The nature of bonding in some tellurium analogues of Chevrel and related phases is discussed in detail for the first time. The electronic effect, which is a characteristic feature of bonding in sulfides and selenides of this type, has been found not to occur in the closely related tellurides. A reason for this is suggested. Previously unrecognized features of bonding in Chevrel phase sulfides and selenides, and in Mo 4Ru 2Se 8 and Mo 1.5Re 4.5Se 8, are also reported. The bonding characteristics of compounds containing Mo 6, units are shown to be different from the characteristics of those containing Mo 6- x M′ x ( M′ = Ru, Rh, Re) clusters where the cluster metal M′ polarizes the chalcogen valence electrons. Cluster metal oxidation states have been found to influence both intra- and intercluster metal-chalcogen separations in a systematic and predictable fashion.