Abstract
Dissociative substitution mechanisms abound in organometallic chemistry. For certain systems, such processes can be isolated in the gas phase, where, as sequences of elementary unimolecular and bimolecular reactions, their kinetics can convey information on fundamental energetics and dynamics of metal-centered chemical transformations. Methods of competitive kinetics, using time-resolved infrared absorption spectrometry, provide relative and absolute rate constants for comparatively fast reactions. Work yielding unimolecular decay and relative bimolecular production rate constants for selected bis- and tris-ethylene complexes of iron and chromium carbonyls is summarized together with a report of new work on the CO-for-C2H4 substitution kinetics of (C2H4)Cr(CO)5.