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Title:Reactions of Manganese Carbonyl Radicals: Electron Transfer, Atom Transfer and Substitution
Author(s):Mccullen, Sharon Brawner
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Abstract:The photochemical reaction of Mn(,2)(CO)(,10) with pyridine and several alkyl- and halogen-substituted pyridines as neat solvents has been studied. Initial products of the reaction are Mn(,2)(CO)(,9)py and {Mn(CO)(,3)(py)(,3)('+)}{Mn(CO)(,5)('-)}. Continued photolysis leads eventually to {Mn(py)(,6)('+2)}{Mn(CO)(,5)('-)}(,2) as the final product. The rate of conversion of Mn(,2)(CO)(,10) and molar ratio of the final products is dependent upon the pyridine solvent. The results support a radical pathway involving electron transfer from Mn(CO)(,5-n)py(,n) to Mn(,2)(CO)(,10).(,)
The extended photolysis of Mn(,2)(CO)(,8)L(,2) with L in hexane with periodic removal of CO results in formation of Mn(CO)(,3)L(,2)(.). The Mn(CO)(,3)L(,2)(.) radicals exhibit EPR and electronic spectral features consistent with a square pyramidal geometry. The reaction of Mn(CO)(,3)L(,2)(.) with CCl(,4) indicate trans basal positions for L in the radical are favored.
The reaction of HSnBu(,3) with Mn(CO)(,3)L(,2)(.) results in HMn(CO)(,3)L(,2) as the major product. The rate of reaction exhibits first order dependence upon the concentrations of Mn(CO)(,3)L(,2)(.) and HSnBu(,3) and decreases with the increasing cone angle of L for a series of phosphorus donor ligands with similar electronic properties. For ligands with similar steric requirements, increasing the (pi)-acceptor ability of L results in a slower rate of reaction. These observations support hydrogen atom transfer from HSnBu(,3) to Mn(CO)(,3)L(,2)(.) as the rate determining step in the reaction pathway.
The reaction of Mn(CO)(,3)L(,2)(.) with CO results in formation of Mn(,2)(CO)(,8)L(,2). The reaction of Mn(CO)(,3){P(i-Bu)(,3)}(,2)(.) with CO exhibits first order dependence upon the concentrations of CO and Mn(CO)(,3)L(,2)(.) and inverse dependence upon the concentration of free ligand. For a smaller ligand such as P(n-Bu)(,3) on Mn(CO)(,3)L(,2)(.) reaction with CO is much faster. These observations support an associative reaction pathway for the substitution of L by CO on Mn(CO)(,3)L(,2)(.).
Issue Date:1982
Description:221 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
Other Identifier(s):(UMI)AAI8209607
Date Available in IDEALS:2014-12-15
Date Deposited:1982

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