THE CHEMISTRY OF (ETA-5-C5H5)FE(CO)2H REVISITED

The compound (η5-C5H5)Fe(CO)2H can, in spite of its reputation, be stabilized at ambient temperatures. The degradation commonly observed for this hydride appears to be a result of a chain process that is initiated by adventitious oxidant(s) but that can be inhibited by additives which render (η5-C5H5)Fe(CO)2H almost indefinitely stable; the mode(s) of action of the inhibitors apparently involves interception of the initiator and/or the chain-carrying intermediates. The hydride resonance of (η5-C5H5)Fe(CO)2H is unusually broad, the line width being both temperature- and concentration-dependent because of a rapid, reversible interaction of the hydride ligand of (η5-C5H5)Fe(CO)2H with a small amount of a paramagnetic iron species. The hydride (η5-C5H5)Fe(CO)2H also undergoes carbon monoxide substitution and hydride self-exchange reactions, the former via a chain process involving radical intermediates and the latter possibly via the dimeric intermediate [(η3-C5H5)Fe(CO)2(μ-H)]2. The tertiary phosphine substituted product (η5-C5H5)Fe(CO)(PMe2Ph)H undergoes a thermal process in which the phosphine dissociates reversibly. © 1990, American Chemical Society. All rights reserved.