In inner-sphere ET, the two redox centers are covalently linked during the ET. This bridge can be permanent, in which case the electron transfer event is termed intramolecular electron transfer.  More commonly, however, the covalent linkage is transitory, forming just prior to the ET and then disconnecting following the ET event.  In such cases, the electron transfer is termed intermolecular electron transfer.  A famous example of an inner sphere ET process that proceeds via a transitory bridged intermediate is the reduction of [CoCl(NH)] by [Cr(HO)].  In this case, the chloride ligand is the bridging ligand that covalently connects the redox partners.