Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/70894
標題: DFT Studies on the Reaction of CpCo(PPh3)(2) with Diphenylphosphinoalkynes: Formation of Cobaltacycles and Cyclobutadiene-Substituted CpCoCb Diphosphines
作者: Weng, C.M.
Hong, F.E.
關鍵字: x-ray structures
cobalt-catalyzed cyclotrimerization
parallel reaction
pathways
molecular-orbital methods
aryl bond formation
metal-complexes
4-iminocobaltacyclobutene complexes
cobaltacyclopentadiene complexes
cycloaddition reactions
density
functionals
期刊/報告no:: Organometallics, Volume 30, Issue 14, Page(s) 3740-3748.
摘要: Several adiabatic potential energy surfaces (PES) were employed for probing the processes of the formation of the cobaltacycles (eta(5)-C5H5)(PMe3-kappa P)Co(1,4-C-4(PPh2)(2)R-2-1 kappa C,4 kappa C') (3P) and their conversion to CpCoCb (4; (eta(5)-C5H5)Co(eta(4)-1,2-C-4(PPh2)(2)R-2)). The former species were prepared from the reactions of (eta(5)-C5H5)Co(PMe3)(2) (0_Me) with various diphenylphosphino-substituted alkynes, RC equivalent to CPPh2 (R = H, F, CF3, CH3, Ph, Pr). The conversion of 3P to the corresponding species 4 is more feasible for an alkyne with a bulky substituent (R = Pr, Ph) than with R = H. In contrast, two conformers, 3P and 4, are energetically quite different in the case of R = H. The former is energetically more stable than the latter: -60.2 vs -46.8 kcal/mol. Moreover, a high energy barrier (ca. 67.6 kcal/mol) is present which might retard the conversion rate for 3P to 4. Likewise, it is also true for the cases with strongly electron-withdrawing groups such as R = F, CF3. This mechanistic study has been done by using DFT methods, which provides an explanation for the experimental observation that showed the conversion of (eta(5)-C5H5)(PPh3-kappa P)Co(1,4-C-4(PPh2)(2)H-2-1 kappa C,4 kappa C') (3P_n_H) to (eta(5)-C5H5)Co(eta(4)-1,2-C-4(PPh2)(2)H-2) (4_n_H) was hardly achieved thermally.
URI: http://hdl.handle.net/11455/70894
ISSN: 0276-7333
文章連結: http://dx.doi.org/10.1021/om2000025
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