The complexes [CpRu(BT)]+ and [CpRu(3-MeBT)]+, where BT is benzo[b]thiophene and 3-MeBT is its 3-methyl derivative, are models for π-coordination of BT to hydrodesulfurization (HDS) catalysts via the benzene ring. The BT in these complexes undergoes base-catalyzed deuterium exchange, at the 2 and 7 positions; in KOH CD3OD solutions, the exchange follows the rate law: rate = k[Ru complex][OH-]. The mechanism is proposed to involve rate-determining proton abstraction by OH- from either [CpRu(BT)]+ or [CpRu(3-MeBT)]+ followed by transfer of D+ from the CD3OD solvent to give the deuterated BT complex. Heterogeneous reactor studies of deuterium exchange of BT with D2 over several HDS catalysts (PbMo6.2S8, Co0.25MoS, and 5% Re γ-Al2O3) and γ-Al2O3 indicate that BT is activated to exchange at the 2 and 3 positions over the catalysts. These results suggest that deuterium exchange of BT over HDS catalysts may occur through routes other than those involving BT π-bonding through its benzene ring to the catalyst surface.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry