  We review some theoretical aspects connected with the interplay of strong
electron correlations and vibron phenomena in negative fullerene ions and in
solid fulleride conductors, superconductors and insulators. The first part
covers molecular ions, their intra-molecular Jahn-Teller effect, Coulomb
(Hund's rule) exchange interactions, molecular vibrons and multiplet
splittings. The second part addresses electron propagation in molecular
fullerides, with special emphasis given to trivalent cases such as K3C60 and
NH3 K3C60, where metallic, superconducting and Mott insulating phases are at
play. Dynamical mean field theory approaches to a simplified Hamiltonian for
this system are discussed in the light of some of the observed phenomenology.
It is argued in particular that NH3 K3C60 is a Mott-Jahn-Teller insulator,
which under pressure turns into a strongly correlated superconductor, thus
sharing some important elements with the high-Tc cuprates.
