Ab initio MO LCAO SCF simulation of molecular and electronic structure of η5-π-C60H5XCp (X=Fe, Si) complexes

Abstract

The problem of existence of η5-π-complexes of unsubstituted fullereneI h -C60 and its cyclopentadienyl type derivative C60H5 . is discussed.Ab initio MO LCAO SCF calculations of hypothetical sandwich systems η5-π-C60H5XCp (X=Fe (1a), Si (1b)), the cationic complex C60FeCp+ of unsubstituted C60, and the C60H5 . radical were performed in the STO-3G and 3-21G basis sets. In the1a, 1b, and C60H5 . systems, hydrogen atoms are attached to carbon atoms of fullerenei h -C60 at α-positions relative to the same pentagonal face (pent *). In η5-complexes, XCp species are also coordinated to this face. According to calculations in the 3-21G basis set, the Fe-pent * bond energy in complex1a is much higher than those of similar bonds in1b and in the η5-π-C60FECp+ cation (117 kcal mol−1 vs. 37 and 64 kcal mol−1, respectively) and is 7 kcal mol−1 higher than the Fe−Cp bond energy in the classical sandwich system FeCp2. The Fe…C pent* and Fe…CCp distances in complex1a are slightly shorter than the Fe…C distance in the ferrocene molecule. The spin populations in the C60H5 . radical are almost completely localized on the atoms of thepent * face, which must favor the formation of η5-π-complexes of this radical.