Mass spectrometric investigation of terminal olefin metathesis and polymerization onto W(CO)(6) and Mo(CO)(6)/CCl4, CBr4/hv catalyst systems in gas-phase


Kavakli C., Salih B.

Conference of the NATO-Advanced-Study-Institute on Ring Opening Metathesis Polymerisation and Related Chemistry, POLAICA-ZDROY, Poland, 3 - 15 September 2000, vol.56, pp.437-449 identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 56
  • City: POLAICA-ZDROY
  • Country: Poland
  • Page Numbers: pp.437-449

Abstract

We attempted to form a metathetic catalyst using W(CO)(6) and MO(CO)(6)/CCl4, CBr4 in the gas phase reaction by UV-irradiation and use this catalyst in a model metathesis reaction of 1-heptene. We analysed both the intermediate volatile compounds using an on-line mass spectrometer and the structure of the solid polymer by FI-MS and DSC. Scanning tunnelling microscopy (STM) was used in order to study the structures of W(CO)(6) and photogenerated W(CO)(6)/CCl4 catalyst on Highly Oriented Pyrolitic Graphite (HOPG). Color changes observed during UV-irradiation were considered to be an indication of the formation of the W(CO)(6)/CCl4 catalyst. The volatile compounds identified by mass spectrometer supported the formation of the catalyst. The mass spectra obtained with the field ionization mass spectrometer revealed that the catalyst may be in an oligomeric form with (CO)(4)WC2Cl2 repeating units. Thermal transitions observed in the DSC thermograms indicated the existence of oligomeric chains. STM images clearly showed the structure of the W(CO)(6) molecules with one atomic level displacement. The STM images of the catalyst verified that the W(CO)(6)/CCl4 based metathesis catalyst is composed of oligomeric chains with four tungsten atoms. When CBr4 was used instead Of CCl4 in the gas-phase the W(CO)(6) and MO(CO)(6) catalyst showed metathetic activity for 1-heptene. In this case, the volatile compounds were different from CCl4. We also tried to obtain the radical occurrence during the catalyst production. In these experiments, CCl4 and CBr4 gas mixtures were used with W(CO)(6) and MO(CO)(6), and we analysed the volatile products in the gas-phase by GC-MS.