A Range of Nitrato Coordination Modes in Ni^IIComplexes with the Versatile Ligand 1,8‐Bis(2‐pyridyl)‐3,6‐dithiaoctane: Structural, Spectroscopic, Electrochemical, and Theoretical Studies

Abstract

We have synthesized a series of NiII‐pdto complexes – [Ni(pdto)(NO3)]NO3·H2O (C1), [Ni(pdto)(H2O)2](NO3)2 (C2), and [Ni(pdto)(NO3)(H2O)]NO3 (C3), with pdto = 1,8‐bis(2‐pyridyl)‐3,6‐dithiaoctane – with different spectroscopic responses associated with the coordination modes of the nitrato moiety. Through UV/Vis spectroscopy and electrochemical experiments it was established that in acetonitrile solution the compounds C1, C2, and C3 are each transformed into the same chemical species [Ni(pdto)NO3]+. Cyclic voltammetry experiments gave evidence of two consecutive one‐electron transfers associated with NiII‐(pdto) + 1 e– → NiI‐(pdto) and NiI‐(pdto) + 1 e– → Ni0 + pdto processes, which are in agreement with the high flexibility of the pdto ligand with regard to accommodating the preferred geometry of the central atom. The complexation reaction between pdto and the starting salt Ni(NO)3·6 H2O in acetonitrile was also studied by UV/Vis spectroscopy and cyclic voltammetry. A linear relationship between the experimentally determined value of 10 Dq and the Δ(EHOMO–LUMO) energy values obtained by computational methods was found.