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Title: Rare Examples of Fe(IV) Alkyl-Imide Migratory Insertions: Impact of Fe—C Covalency in (Me 2 IPr)Fe(═NAd)R 2 (R = neo Pe, 1-nor)
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Publication Date:
Journal Name:
Journal of the American Chemical Society
Page Range or eLocation-ID:
12145 to 12148
Sponsoring Org:
National Science Foundation
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  1. The effects of dispersion on migratory insertion reactions and related iron–carbon bond dissociation energies pertaining to (Me 2 IPr)FeR 2 (R = neo Pe, 1-nor), and the conversion of (Me 2 IPr)Fe(NAd)R 2 to (Me 2 IPr)Fe{N(Ad}R)R are investigated via calculations and structural comparisons. Dispersion appears to be an underappreciated, major contributor to common structure and reactivity relationships.
  2. Combining experimental and theoretical studies, we investigate the role of R-site (R = Y, Sm, Bi) element on the phase formation and thermal stability of R 2 (Mn 1−x Fe x ) 4 O 10−δ ( x = 0, 0.5, 1) mullite-type oxides. Our results show a distinct R-site dependent phase behavior for mullite-type oxides as Fe is substituted for Mn: 100% mullite-type phase was formed in (Y, Sm, Bi) 2 Mn 4 O 10 ; 55% and 18% of (Y, Sm) 2 Mn 2 Fe 2 O 10−δ was found when R = Y and Sm, respectively, for equal Fe and Mn molar concentrations in the reactants, whereas Bi formed 54% O10- and 42% O9-mixed mullite-type phases. Furthermore, when the reactants contain 100% Fe, no mullite-type phase was formed for R = Y and Sm, but a sub-group transition to Bi 2 Fe 4 O 9 O9-phase was found for R = Bi. Thermogravimetric analysis and density functional theory (DFT) calculation results show a decreasing thermal stability in O10-type structure with increasing Fe incorporation; for example, the decomposition temperature is 1142 K for Bi 2 Mn 2 Fe 2 O 10−δ vs. 1217 K for Bi 2 Mn 4more »O 10 . On the other hand, Bi 2 Fe 4 O 9 O9-type structure is found to be thermally stable up to 1227 K. These findings are explained by electronic structure calculations: (1) as Fe concentration increases, Jahn–Teller distortion results in mid band-gap empty states from unstable Fe 4+ occupied octahedra, which is responsible for the decrease in O10 structure stability; (2) the directional sp orbital hybridization unique to Bi effectively stabilizes the mullite-type structure as Fe replaces Mn.« less