Infrared spectroscopy and chemistry in liquid rare-gas solvents

This meeting is about ‘unstable’ species studied at low temperature, mostly via matrix isolation or nozzle beams. This article describes a different approach, the use of liquid rare gases (LRG) as low-temperature solvents for investigating unstable species, largely via Infrared spectroscopy, particularly those species involved in organometallic reactions. As an intorduction to the technique two examples of its application to stable compounds. are described; the i.r. spectra of SF6 in liquid Ar, of relevance to work in beams and matrices, and the thermodynamics of the gauche–trans isomerisation of CH2ClCH2Cl. The main part of the paper concerns the generation of novel η2-H2 complexes of transition metals, which is achieved by photolysis of parent metal carbonyls in H2-doped LRG. In particular we are concerned with the bonding of the η2-H2 moiety to the transition metal, and the nature of this non-classical interaction can be probed by isotopic and temperature effects on the ν(H—H) i.r. band.