Evaluation of Enthalpy Change and Activation Enthalpy of the Reaction of Metal Complexes in Solution

在正丙胺(pa，36.1×2.3kJmol^-1)、正己胺(34.9×1.0kJmol^-1)、2-甲氧基乙胺(MEEA，44.8*3.1kJmol^-1)和苯甲胺(50.1*3.6kJmol^-1&gt；-1)等伯烷基胺中，得到了钴(II)离子在八面体和四面体钴(II)离子之间唯一平衡的热差。通过对由吸收光谱数据得到的八面体和四面体配位体的配位场稳定化能的补偿，由DeltaH^0的值估算了六配位和四配位Co(II)配合物在伯烷基胺溶剂中球对称场中的能级之差。已经证实，DELTAH值是决定DELTAH0值的决定性因素，并且在很大程度上取决于电子斥力。将这一概念应用于溶剂交换反应基态与解离过渡态能级差的讨论。实验比较了Pa和MEEA中Co(II)离子的溶剂交换反应的活化热(DELTAH^*)，发现Pa中Co(II)离子的速率常数出乎意料地大是由于Pa中Co(II)离子的小。DELTAH^*值，这是由基态中的强电子斥力引起的。

The enthalpy differences (DELTAH^0) of the unique equilibrium between octahedral and tetrahedral cobalt(II) ion have been obtained in some primary alkylamine such as n-propylamine (pa, 36.1*2.3 kJ mol^<-1>), n-hexylamine (34.9*1.0 kJ mol^<-1>), 2-methoxyethylamine (meea, 44.8*3.1 kJ mol^<-1>), and benzylamine (50.1*3.6 kJ mol^<-1>). The differences between energy levels of the six- and four-coordinate Co(II) complexes in the spherically symmetric field (DELTAE_<spher>) in the primary alkylamine solvents have been estimated from the values of deltaH^0 by offsetting the ligand field stabilization energies for the octahedral and tetrahedral geometries obtained from the absorption spectral data. It has been confirmed that the values of DELTAE_<spher> is the decisive factor to determine the value of DELTAH^0 and is largely dependent on the electronic repulsion. This concept has been applied to the discussion about difference in energy levels between ground state and dissociative transition state of the solvent exchange reaction. The comparison between activation enthalpy (DELTAH^*) of the solvent exchange reaction of cobalt(II) ion in pa and meea has experimentally revealed that unexpectedly large rate constants of cobalt(II) ion in pa is attributed to small. DELTAH^* value which results from the strong electronic repulsion in the ground state.