  Narrow-band conductors may turn insulating and magnetic as a consequence of
strong electron-electron correlation. In molecular conductors, the concomitance
of a strong Jahn-Teller coupling may give rise to the alternative possibility
of a non-magnetic insulator, with or without a static cooperative Jahn-Teller
distortion. In the latter case the insulator has Mott-like properties, with an
interesting interplay between electron-electron repulsion and the Jahn-Teller
effect, which is dynamical. We study this kind of non-magnetic insulator in a
very simple $E\otimes e$ Jahn-Teller model and we discuss its general
properties in a more general context, also in connection with the insulating
state of K_{4}C_{60} and Rb_{4}C_{60}.
