Effect of High Hydrostatic Pressure on Aqueous Organometallic Systems

Effect of High Hydrostatic Pressure on Aqueous Organometallic Systems 

Since the late 1960s pressure has become a common and important variable in the study of chemical kinetics and equilibrium [11-13, 66]. High-pressure techniques have been developed for the majority of physicochemical methods (NMR, IR, and UV-visible spectroscopy, electrochemistry, etc.), generally up to 200 MPa (= 2000bars) pressure [14, 15]. Applications for organometallic aqueous systems are shown here. 

The pressure dependence of a rate constant, k, is given by Eq. (1) where AVs is the volume difference between the volume of the transition state and the volume of the reactants. Generally the pressure dependence of Ink is linear, and the compressibility of the transition state can be neglected. Symmetric reactions like solvent exchange are especially suited to the study of the effect of pressure on the re- 

M = Os (the organometallic aquo ions were enriched previously in H2170). 

A high-pressure stopped-flow technique [22] was applied to study the complex formation reactions between [Pt(L)(H20]+ and Nj or tmtu, where L = C6H3(CH2NMe2)2-2,6 [23] or N,N-dimethylbenzylamine and pyridine-3-sulfonic acid [24], tmtu = N,N,N, N -tetramethylthiourea. The large negative activation volumes found for the forward and reverse reactions (AV values are between —10.1 and —12.4 cm3moN1) are evidence for the operation of an associative activation mode for the substitution. 

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