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

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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 (η3–C3H5)Fe(CO)3Cl, 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.

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