172276-73-2Relevant academic research and scientific papers
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.
