Exchange mechanisms, transition metal

A quantitative determination of such matrix elements (to be elaborated below) is of crucial importance because it not only allows an absolute evaluation of the desired rate constants but also helps to reveal the qualitative aspects of the mechanism. In particular, questions regarding the magnitude of electronic transmission factors and the relative importance of ligands and metal ions in facilitating electron exchange between transition metal complexes can be assessed from a knowledge of... 

In comparing alkaline earth-for-transition metal exchange with transition metal-for-transition metal exchange, two important differences are apparent, Because of the larger stability constants of transition metal complexes, as compared with alkaline earth metal complexes, the disjunctive mechanism is less favorable and the adjunctive exchange pathway predominates. Also, as shown in Table 4, the rate constants for adjunctive exchange are slower for transition metal complexes than for alkaline earth complexes. 

An excellent method to investigate the rate and mechanism of water exchange on transition metal polyaminecarboxylate complexes are temperatiue- and pressure-dependent NMR measurements. The active species in the water exchange for Fe Fe, and Mn is a seven-coordinate mono-aqua species. The exchange takes place between a coordinated and a bulk water molecule (Eq. (5)). 

The Mechanism of Dehydration of Alcohols over Alumina Catalysts Herman Pines and Joost Manassen Complex Adsorption in Hydrogen Exchange on Group VIII Transition Metal Catalysts... 

As indicated by the mechanism, carboalumination is a syn addition. The resulting vinylalanes react with electrophiles with net retention of configuration. The electrophiles that have been used successfully include iodine, epoxides, formaldehyde, and ethyl chloroformate.229 We will also see in Chapter 8 that the vinylalanes can undergo exchange reactions with transition metals, opening routes for formation of carbon-carbon bonds. 

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... 

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