5177-75-3Relevant articles and documents
Transition-Metal-Carbene Chemistry. Structure, Thermodynamics, and Reactivity of RhCH2+ in the Gas Phase
Jacobson, D. B.,Freiser, B. S.
, p. 5870 - 5876 (2007/10/02)
The first studies invoving a second-row transition-metal methylidene ion, RhCH2+, in the gas phase using Fourier transform mass spectrometfy (FTSM) are described.Product distribution for the reactions of RhCH2+ with hydrogen, methane, ethane, ethene, propene, and cyclopropane are reported.The methylene bond strength, D0(Rh+-CH2), was bracketed between 92 and 95 kcal/mol from which D0(Rh+-CH2) = 94 +/- 5 kcal/mol is assigned.Structural studies clearly indicate formation of a methylidene-rhodium complex instead of a hydrido-metyhylidene species.Collisional activation of RhCH2+ yields both RhC+ and Rh+, suggesting that α-hydride abstraction in RhCH2+ can occor.RhCH2+ reacts readily with both hydrogen and methane and represents the first example of methane activation by a cationic mononuclear transition-metal complex in the gas phase.The activation energy for methane elimination from Rh(H)(CH3)+ appears to be less than 5 kcal/mol. α-Hydride abstraction from Rh(CH3)+ resulting in methane elimination is found to be facile.Reactions of Rh+ with cyclopropane and RhCH2+ with ethene suggest that β-hydride elimination from a rhodacyclobutane intermediate occurs readily.Therefore, the rhodacyclobutane+ ring is belived to have significant puckering.Finally, metathesis products are observed for reactions of RhCD2+ with both ethene and propene.The results of this work are compared to earlier studies on first-row MCH2+ ions.
Reactions of FeCH2(+) and CoCH2(+) with Aliphatic Alkanes in the Gas Phase. Activation of C-H and C-C Bonds by Naked Transition-Metal Carbene Ions
Jacobson, D. B.,Freiser, B. S.
, p. 4373 - 4378 (2007/10/02)
Gas-phase reactions of the title carbenes with several aliphatic alkanes using Fourier transform mass spectrometry (FTMS) ,are described.CoCH2(+) reacts with alkanes larger than methane whereas FeCH2(+) reacts with alkanes larger than ethane.Both FeCH2(+) and CoCH2(+) react predominantly by initial C-H bond insertion with some C-C bond insertion also observed.As a consequence of facile carbene-alkyl coupling, C-C bond cleavage processes proceed predominantly with elimination of the original carbene incorporated into the departing alkane neutral.In addition a small amount of C-C bond formation product is also observed.Finally, a greater degree of H/D scrambling is observed for CoCD2(+) than for FeCD2(+).
