C-H bond activation of thiophenes at iridium: a lower energy process than C-S bond scission

Article abstract of DOI:10.1016/0022-328X(95)05606-P

The 16-electron fragment <(triphos)IrH>, generated in situ by thermolysis of (triphos)Ir(H)2(C2H5) in THF, reacts with thiophene (T) or benzothiophene (BT) to give, in the temperature range from 67 to 100 deg C, mixtures of C-H and C-S insertion products as a result of parallel reactions .Above 100 deg C, the (thienyl)dihydride complexes convert to the thermodynamically more stable C-S insertion products (butadienethiolate and 2-vinylthiophenolate complexes) through an intramolecular mechanism which does not involve T or BT dissociation.A comparison is made to analogous reactions with dibenzothiophene. Keywords: Iridium; Thiophene; C-H activation; Hydrodesulfurization; Phosphine; Thiolate