Syntheses and structural diversity of salicylideneaniline derivatives with cobaltadithiolene backbone

Abstract Salicylideneaniline (SA) or benzylideneaniline (BA) derivatives with [CpCo(dithiolene)] backbone, which are formulated as [CpCo(S 2 C 2 (H)(R))] (R = 5-chlorosalicylideneaniline ( 2a ), salicylideneaniline ( 2b ), benzylideneaniline ( 2c ) and 3,5-di- t -butylsalicylideneaniline ( 2d )), were prepared from the aniline precursor [CpCo(S 2 C 2 (H)(C 6 H 4 -NH 2 ))] ( 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 1 H NMR). In 2a–2c , the dihedral angles between two benzene rings ( θ 1 ) in the SA (or BA) moieties were depending on the substituents on these benzene rings. 2a has small θ 1 angle (7.321°) and the result indicates a short intramolecular OH···N hydrogen bonding distance (1.743 A). In the crystal of 2b (or 2c ), there are two (or four) crystallographically independent molecules, and their θ 1 angles are different by the flexible SA (or BA) unit. The crystal 2b contains a non-planar molecule ( θ 1  = 37.043°) and a relatively planar molecule ( θ 1  = 22.822°) as well.