Copper(II) acetate is frequently used as a catalyst for bond-forming reactions in organic synthesis. Unlike aqueous solutions, in which complete heterolysis to CuOAc+(aq) and AcO–(aq) prevails at low concentrations, it is clear that copper(II) acetate shows a large degree of aggregation in typical organic solvents. Here, the speciation behavior of Cu(OAc)2 in organic solvents is probed by electrospray ionization mass spectrometry (ESI-MS), which reveals an extensive clustering of copper acetate species to form ions of the general composition [Cun(X)2n–1]+ and [Cun(X)2n+1]– (X = OAc and OCH3), along with (solvated) monomeric species such as [Cu(OAc)(CH3OH)n]+. The ESI-MS measurements are complemented by solution-phase studies of Cu(OAc)2 by electron paramagnetic resonance spectroscopy, which support an extensive aggregation of Cu(OAc)2 in organic solvents. Collisional experiments reveal that either simple degradation or redox processes can be observed, depending on the coordinative saturation of the copper clusters. The formation of the copper clusters can be efficiently suppressed by contamination of the organic solvents by a small amount of water.

中文翻译：

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乙酸铜 (II) 在简单有机溶剂中的形态行为 - 揭示微量水的影响

醋酸铜 (II) 经常用作有机合成中成键反应的催化剂。与在低浓度下完全异解为 CuOAc+(aq) 和 AcO–(aq) 的水溶液不同，乙酸铜 (II) 在典型的有机溶剂中表现出很大程度的聚集。在这里，Cu(OAc)2 在有机溶剂中的形态行为是通过电喷雾电离质谱 (ESI-MS) 探测的，它揭示了醋酸铜物质的广泛聚集，形成了一般组成的离子 [Cun(X)2n– 1]+ 和 [Cun(X)2n+1]–（X = OAc 和 OCH3），以及（溶剂化的）单体物质，如 [Cu(OAc)(CH3OH)n]+。ESI-MS 测量通过电子顺磁共振光谱对 Cu(OAc)2 的溶液相研究进行补充，支持 Cu(OAc)2 在有机溶剂中的广泛聚集。碰撞实验表明，根据铜簇的配位饱和度，可以观察到简单的降解或氧化还原过程。通过少量的水污染有机溶剂，可以有效地抑制铜簇的形成。