Photochemistry of methyl- and acetyl-dicarbonyl(η-cyclopentadienyl)-iron in frozen gas matrices at 12 K. Infrared spectroscopic evidence for the formation of tricarbonyl(η-cyclopentadienyl)methyliron and acetylmonocarbonyl(η-cyclopentadienyl)iron

Abstract

Infrared spectroscopic evidence is presented to show that, on photolysis of [Fe(η⁵-C₅H₅)(CO)₂(CH₃)] at high dilution in CO matrices at 12 K, a new species [Fe(η³-C₅H₅)(CO)₃(CH₃)] is produced. No evidence has been found for the formation of [Fe(η⁵-C₅H₅)(CO)(CH₃)] in Ar, CH₄, and N₂ matrices nor [Fe(η⁵-C₅H₅)(CO)₂(COCH₃)] in Co matrices, although in ¹³CO-doped matrices rapid exchange was observed. Wavelength-selective photolysis of [Fe(η⁵-C₅H₅)(CO)₂(COCH₃)] in Ar, CH₄, and CO matrices produces [Fe(η⁵-C₅H₅)(CO)₂(CH₃)]via the co-ordinatively unsaturated intermediate [Fe(η⁵-C₅H₅)(CO)(COCH₃)]. The rapid exchange of ¹²CO ligands in [Fe(η⁵-C₅H₅)(CO)₂(CH₃)] with ¹³CO in the matrix, the expanded-co-ordination-number species [Fe(η³-C₅H₅)(CO)₃(CH₃)], and the co-ordinatively unsaturated species [Fe(η⁵-C₅H₅)(CO)(COCH₃)] are discussed in relation to the mechanisms of the insertion reactions of [Fe(η⁵-C₅H₅)(CO)₂(CH₃)] and the thermal and photochemical decarbonylation reactions of [Fe(η⁵-C₅H₅)(CO)₂(COCH₃)].