SYNTHESIS AND REACTIVITY OF HALIDE, HYDRIDE, AND ALKYL DERIVATIVES OF (PENTAMETHYLCYCLOPENTADIENYL)(BISPHOSPHINE)IRON(II)

Reaction of [Fe(acac)2]x (acac = η2-acetylacetonate) with LiCp* (Cp* = η5-pentamethylcyclopentadienyl) in the presence of PMe3 or DMPE (DMPE = Me2PCH2CH2PMe2) yields Cp*LFe(acac) (L = PMe3 (1), η1 -DMPE (2)). Compounds 1 and 2 can be isolated or treated in situ with ClSiMe3 (in the presence of PMe3 for 1) to afford Cp*L2FeCl (L = PMe3 (3), L2 = DMPE (4)). Reaction of 1 with Grignard reagents, RMgX (X = Cl, Br), in the presence of PMe3 yields either Cp*(PMe3)2FeR (R = CH3, CH2CH3) or Cp*(PMe3)2FeX (R = CMe3, CH2C6H5, C3H5). Compounds of the general formula Cp*L2FeX react with RMgX to yield Cp*L2FeR (R = H, CH3 CH2C6H6) or Cp*(PMe3)Fe(η3-C3H5). Routes to the cationic species [Cp*(PMe3)2FeL]+PF6- (L = PMe3, CO) are described. Reaction of 1 with CH3CH2MgX in the absence of PMe3 yields Cp*(PMe3)(C2H4)FeH. Treatment of this complex with dihydrogen yields a highly unstable FeIV complex, Cp*(PMe3)FeH3. The reactivity of these complexes is discussed and proposed to involve highly reactive, 16-electron unsaturated intermediates, [Cp*(PMe3)FeR] (R = H, alkyl, aryl, etc.). © 1990, American Chemical Society. All rights reserved.