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 vari ety of organosulfur substrates under mild conditions leading to C-S bond in sertion adducts. The transition-metal insertions into the C-S bonds of thio phene, 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 sp ecies 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 p rovided an entry into the preparation of a variety of nickel-sulfur complex es 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 structura lly characterized. The reactivity bf 1 with 4-methyldibenzothiophene, 4,6-d imethyldibenzothiophene, 1,9-dimethyldibenzothiophene, thioxanthene, and th ianthrene is also presented.