A Kinetic Study on the Substitution for Acetonitrile at the trans-to-Oxido Sites in a Bis(mu-acetato)(mu-oxido)diruthenium(III) Dipositive Complex: Dissociative-Associative Transition of the Activation Mode for the Substitution of Pyridine Derivatives

作者：Ido Yohei; Sakaguchi Kiyoshi; Tasei Minako; Minami Suguru; Sawamoto Hiroki; Fujihara Takashi; Nagasawa Akira^*

来源：European Journal of Inorganic Chemistry, 2013, 2013(21): 3641-3650.

DOI：10.1002/ejic.201300173

• Kinetics
• Substituent effects
• Oxido bridges
• Ruthenium
• Dissociative-associative transitions

%26lt;title content-type=%26quot;main%26quot;%26gt;Abstract %26lt;br%26gt;A new diruthenium(III) complex [Ru-2(III)(-O)(-CH3CO2)(2)(bpy)(2)(CH3CN)(2)](PF6)(2) [1(PF6)(2), bpy = 2,2-bipyridine] has been synthesized, and the dynamic behaviour of CH3CN at the trans-to--oxido sites were investigated by H-1 NMR and UV/Vis spectroscopy at 0-60 degrees C under 0.101-147 MPa in CH3CN. The solvent exchange in CD3CN at 5 degrees C gave the rate constant k = 2.43x10(-3) s(-1) and the activation parameters H-double dagger = 124 kJmol(-1) and S-double dagger = +150 JK(-1)mol(-1), which point to a dissociative mechanism (I-d or D). The ligand substitution of pyridine (py) in CD3CN at 30 degrees C, yielding [Ru-2(III)(-O)(-CH3CO2)(2)(bpy)(2)(py)(2)](PF6)(2) [2a(PF6)(2)], gave a rate constant per site of k = 1.56x10(-2) M(-1)s(-1), and the activation parameters H-double dagger = 81 kJmol(-1) and S-double dagger = -13 JK(-1)mol(-1). The substitution of various pyridine derivatives (Rpy) for CH3CN in 1(PF6)(2) exhibited varying activation parameters: H-double dagger ranged from 66 to 92 kJmol(-1), S-double dagger ranged from -51 to +22 JK(-1)mol(-1), and V-double dagger (for Rpy with R = H, 3-Ac, 4-NH2, 4-CN, 3-CN) ranged from +1.3 to +3.2 cm(3)mol(-1). These results suggest an interchange (I) mechanism for the substitution of Rpy, for which its strong electron-donating ability is responsible. A compensation effect is seen between H-double dagger and S-double dagger, and both have linear relationships with the Hammett parameters. The substituent R electronically influences the strength of the interaction of Rpy with Ru center in the transition state to shift the activation mode to a dissociative (I-d) or an associative (I-a) interchange.

• 出版日期2013-7