Bis(quinoxaline-dithiolato)nickel(III) Complexes [Bu < inf > 4 < /inf > N][Ni < sup > III < /sup > (6,7-qdt) < inf > 2 < /inf > ] and [Ph < inf > 4 < /inf > P][Ni < sup > III < /sup > (Ph < inf > 2 < /inf > 6,7-qdt) < inf > 2 < /inf > ]·CHCl < inf > 3 < /inf > (6,7-qdt = Quinoxaline-6,7-dithiolate; Ph < inf > 2 < /inf > 6,7-qdt = Diphenylquinoxaline-6,7-dithiolate): Synthesis, Spectroscopy, Electrochemistry, DFT Calculations, Crystal Structures and Hirshfeld Surface Analysis

Abstract

Two bis(quinoxaline-dithiolato)nickel(III) complexes [Bu4N][NiIII(6,7-qdt)2] (1; 6,7-qdt = quinoxaline-6,7-dithiolate) and [Ph4P][NiIII(Ph26,7-qdt)2]·CHCl3 (2; Ph26,7-qdt = diphenylquinoxaline-6,7-dithiolate) have been synthesized from their NiII analogues by iodine oxidation. Compounds 1 and 2 have been characterized by routine spectral analysis and single-crystal X-ray structure determination. Nickel(III) complexes 1 and 2 exhibit redshifted absorption bands compared with their NiII analogues; the electronic absorption spectral studies have been corroborated by DFT calculations. Electrochemical studies on 1 and 2 are consistent with those of their NiII analogues. Electron spin resonance (ESR) studies confirm that nickel is present in both 1 and 2 in its +3 oxidation state. This is also consistent with the fact that only one cation (Bu4N+ for 1 and Ph4P+ for 2) is present in the respective crystal structures. The crystal structures of both compounds are characterized by C-H⋯S and C-H⋯N hydrogen-bonding interactions. Hirshfeld surface analyses have been studied to gain deep insight into the hydrogen-bonding interactions around/among the coordination complex anions. Two bis(dithiolato)NiIII complexes have been synthesized from their respective NiII analogues by iodine oxidation. They are characterized by routine spectroscopic analyses and single-crystal X-ray crystallography. Electronic spectroscopy and the supramolecular chemistry are corroborated with DFT calculations and Hirshfeld surface analyses, respectively.