University of Illinois Urbana-Champaign

The Photochemical Reactions of Dirhenium Decacarbonyl With Water and of Dinuclear Rhenium Carbonyl Complexes Substituted by Nitrogen Bases

Gard, David Richard

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Description

Title
The Photochemical Reactions of Dirhenium Decacarbonyl With Water and of Dinuclear Rhenium Carbonyl Complexes Substituted by Nitrogen Bases
Author(s)
Gard, David Richard
Issue Date
1981
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
Language
eng
Abstract
  • The photochemistry of Re(,2)(CO)(,10) with H(,2)O in THF and other solvents is examined. The final products under sunlamp irradiation are {Re(CO)(,3)OH}(,4) and H(,2) but several intermediates are also identified. Complexes which are established as crucial intermediates along the reaction pathway include HRe(CO)(,5) and eq-Re(,2)(CO)(,9)(OH(,2)). Other rhenium carbonyl hydrides are also detected but are formed through side reactions of HRe(CO)(,5). Eq-Re(,2)(CO)(,9)(OH(,2)) is produced selectively under 313 nm irradiation; quantum yield measurements at this wavelength indicate that formation of the aqua complex proceeds through dissociative substitution of H(,2)O for CO in photogenerated Re(CO)(,5)(.). The first order rate constant for CO loss from Re(CO)(,5)(.) is estimated to be approximately 10('1) s('-1). A sequence of intermediates leading from eq-Re(,2)(CO)(,9)(OH(,2)) to {Re(CO)(,3)OH}(,4) and HRe(CO)(,5) are proposed involving cross-coupling of radical species, thermal dissociation of bound H(,2)O molecules, oxidative addition of H-OH across two metal centers, and metal carbonyl hydride elimination. Supporting thermal and photochemical reactions of Re(,2)(CO)(,10) and eq-Re(,2)(CO)(,9)(OH(,2)) are also described.
  • The photochemical reactions of dinuclear rhenium carbonyl complexes containing nitrogen bases are examined. Eq-Re(,2)(CO)(,9)(CH(,3)CN) under sunlamp irradiation yields 1,2-dieq-Re(,2)(CO)(,8)(CH(,3)CN)(,2), {Re(CO)(,3)OH}(,4), and ionic products. Photolysis of eq-Re(,2)(CO)(,9)(RNH(,2)) (R = Me, Et) in heptane produces Re(,2)(CO)(,10) and a precipitate of 1,1-dieq-Re(,2)(CO)(,8)(RNH(,2))(,2). In THF, eq-Re(,2)(CO)(,9)(py) and dieq-Re(,2)(CO)(,8)(py)(,2) (py = NC(,5)H(,5)) yield identical products under photolysis--Re(,2)(CO)(,10), Re(CO)(,3)(py)(,3)('+)HRe(,4)(CO)(,16)('-), and the ortho-metalated complex HRe(,2)(CO)(,7)(py)(NC(,5)H(,4)). Dieq-Re(,2)(CO)(,8)(py)(,2) reacts at 80(DEGREES)C in benzene to yield HRe(,2)(CO)(,8)(NC(,5)H(,4)) and HRe(,2)(CO)(,7)(py)-(NC(,5)H(,4)). The similarities between the photochemical reactions of the nitrogen base substituted complexes and that of Re(,2)(CO)(,10) with H(,2)O are noted. Discussion centers on the lability of 17-electron substituted metal carbonyl radicals, dinuclear oxidative addition and CO migration and the likelihood of primary photochemical heterolytic metal-metal bond cleavage and electron transfer processes for heavily substituted complexes.
Graduation Semester
1981
Type of Resource
text
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