresponding aldehydes. 1 and 2a–2d were identified with spectral data and electrochemical redox potentials. 1 and 2a–2c were structurally determined by X-ray diffraction studies. 1 and 2a showed dithiolene-H⋯X hydrogen bondings (X = N (1), O (2a)), because the dithiolene proton is usually acidic (ca. 9 ppm by 1H NMR). In 2a–2c, the dihedral angles between two benzene rings (θ1) in the SA (or BA) moieties were depending on the substituents on these benzene rings. 2a has small θ1 angle (7.321°) and the result indicates a short intramolecular OH···N hydrogen bonding distance (1.743 Å). In the crystal of 2b (or 2c), there are two (or four) crystallographically independent molecules, and their θ1 angles are different by the flexible SA (or BA) unit. The crystal 2b contains a non-planar molecule (θ1 = 37.043°) and a relatively planar molecule (θ1 = 22.822°) as well.