Modeling the hydrodesulfurization reaction at nickel. Unusual reactivity of dibenzothiophenes relative to thiophene and benzothiophene

The nickel hydride dimer [(dippe)NiH](2) (1) was found to react with a variety of organosulfur substrates under mild conditions leading to C-S bond insertion adducts. The transition-metal insertions into the C-S bonds of thiophene, benzothiophene, and dibenzothiophene are all reversible, and lead to new organometallic complexes when dissolved in hydrocarbon solvent. (dippe)Ni(eta(2)-C,S-dibenzothiophene) (6) converts to four new organometallic species in a unique desulfurization reaction that is believed to proceed via the intermediacy of the late-metal terminal sulfide complex (dippe)Ni=S (23). Independent synthetic routes to the desulfurization products have also provided an entry into the preparation of a variety of nickel-sulfur complexes such as (dippe)Ni(SH)(2), (dippe)(2)Ni-2(mu-H)(mu-S), [(dippe)(2)Ni-2(mu-H)(mu-S)][PF6], and [(dippe)Ni(mu-S)](2), all of which have been structurally characterized. The reactivity bf 1 with 4-methyldibenzothiophene, 4,6-dimethyldibenzothiophene, 1,9-dimethyldibenzothiophene, thioxanthene, and thianthrene is also presented.