The Nature of the Ring-Opening Process in a Substituted Cyclopropylmethyliron Complex

Abstract

Irradiation of CpFe(CO)2(2,2-dimethylcyclopropylmethyl) (4) in the absence and presence of triphenylphosphine leads to the ring-opened and CpFe(CO)(PPh3)CH2CMe2CHCH2) (7). These are interconverted on further irradiation and on heating are more slowly converted to the π-allylic complex CpFe(CO)(η3CH2CHCHCHMe2) (8). Ring-opening rearrangement in the sense to produce mainly 6 or 7 (with a primary σ-bonded alkyl group) rather than products derived from a tertiary σ-bonded alkyl group is most consistent with a concerted four-center organometallic rearrangement process. A radical route, previously proposed for the unsubstituted cyclopropylmethyl complex, is unlikely. Complex 4 also undergoes normal migratory insertion to an acyl complex, without opening of the cyclopropylmethyl group.