Photochemistry of iron pentacarbonyl in poly(vinyl chloride), polytetrafluoroethylene and low-density polyethylene films at 12–298 K: Infrared spectroscopic evidence for the reversible formation of the carbon monoxide loss products iron tetracarbonyl and tricarbonyl, and their reactions with species in the films

✍ Scribed by Richard H Hooker; Antony J Rest

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 979 KB
• Volume: 4
• Category: Article
• ISSN: 0268-2605
• DOI: 10.1002/aoc.590040209

✦ Synopsis

Abstract

Infrared spectroscopic evidence (CO stretching region) is presented to show that near‐UV irradiation (280 < λ < 350 nm) of Fe(CO)~5~ in lowdensity polyethylene (LDPE), poly(vinyl chloride) (PVC) and polytetrafluoroethylene (PTFE) films at ca 12 K affords the coordimatively unsturated species Fe(CO)~4~ and Fe(CO)~3~. The species Fe(CO)~3~ recombines with CO at ca 60 K whilst Fe(CO)~4~ recombines at ca 80 K. The species also react with the polymeric medium and with residual solvent molecules [hexane, dichloroethane, tetrahydrofuran (THF)] in the films. The species Fe(CO)~4~…(PVC) and Fe(CO)~4~…(dichloroethane), in which the Fe(CO)~4~ fragments are probably coordinated by chlorine atoms in the PVC or solvent molecules, are less thermally stable than Fe(CO)~4~(THF) and are converted to Fe(CO)~5~ on warming the films to above ca 140 K. Similarly, the species Fe(CO)~4~(LDPE) and Fe(CO)~4~(hexane), arising from interaction of Fe(CO)~4~ with hydrogen atoms in the polymer or solvent molecules, are converted to Fe(CO)~5~ on warming the films from ca 100 K to ca 130 K. The major product formed in LDPE films at 298 K is probably Fe(CO)~4~(olefin) arising from olefin impurities in the poly(ethylene), whilst in the PVC films in the presence or absence of THF the major product resembles (η^3^–C~3~H~5~)Fe(CO)~3~Cl, i.e. Fe(CO)~4~ and Fe(CO)~3~ fragments bound to allyl chloride impurities in the PVC. The potential of polymer films for trapping and characterizing unstable species is discussed.