The visible absorption spectra of CoX2 (X=Cl, Br) in 3-methylpyridine (3-Me-py) solutions have been measured in the pressure range of 1 bar—3 kbar at room temperature, and in the temperature range of ≈5–≈76 °C at 1 bar. The equilibrium, [CoX2(3-Me-py)2] (tetrahedral)+2(3-Me-py)\ightleftharpoons[CoX2(3-Me-py)4] (octahedral), is found to be followed over this pressure range. Higher pressures favor the octahedral species with the volume changes −18–−19 cm3 mol−1 at 1 bar. On the other hand, the above equilibrium holds fairly well at temperatures up to about 40 °C. Higher temperatures favor the tetrahedral species, the heats of reaction, being 56.7 kJ mol−1 (5.0–44.8 °C) and 58.6 kJ mol−1 (4.8–34.2 °C) for the chloro and bromo complexes, respectively. An intense and broad band appears around 400 nm at elevated temperatures especially for the bromo complex solution. This band may be assigned to a charge-transfer band occurring in a contact ion pair of solvent molecule 3-Me-py with X− arising from the dissociation of the tetrahedral species [CoX2(3-Me-py)2].
室温下在1 bar—3 kbar压力范围内以及在≈5温度范围内测量了CoX2(X=Cl,Br)在3-
甲基吡啶(3-Me-py)溶液中的可见吸收光谱– 约 76 °C(1 巴)。发现平衡 [CoX2(3-Me-py)2] (四面体)+2(3-Me-py)\ightleftharpoons[CoX2(3-Me-py)4] (八面体)压力范围。较高的压力有利于八面体物质,在 1 bar 下体积变化为 -18–−19 cm3 mol−1。另一方面,上述平衡在高达 40°C 左右的温度下保持得相当好。较高的温度有利于四面体物质,
氯和
溴配合物的反应热分别为 56.7 kJ mol−1 (5.0–44.8 °C) 和 58.6 kJ mol−1 (4.8–34.2 °C)。在高温下,特别是对于
溴配合物溶液,在 400 nm 附近出现强烈且宽的谱带。该带可归属于溶剂分子 3-Me-py 与 X- 的接触离子对中出现的电荷转移带,该接触离子对源自四面体物质 [CoX2(3-Me-py)2] 的解离。