Matrix photochemistry of ethyltrioxorhenium(VII), C2H5ReO3: Tautomerisation via β-hydrogen migration with the sequential formation of two different ethene derivatives

IR spectroscopic measurements have been used to chart the matrix photochemistry of ethyltrioxorhenium(VII). Broad-band UV-visible light (200 ≤ λ ≤ 800 nm) results in the migration of a β-hydrogen atom of the ethyl group with the sequential formation of two tautomers, the first a weakly OH-bound ethene complex, C₂H₄·HOReO₂, and the second the η²-coordinated ethene derivative (η²-C₂H₄)Re(OH)O₂. There is no evidence of the carbene derivative CH₃CHRe(OH)O₂ which might have been expected by analogy with the behaviour of methyltrioxorhenium, CH₃ReO₃, under similar circumstances. Assignments of the IR absorption bands are made and their carriers identified on the basis of experiments with C₂D₅ReO₃ and CH₃CD₂ReO₃ and by comparison with the vibrational properties either forecast by density functional theory (DFT) calculations or determined experimentally for related molecules.