Low-dimensional compounds containing cyanido groups. Part XXX. Recrystallization of Co(II) complexes with pseudohalogenide ligands leading to CO2 uptake and formation of dicyanoguanidine anion in newly created Co(III) complexes

Two new complexes, [CoII(bpy)2(dca)2] (1) and [CoII(bpy)2(tcm)2] (2) (bpy = 2,2-bipyridine, dca = dicyanamide and tcm = tricyanomethanide) were prepared as powders. During their recrystallization on air, two other new complexes, [CoIII(bpy)2CO3]dcg (dcg = N,N′-dicyanoguanidine, (H2N)C(NCN)2) (3) and [CoIII(bpy)2CO3]tcm·2H2O (4), have been prepared. Composition of both complexes was supported by the results of thermal analyses. The presence of Co(III) atom in 3 and 4 was confirmed by UV–Vis spectra, while the presence of dcg and tcm as free anions was proved by IR spectra of these complexes. Moreover, quantum chemical calculations confirmed that dcg in 3 is present in its anionic form. Single crystal X-ray structure determination of 3 and 4 revealed the presence of [CoIII(bpy)2CO3]+ complex cations with dcg, its structure has not been published yet, and tcm counter anions, respectively. In both structures, a supramolecular networks built up from strong N–H⋯N, O–H⋯N, as well as weak C–H⋯N, C–H⋯O hydrogen bonds and aromatic π–π stacking besides electrostatic forces of attraction help to consolidate the packing.

Graphical abstract[CoII(bpy)2(dca)2] (1) and [CoII(bpy)2(tcm)2] (2) complexes (bpy = 2,2-bipyridine, dca = dicyanamide and tcm = tricyanomethanide) were prepared as powders. During their recrystallization on air, CO2 uptake was observed resulting in a formation of two new carbonato complexes, [CoIII(bpy)2CO3]dcg (dcg = N,N′-dicyanoguanidine) (3) and [CoIII(bpy)2CO3]tcm·2H2O (4).Figure optionsDownload full-size imageDownload as PowerPoint slide