A Study on Structure and Spin Equilibria of Metal Complexes in Solution.

二价过渡金属离子在非质子供体溶剂中与卤素离子形成一系列单核配合物。这些金属离子通常与溶剂分子六配位，并且在与卤素离子络合时，金属离子周围的配位结构变为四配位。据认为，卤素络合物由两个平衡物种与不同数量的配位溶剂分子。平衡可能随温度而变化。因此，在本工作中，我们研究了络合热力学参数的温度依赖性和个别配合物的电子光谱，通过使用一个精确的滴定量热系统和分光光度滴定系统，在二甲基乙酰胺（DMA）中，镍（II）离子的氯络合反应的反应焓和熵值显示出显着的温度依赖性。结果表明，配合物由[NiCl（DMA）_5]^+和[NiCl（DMA）_4]^+以及[NiCl_2（DMA）_3]和[NiCl_2（DMA）_2]组成。锌（II）的卤代络合反应的焓和熵值表明，金属溶剂化物离子中配位溶剂分子的数目小于6个，这意味着[Zn（DMA）_6]^<2+>和[Zn（DMA）_4]^<2+>存在于DMA中。[Ni（dtp）_2]（dtp =二硫代磷酸盐（C_2H_5）O_2PS_2）与各种氮给体配体的加合反应，由于其电子态由低自旋向高自旋转变，因此用电子能谱和电子能谱研究了它们的加合反应。

Bivalent transition metal ions form a series of mononuclear complexes with halide ions in aprotic donor solvents. These metal ions are usually six-coordinated with solvent molecules and the coordination structure around a metal ion changes to four-coordination upon complexation with halide ions. It is suggested that a halogeno complex consists of two equilibrium species with different numbers of coordinating solvent molecules. The equilibrium may change with temperature. Thus, in this work, we investigated temperature dependence of themodynamic parameters of complexation and electronic spectra of individual complexes by using a precise titration calorimetry system and spectrophotometric titration system developed in our laboratory.In dimethylacetamide (DMA), the reaction enthalpy and entropy values of chloro complexation of the nickel (II) ion show remarkable temperature dependence. The result is consistent with that from electronic spectra, suggesting that the monochloro complex consists of [Nicl(DMA)_5]^+ and [NiCl(DMA)_4]^+, and the dichloro complex [NiCl_2(DMA)_3] and [NiCl_2(DMA)_2]. The reaction enthalpy and entropy values of halogeno complexation of the zinc (II) ion suggested that the number of coordinating solvent molecules in the metal solvate ion is less than six, implying that [Zn(DMA)_6]^<2+> and [Zn(DMA)_4]^<2+> are present in DMA. In fact, an EXAFS spectroscopy shows the average coordination number of 4.6.The adduct formation reaction between [Ni(dtp)_2] (dtp = dithiophosphate (C_2H_5)O_2PS_2) with various nitrogen-donor ligands have been thermodynamically and spectrophotometrically studied, because its electronic state changes from low spin to high spin upon complexation.