Photochemistry of tricarbonyl (η5-cyclopentadienyl)(trifluoroacetyl)-molybdenum in a variety of frozen gas matrices at ca. 12 K: infrared spectroscopic evidence for carbon monoxide ejection and difluorocarbene formation by α-F elimination

Abstract

Infrared spectroscopic evidence including ¹³CO labelling is presented which shows that photolysis of [Mo(η⁵-C₅H₅)(CO)₃(COCF₃)] in frozen gas matrices (argon, methane, carbon monoxide, or nitrogen) at ca. 12 K affords stepwise ejection of CO to yield [Mo(η⁵-C₅H₅)(CO)₃(CF₃)]via the 16-electron species [Mo(η⁵-C₅H₅)(CO)₂(COCF₃)]. Subsequent photolysis of [Mo(η⁵-C₅H₅)-(CO)₃(CF₃)] produces further CO ejection reversibly to give the 16-electron species [Mo(η⁵- C₅H₅)-(CO)₂(CF₃)], which in nitrogen matrices undergoes a reversible reaction to produce cis-[Mo(η⁵- C₅H₅)-(CO)₂(CF₃)(N₂)], while in other matrices a novel fluorocarbene species, trans-[Mo(η⁵- C₅H₅)-(CO)₂(CF₂)F], corresponding to α-F elimination is observed for the first time. The mechanisms of the various photolysis steps are discussed in relation to the growing chemistry of metal–halogenocarbene complexes.