35038-14-3Relevant articles and documents
Product Kinetic Energy Release Distributions as a Probe of the Energetics and Mechanisms of Organometallic Reactions Involving the Formation of Metallacyclobutanes in the Gas Phase
Koppen, Petra A. M. van,Jacobson, Denley B.,Illies, Andreas,Bowers, Michael T.,Hanratty, Maureen,Beauchamp, J. L.
, p. 1991 - 2001 (1989)
Product kinetic energy release distributions and collision-induced dissociation studies are used to probe the energetics and mechanisms of several gas-phase organometallic reactions involving the formation of metallacyclobutanes.Reaction of atomic cobalt ions with 1-pentene yields Co(C2H4)+.Loss of C3H6 in this process exhibits a bimodal kinetic energy release distribution.The low-energy portion can be modeled using statistical phase space theory by assuming that propylene is eliminated.The high-energy portion of the distribution is similar to that observed for the decarbonylation of cyclobutanone by Co+ to yield Co(CO)+.It is inferred for both systems that cyclopropane elimination is being observed with a tight transition state and a reverse activation energy.The characteristically broad kinetic energy release distributions cannot be described by statistical theories.Similar results are observed with Fe+ as a reactant.In this case, however, the reaction with 1-pentene leads to a broadened rather than a bimodal distribution.These arguments are substantiated using product distributions measured in collision-induced dissociation studies of various adducts which might have structures analogous to those invoked for the reactions of Co+ and Fe+ with cyclobutanone.Metastable loss of CO is also observed in these reactions.Fitting the statistical phase space theory to the measured distribution yields a heat of formation for the cobaltacyclobutane ion of 274+/- 5kcal/mol.The heat of formation (0 K) of the ferracyclobutane ion is less well determined but is approximately 268 kcal/mol.These are substantially higher (by 27 and 16 kcal/mol, respectively) than those for the corresponding isomeric propylene complexes.From these measurements, we estimate strain energies of cobaltacyclobutane and ferracyclobutane to be 22 and 18 kcal/mol, respectively, to be compared with 26 kcal/mol for cyclobutane.