A biphasic displacement of [60]fullerene from fac-(dihapto-[60]fullerene)(dihapto-1,10-phenanthroline) tricarbonyl molybdenum (0)

The Lewis bases (=L) triphenylphosphine (PPh3) and tricyclohexyl phosphine (P(Cy)3) displace [60]fullerene (C60) from the complex fac-(η2-C60)(η2-phen)Mo(CO)3 (phen = 1,10-phenanthroline). The progress of the reactions was followed observing the decrease of the absorbance values at 440 nm and by monitoring the stretching carbonyl region from 1700 to 2100 cm−1. The plots of absorbance vs. time were biexponential, indicative of a biphasic behavior, for reactions under flooding conditions where [L] ≫ [fac-(η2-C60)(η2-phen)Mo(CO)3]. The plot of absorbance vs. time consisted of two consecutive segments: the first segment of the plot was a decrease of absorbance with time followed by a second segment where the absorbance increased with time. The first segment of the biphasic plot was ascribed to the solvent-assisted displacement of C60 from fac-(η2-C60)(η2-phen)Mo(CO)3 and the second segment to decomposition of the complex fac-(η1-L)(η2-phen)Mo(CO)3 produced in the first of the two consecutive reactions. The rate constant values corresponding to the first segment of the biphasic plot are independent of the chemical nature of L, the molar concentration of L, and the molar concentration of C60 but dependent on the chemical nature of the solvent.

The ligand/[60]fullerene exchange reactions on fac-(η2-C60)(η2-phen)Mo(CO)3 are biphasic where the first segment of the biphasic plot corresponds to formation of fac-(η1-L)(η2-phen)Mo(CO)3 and the second segment corresponds to decomposition of fac-(η1-L)(η2-phen)Mo(CO)3. Results from this investigation support some degree of solvent–Mo bond formation in the transition state leading to formation of fac-(solvent)(η2-phen)Mo(CO)3. The Mo–C60 bond is estimated to be in the vicinity of 110 kJ/mol.Figure optionsDownload as PowerPoint slide