Laser flash photolysis: Photochemistry and kinetic studies of palladium(I), platinum(I), tungsten(I) and ruthenium(0) binuclear complexes

Robert Mack Granger, Purdue University

Abstract

Photogenerated (M(CNR)$\sb3\rbrack\sp{+\cdot}$ radicals, formed by $\sigma,\sigma\sp*$ homolysis of the M-M bond of $\lbrack \rm M\sb2(CNR)\sb6\rbrack\lbrack PF\sb6\rbrack\sb2$ (M = Pd, Pt; R = CH$\sb3,$ t-$\rm C\sb4H\sb9),$ are found to be significantly stronger reductants and oxidants compared to their parent ground state dimers. The kinetics of electron transfers to and from photogenerated (M(CNR)$\sb3\rbrack\sp{+\cdot}$ radicals have been examined by laser flash photolysis. Photogenerated (M(CNR)$\sb3\rbrack\sp{+\cdot}$ radicals are found to be single electron reductants of a homologous series of redox tuned metallocinium electron acceptors, A$\sp+,$ $\rm(A\sp+=\lbrack Co(C\sb5H\sb5)\sb2\rbrack\lbrack PF\sb6\rbrack,\ \lbrack Co(C\sb5H\sb4COMe)(C\sb5H\sb5)\rbrack\lbrack PF\sb6\rbrack,\ \lbrack Fe(C\sb5Me\sb5)\sb2\rbrack\lbrack PF\sb6\rbrack,\ \lbrack Fe(C\sb5H\sb4Me)\sb2\rbrack\lbrack PF\sb6\rbrack,\ \lbrack Fe(C\sb5H\sb4Et)(C\sb5H\sb5)\sb2\rbrack\lbrack PF\sb6\rbrack,\ \lbrack Fe(C\sb5H\sb5)\sb2\rbrack\lbrack PF\sb6\rbrack,\ \lbrack Fe(C\sb5H\sb4CO\sb2H)$-$\rm(C\sb5H\sb5)\sb2\rbrack\lbrack PF\sb6\rbrack$ with electron transfer rate constants of up to $\rm 9.6\times 10\sp8\ M\sp{-1}s\sp{-1}.$ Photogenerated (M(CNMe)$\sb3\rbrack\sp{+\cdot}$ radicals are also found to be single electron oxidants of a homologous series of redox tuned ferrocene electron donors (D = FeCp$\sb2\sp*,$ FeCpCp*, Fe(CpMe)$\sb2,$ FeCp(CpCH$\sb2$OH), FeCp$\sb2,$ FeCp(CpI), and Fe(CpCl)$\sb2).$ The electron transfer rate constants, k$\sb{\rm e},$ for both the oxidation and reduction of (M(CNR)$\sb3\rbrack\sp{+\cdot}$ exhibit Marcus/Agmon-Levine dependence on E$\sp{\rm O}$(metallocinium/metallocene), modulated by preequilibrium loss of one isocyanide ligand for the reduction of (M(CNR)$\sb3\rbrack\sp{+\cdot}.$ Photogenerated W(CO)$\sb5\sp{-\cdot}$ radicals, formed by $\sigma,\sigma\sp*$ homolysis of the M-M bond of $\rm\lbrack Na\rbrack\sb2\lbrack W\sb2(CO)\sb{10}\rbrack$ are found to react with two electron donating ligands to form '19-electron' adducts capable of reducing CO$\sb2.$ The kinetics of formation of the '19-electron' adducts have been examined with PPh$\sb3,$ PPh$\sb2$Cy, PPhMe$\sb2$ and PMe$\sb3,$ by laser flash photolysis.

Degree

Ph.D.

Advisors

Kubiak, Purdue University.

Subject Area

Analytical chemistry|Chemistry

COinS