Galloza-Rivera, Griseida

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    Ligand displacement reactions of fac-(η2-C60)(η2-phen)M(CO)3 (M = Mo, Cr, and W)
    (2009) Galloza-Rivera, Griseida; Cortés-Figueroa, José E.; College of Arts and Sciences - Sciences; Mina, Nairmen; Rios-Steiner, Jorge; Department of Chemistry; Ramirez-Vick, Jaime E.
    A mechanistic description of the ligand exchange reactions of fac-(η2-C60)(η2-phen)M(CO)3 (M = Cr, W and Mo); phen = 1,10-phenanthroline) will be presented in this work. The Lewis bases (L) piperidine (pip), triphenyl phosphine (PPh3) and tricyclohexyl phosphine (P(Cy)3) displace [60]fullerene (C60) from fac-(η2-C60)(η2-phen)M(CO)3 to produce fac-(η2-phen)(η1-L)M(CO)3 and fac-(η1-L)3M(CO)3, depending on M. The progress of the reactions were followed by observing the change of absorbance values at various wavelengths, depending on M and entering ligand (L). The reactions were also monitored by observing the stretching carbonyl region from 1700 to 2100cm-1 to establish the nature of non-steady-state intermediate species and products. The reactions of fac-(η2-phen)(η2-C60)W(CO)3 produced fac-(η2-phen)(η1-L)W(CO)3 as the only product. For M = Mo, the formation of fac-(η2-phen)(η1-L)Mo(CO)3 was followed by thermal decomposition. For, M = Cr, the formation of fac-(η2-phen)(η1-L)Cr(CO)3 was followed displacement of phen producing fac-(η1-L)3Cr(CO)3. The reactions of fac-(η2-phen)(η2-C60)Cr(CO)3 were biphasic depending on L. For example, plots of absorbance vs. time were biexponential for reactions under conditions where [L] >> [fac-(η2-C60)(η2-phen)Cr(CO)3]. The plots of absorbance vs. time consisted of two consecutive segments. The first segment (increasing) of the plot was assigned to step-wise additions of piperidine to uncoordinated C60. The second segment (decreasing) was ascribed to solvent-assisted displacement of C60 from fac-(η2-C60)(η2-phen)Cr(CO)3. The observation of an experimentally accessible isokinetic temperature suggests that the seemingly different mechanistic path for the systems investigated is actually limiting cases of the general mechanism that will be presented.