| Abstract: | Preparation and Characterization of Cationic η2-1-Butene and Acetonitrile Complexes The reaction of the species η5-C5H5M(CO)n-σ-C4H7 (M = Fe, Mo, W; n = 2, 3) with (C6H5)3CBF4 yielded – instead of the expected cationic butadiene complexes of the type η5-CpM(CO)n?1-η4-C4H6]BF4], which would have been formed in case of hydride cleavage – compounds of the type η5-CpM(CO)n η2-C4H8]BF4], which were formed by protonation of the σ-C4H7 ligands. The reaction proceeded quantitatively. The BF4? anion can be substituted by other anions, such as ClO4?, B(C6H5)4?, PF4?, and Cr(SCN)4(NH3)2]? in the complexes obtained. The mechanism of the reaction leading to the η2-bonded 1-butene complexes was determined by isotope experiments. In trying to recrystallize the butene complexes from acetonitrile the cationic complexes η5-C5H5 Fe(CO)2CH3CN]BF4 and η5-C5H5 M(CO)3CH3CN]BF4 were observed; the X-ray structure analysis of the former is reported. |
