ISSN:
0894-3230
Keywords:
nucleophilic addition
;
electron transfer
;
carbonylmetallate salts
;
donor-acceptor interactions
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
---The isostructural pentacarbonylmetallate anions M(CO)-5 (M=Mn and Re) react with a series of N-methylpyridinium cations (Py+) to yield products of nucleophilic addition [NA=Py-M(CO)5] or of one-electron redox reaction [ET=Py·+M(CO)·5]. The partitioning of the reaction along the two reaction pathways is controlled by steric factors and the electronic structure of the pyridinium cation, with cations which form stable, delocalized radicals favoring the ET pathway. The central metal also plays a role in determining the stoichiometry, and the NA pathway is favored by the rhenate anion and ET by the manganate analogue. Rates of both reactions correlate with the driving force for electron transfer, and the differing reaction pathways are not distinguished on the basis of linear free energy relations, previously discussed by Bordwell and co-workers. The contact ion pair [Py+, M(CO)-5] is identified as the critical precursor for both electron transfer and nucleophilic coupling. Based on these observations, it is proposed that the rates and mechanisms of these interionic reactions are controlled by donor-acceptor bonding in the transition states, which in turn is directly related to the charge-transfer interactions extant in the ion-pair intermediate. © 1997 John Wiley & Sons, Ltd.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
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