University of Illinois Urbana-Champaign

Reactions of Manganese Carbonyl Radicals: Electron Transfer, Atom Transfer and Substitution

Mccullen, Sharon Brawner

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Description

Title
Reactions of Manganese Carbonyl Radicals: Electron Transfer, Atom Transfer and Substitution
Author(s)
Mccullen, Sharon Brawner
Issue Date
1982
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(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)(.).
Graduation Semester
1982
Type of Resource
text
Permalink
http://hdl.handle.net/2142/70185

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