The QTAIM approach to chemical bonding between transition metals and carbocyclic rings: a combined experimental and theoretical study of ([[eta].sup.5]-[C.sub.5][H.sub.5])Mn[(CO).sub.3], ([[eta].sup.6]-[C.sub.6][H.sub.6])Cr[(CO).sub.3], and (E)-{([[eta].sup.5]-[C.sub.5][H.sub.4])CF[double bond]CF([[eta].sup.5]-[C.sub.5][H.sub.4])}[([[eta].sup.5]]-[C.sub.5][H.sub.5]).sub.2][Fe.sub.2]

Multipole refinement of high-resolution X-ray diffraction is used for obtaining the experimental charge densities for ([[eta].sup.5]-[C.sub.5][H.sub.5])Mn[(CO).sub.3], ([[eta].sup.6]-[C.sub.6][H.sub.6])Cr[(CO).sub.3], and (E)-{([[eta].sup.5]-[C.sub.5][H.sub.4])CF[double bond]CF([[eta].sup.5]-[C.sub.5][H.sub.4])}[([[eta].sup.5]]-[C.sub.5][H.sub.5]).sub.2][Fe.sub.2] and the resultant densities are analyzed by using quantum theory of atoms in molecules (QTAIM). Other QTAIM indicators, including the virial paths, the delocalization indices and the source function, have shown that for the n-hapto ([[eta].sup.n]-[C.sub.n][H.sub.n])M unit, there is a very similar level of chemical bonding for all M-[C.sub.ring] interactions.