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

在正丙胺（pa, 36.1*2.3 kJ mol^<-1>）、正己胺（34.9*1.0 kJ mol^<-1>）、2-甲氧基乙胺（meea, 44.8*3.1 kJ mol^<-1>）和苄胺（50.1*3.6 kJ mol^<-1>）等伯胺中，得到了钴离子在八面体和四面体间的独特平衡焓差（DELTAH^0）。通过抵消从吸收光谱数据中得到的配体八面体和四面体的场稳定能，用δ tah ^0的值估计了六坐标和四坐标Co（II）配合物在伯烷基胺溶剂中球对称场（DELTAE_<spher>）中的能级差异。已经证实，DELTAE_<球体>的值是决定DELTAE_ ^0值的决定性因素，并且在很大程度上依赖于电子斥力。这一概念已应用于溶剂交换反应基态和离解过渡态能级差的讨论。通过对pa和meea中钴（II）离子溶剂交换反应的活化焓（δ tah ^*）的比较，实验表明，pa中钴（II）离子的反应速率常数大得出乎意料，是由于其反应速率常数小。δ tah ^*值，这是由基态的强电子排斥引起的。

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.