The pentanuclear nickel cluster [((Pr3P)-Pr-i)Ni](5)H-6 facilitates the room-temperature hydrodesulfurization of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethydibenzothiophene. These reactions provide the new tetranuclear nickel hydride sulfide [((Pr3P)-Pr-i)Ni](4)(mu-H)(4)(mu(4)-S) (1). In comparison, the dinuclear dinitrogen nickel complex [((Pr3P)-Pr-i)(2)Ni](2)(mu-N-2) undergoes oxidative addition of the CS bonds of dibenzothiophene and 4-methyl dibenzothiophene to provide the metallacycles Ni-3((PPr3)-Pr-i)(3)C12H8S (2) and Ni-3((PPr3)-Pr-i)(3)C13H10S (3), respectively, but 4,6-dimethydibenzothiophene is unreactive, even with heating to 70 degrees C for a week. The reaction of [((Pr3P)-Pr-i)Ni](5)H-6 with (SPPr3)-Pr-i in toluene provided [((Pr3P)-Pr-i)Ni](5)H-6(S) (4), which was observed and characterized by NMR spectroscopy. The addition of vinyltrimethylsilane to 4 provided the best synthetic route to 1, with ((Pr3P)-Pr-i)Ni(eta(2)-CH2=CHSiMe3)(2) (5) generated as a byproduct.