Azide-rich complexes of cobalt(III) with the rare 5-phenyl-2,2 %26apos;-bipyridine ligand

作者：Safin Damir A; Robeyns Koen; Vande Velde Christophe M L; Thijs Mike; Mitoraj Mariusz P; Sagan Filip; Filinchuk Yaroslav

来源：Inorganica Chimica Acta, 2017, 459: 63-72.

DOI：10.1016/j.ica.2017.01.020

• Cobalt
• Azide
• X-ray crystallography
• Thermal analysis
• DFT

Reaction of one or two equivalents of 5-phenyl-2,2 '-bipyridine (L) with a mixture of one equivalent of CoCl2 and two equivalents of NaN3 leads to mononuclear heteroleptic cobalt(III) complexes [CoL2(N-3)(2)] (N-3)(0.55)Cl-0.45.EtOH (1) and [CoL2(N-3)(2)]N-3.2.5EtOH (2), respectively. Both structures reveal that cobalt (III) atom is linked to the six nitrogen atoms of two L and two Ni anions. Both structures are stabilized by intermolecular C-H...N and pi...pi stacking interactions. TG and DSC analyses reveal 1 being stable up to 63 degrees C and decomposing in three steps, 2 on the other hand decomposes at 84 degrees C in two steps. Both decomposition pathways start with an endothermic loss of the lattice ethanol molecules. The second step in 1 (177 degrees C) and 2 (196 degrees C) is related to the "jet" effect, seen as an abrupt weight loss due to a drastic energy release upon heating. In 2 this is the result of a release of N-2 gas from the azides and decomposition of the ligands L followed by the full reduction of cobalt(III) to cobalt(0). In 1 there is a loss of one azide accompanied by the reduction of cobalt(III) to cobalt(II). The final decomposition step of 1 at 215 degrees C is attributed to the exothermic decomposition of L and remaining azide with the formation of a mixture of CoCl2 and Co2N. DFT calculations are performed in order to shed additional light on possible spin states of cobalt complexes as well as to rationalize the stability of the synthesized materials.

• 出版日期2017-4-1