Modeling the Hydrodesulfurization Reaction at Nickel. Unusual Reactivity of Dibenzothiophene 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(η2-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 sulfido complex (dippe)NidS (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)2Ni2(μ-H)(μ-S), [(dippe)2Ni2(μ-H)(μ-S)][PF6], and [(dippe)Ni(μ-S)]2, all of which have been structurally characterized. The reactivity of 1 with 4-methyldibenzothiophene, 4,6-dimethyldiben- zothiophene, 1,9-dimethyldibenzothiophene, thioxanthene, and thianthrene is also presented.