168283-48-5Relevant academic research and scientific papers
Insertion reactions of electrophilic iron carbene complexes with organosilanes: a synthetic and mechanistic study
Scharrer, Eric,Brookhart, Maurice
, p. 61 - 72 (1995)
Cationic iron carbene complexes of the type Cp(L)(CO)Fe=C(H)(R)+(L=PPh3, R=CH3,Ph), (L=PEt3, R=Ph, CH3, CH2CH3, CH2CH2CH2CH3, CH2CH2CH2CH2CH2CH3) have been prepared and shown to react with organosilanes to give the rpoducts resulting from insertion of the carbene unit into the Si-H bond.These reactions occur rapidly at low temperature, but yields are ca. 50percent and a counterion-dependent by-product is formed.A mechanism consistent with the experimental observations is proposed.Variable temperature NMR studies are reported which have allowed for the independent observation of several of the intermediates proposed in the mechanistic pathway.Keywords: Silicon; Iron carbene complexes; Insertion reactions; Reaction mechanism
Spectroscopic characterization and dynamic properties of cationic η2-silane and η2-H2 complexes of general structure Cp(CO)(L)Fe(HSiR3)+ and Cp(CO)(L)Fe(H2)+ (L = PEt3, PPh3)
Scharrer, Eric,Chang, Seok,Brookhart, Maurice
, p. 5686 - 5694 (2008/10/09)
The η2-H2 complexes Cp(CO)(PEt3)Fe(H2)+, 4, and Cp(CO)(PPh3)Fe(H2)+, 9, were generated by protonation of the neutral monohydride complexes with H(OEt2)2BAr′4 (Ar′ = 3,5-(CF3)2C6H3) at -78°C in CD2Cl2. The η2-H2 bonding mode was verified by observation of JHD = 31.6 Hz for 4 and JHD = 31.7 Hz for 9 in the η2-HD complexes. The classical trans dihydride Cp(CO)(PEt3)Fe(H)2+, 5, could be detected at low temperature but converts to the more stable η2-H2 complex at higher temperatures. The η2-silane complex Cp(CO)(PEt3)-Fe(HSiEt3)+, 1, was prepared by protonation of Cp(CO)(PEt3)FeSiEt3 with H(OEt2)2BAr′4, and the nonclassical structure was verified by observation of a Si-H coupling constant of 62.4 Hz. A more convenient and general method involving displacement of H2 from Cp-(CO)(PR3)Fe(H2)+ by free silane was used to prepare a series of η2-silane complexes including Cp(CO)(PEt3)Fe(H2SiPh2)+, 12, Cp(CO)(PEt3)Fe(H2SiMePh)+, 13, Cp(CO)(PEt3)Fe(H3SiPh)+, 16, Cp(CO)(PPh3)Fe(HSiEt3)+, 11, and Cp(CO)(PPh3)Fe(H2SiMePh)+, 15. Complex 13 exists as a pair of diastereomers which interconvert above -20°C (ΔG? = 12.6 kcal/mol). A mechanism involving pseudorotation in an Fe(IV) silyl hydride intermediate, Cp(CO)(PEt3)-Fe(H)(SiMeHPh)+, was proposed to account for this dynamic process. Similar dynamic properties were observed for 15 and 16.
