Accession Number : ADA113790

Title :   Steric Effect of Phosphorus Ligands on Fe(CO)4(P-Donor) and Ru3(CO)9(P-Donor)3 Photocatalyzed 1-Pentene Isomerization.

Descriptive Note : Technical rept.,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY

Personal Author(s) : Graff,James L ; Sanner,Robert D ; Wrighton,Mark S

PDF Url : ADA113790

Report Date : Apr 1982

Pagination or Media Count : 36

Abstract : Photoexcitation at 355 nm of Fe(CO)4L and Ru3(CO)9L3 (L=CO, PPh3, P(OMe)3, and P(O-o-toly1)3) can be used to generate catalysts for the isomerization of 1-pentene to cis-and trans-2-pentene. Each complex gives a different initial ratio of trans- to cis-2-pentene ranging from approximately 6 for Ru3(CO)12 and Ru3(CO)9(P(OMe)3)3 to approximately 1 for Fe(CO)4P(O-o-toly1)3. Comparisons of the initial ratios of the isomeric products shows that steric effects, not electronic effects, of the P-donor ligands are responsible for the variation in isomer ratio. The more sterically demanding complexes give the smallest ratio of trans-to cis-2--pentene. Thus, sterically crowded complexes give enrichment of the less thermodynamically stable alkene. Similarly, beginning with cis-2-pentene, Fe(CO)3(PPh3)2 gives a much smaller ratio of trans-2-pentene to 1-pentene at low conversion than does Fe(CO)5 under 355 nm irradiation. Initial quantum yields for isomerization generally exceed unity and the ultimate distribution of alkenes is the thermodynamic ratio, evidencing the photochemical formation of a thermally active catalyst. For Fe(CO)4L the only detected primary photoprocess is dissociative loss of CO with a quantum yield of approx. 0.4, while for Ru3(CO)9L3 the primary photoprocess is proposed to be rupture of a metal-metal bond. (Author)

Descriptors :   *Photochemical reactions, *Phosphorus compounds, *Ligands, *Catalysts, *Isomerization, Organometallic compounds, Ruthenium, Electron donors, Pentanes, Thermochemistry, Iron compounds, Stereochemistry, Cobalt, Ratios

Subject Categories : Organic Chemistry
      Radiation and Nuclear Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE