The complexation of nickel(II) with acetylacetonate bis(thiosemicarbazone) N₂S₂ ligands with varying substituents has revealed that two isomers can exist independently in solution. These isomers differ according to the formation of either a 5,6,5-membered (symmetric) or a 4,7,5-membered (asymmetric) chelate ring arrangement. These two isomers have distinctly different properties. The symmetric complex (sym-[Ni(acacR)]) is unstable in the presence of air and slowly converts to the oxidised analogue sym-[Ni(acacRO)] with a carbonyl group installed at the apical C-atom. The mechanism of this O-atom transfer reaction is still unclear but kinetic and spectroelectrochemical experiments in addition to Density Functional Theory calculations have identified a single electron oxidised Ni^II–ligand radical complex as a key intermediate. By contrast the asymmetric complex, asym-[Ni(acacR)] is inert to ligand oxidation.

中文翻译：

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乙酰丙酮 镍（ii）双（硫代半碳carb酮）配合物的异构性和反应性†

镍（II）与具有不同取代基的乙酰丙酮双（硫代半脲）N ₂ S ₂配体的络合表明，溶液中可以独立存在两种异构体。这些异构体根据5,6,5-元（对称）或4,7,5-元（不对称）螯合环排列的形成而不同。这两种异构体具有明显不同的性质。对称复合物（符号- [镍（acacR）]）是在空气中和慢慢地转换的存在下被氧化的类似物不稳定符号-[Ni（acacRO）]，在顶端C原子处安装有羰基。这种O原子转移反应的机理尚不清楚，但除密度泛函理论计算外，动力学和光谱电化学实验还确定了单电子氧化的Ni ^II-配体自由基络合物为关键中间体。相比之下，不对称络合物，ASYM - [镍（acacR）]是惰性的配位体的氧化。