Reaction between [(eta(5)-Cp')(3)Mo3S4](+) and [Ni(1,5-cod)(2)] (Cp' = methylcyclopentadienyl; 1,5-cod = 1,5-cyclooctadiene) in THF at ambient temperature yielded a coordinatively unsaturated cubane-like cluster cation, [(eta(5)-Cp')(3)Mo3S4Ni](+). The ligand sphere at the Ni atom could be saturated by coordinating dimethyl sulfide, diethyl sulfide, di(ted-butyl) sulfide, tetrahydrothiophene, thiochroman-4-ol, 1,4-dithiane, pyridine, quinoline, or 4,4'-bipyridine. The products structurally model a mode of substrate coordination on proposed binding sites of heterogeneous MoNi sulfide hydrotreating catalysts. No stable coordination compounds could be isolated for thiophene derivatives. X-ray crystal structures are reported for the ligand-bridged dicluster compounds [{(eta(5)-Cp')(3)Mo3S4Ni}(2)(mu-C4H4S2)][pts](2) (C4H8S2 = 1,4-dithiane) and [{(eta(5)-Cp')(3)Mo3S4Ni}(2)(mu-bipy)][pts](2) (bipy = 4,4'-bipyridine).