Solvent exchange table

J mol ). This is additional evidence in favor of rate limitation by inner diffusion. However, the same reaction in the presence of Dowex-50, which has a more open three-dimensional network, gave an activation energy of 44800 J mol , and closely similar values were obtained for the hydrolysis of ethyl acetate [29] and dimethyl seb-acate [30]. The activation energy for the hydrolysis of ethyl acetate on a macroreticular sulphonated cationic exchanger [93] is 3566 J mol . For the hydrolysis of ethyl formate in a binary system, the isocomposition activation energy (Ec) [28,92] tends to decrease as the solvent content increases, while for solutions of the same dielectric constant, the iso-dielectric activation energy (Ed) increases as the dielectric constant of the solvent increases (Table 6). 

Solvent exchange on the first-row transition metal [M(solvent)6]2+ species has been subjected to extensive study, as is exemplified by Table III, which contains data for four solvent systems which have been particularly intensively studied (46, 47, 97, 99, 103, 110-117). The solvent exchange mechanism progressively changes from Ia to Id as the number of d-electrons increases and rM decreases for H20, MeOH, and MeCN solvents, as judged from the changes in sign of AV. It is also seen that lability decreases with increase in AHi substantially, as... 

Labile species are usually main group metal ions with the exception of Cr2+ and Cu2+, whose lability can be ascribed to Jahn-Teller effects. Transition metals of classes II and III are species with small ligand field stabilization energies, whereas the inert species have high ligand field stabilization energies (LFSE). Examples include Cr3+ (3d3) and Co3+ (3d6). Jahn-Teller effects and LFSE are discussed in Section 1.6. Table 1.9 reports rate constant values for some aqueous solvent exchange reactions.8... 

The increase in ionic radius from Be2+ to Mg2+, which is accompanied by an increase in coordination number from 4 to 6, is responsible for a substantial increase in lability (Table III, (37-43)). The two activation volumes measured are positive as well as all the activation entropies. The rate laws determined for non-aqueous solvents in inert diluent are first order, showing a limiting D mechanism for all solvent exchange reactions on [MgS6]2+. 

Experimental data for solvent exchange on octahedral second- and third-row transition metal ions are limited to the Ru2+/3+, Rh3+ and Ir3+ and to water and acetonitrile solvents (Table VIII (3,125-129)). 

Replacing several solvent molecules on di- and trivalent transition metal ions by non-leaving ligands can have dramatic effects on the solvent exchange rates of the remaining solvent molecule(s) (Tables X, XI, XII and XIII (70,71,83,86-88,92,95,96,146-166) (115,119-121,167-181) (125, 128,129,167,168,181-193)). For example replacing three MeCN solvent... 

Square-planar stereochemistry is mostly confined to the d8 transition metal ions. The most investigated solvent exchange reactions are those on Pd2+ and Pt2+ metal centers and the mechanistic picture is well established (Table XIV (194-203)). The vast majority of solvent exchange reactions on square-planar complexes undergo an a-activated mechanism. This is most probably a consequence of the coordinatively unsaturated four-coordinate 16 outer-shell electron complex achieving noble gas... 

A decrease in coordination number of Ln3+ complexes results, in general, in a decrease in lability. Solvent exchange rates measured on [Ln(TMU)e]3+ are much slower than corresponding values measured on [Ln(DMF)8]3+ (56,257-259) (Table XIX (56,257-259)). The exchange rates, measured in an inert diluent, were found to be independent of free ligand concentration, consistent with a d-activation mode. 

Is this the rds There is striking correlation of the exchange rate constants for MS. and the values of k in (4.81). In addition the volumes of activation are positive for solvent exchange and interaction of M(dmf).+ (M = Mn, Co, Ni, Zn and Cd) with N-Metpp in dmf (compare Table 4.4). In spite of these two facts however, it is considered that one of two further steps, probably the first, controls the overall rate. A sitting-atop (SAT) complex is formed in which metal is attached by two bonds to the porphyrin and two N - H bonds remain intact. 

Table 8.13 Rate Parameters for Solvent Exchange on Ni(S)j+, B17, Table 2.8.

Table II Kinetic Data for Solvent Exchange and Formation of Complexes of Bivalent Transition Metal Ions In Methanol at 25°C ...

---