Synthesis and characterisation of dinuclear and mononuclear Cobalt (II) benzoate complexes

Aqua-bridged binuclear cobalt (II) benzoate complexes having pyridine as auxiliary ligands are synthesised through solid state reactions and characterised. The binuclear core in these complexes comprise of two bridging benzoates and an aqua bridge. Each of the cobalt (II) centre is further co-ordinated to one benzoate and two pyridine ligands. The aqua-bridged cobalt (II) benzoate complex [Co2(μ-H2O)(μ-OBz)2(OBz)2(Py)4] ·  (C6H6)(BzOH) (1a) is inclusion compounds with benzoic acid and benzene (where OBz  =  benzoate, py  =  pyridine). Analogous complex [Co2(μ-H2O)(μ-OBz)2(OBz)2(Py)4] · 1.5(C6H6) without benzoic acid included is also prepared by an alternative method and structurally characterised. Analogous aqua-bridged complex derived from p-chlorobenzoic acid in unsolvated form is characterised. The Co–O–Co separation in these complexes is in the range of 3.55–3.64 Å with angles Co–O–Co varying from 111.8° to 116.4°. While similar reaction in solution leads to the formation of mononuclear complex having composition [Co(OBz)2(Py)2(H2O)]. The unsubstituted benzoate complex 1a can be easily oxidised to form a tetrameric cobalt (III) complex having benzoate and oxo-bridged structure with a Co4O4 core.

Graphical abstractAqua-bridged cobalt (II) benzoate complexes are prepared through solid state synthetic route. However, synthetic route through solution resulted in mononuclear benzoate complex.Figure optionsDownload full-size imageDownload as PowerPoint slide