McMurry reactions of (η5-acetylcyclopentadienyl) cobalt-(η4-tetraphenylcyclobutadiene) with benzophenone: ketone couplings and a pinacol/pinacolone rearrangement

Abstract

The reaction of (η4-C4Ph4) Co[η5-C5H4–C(O)Me], 5, with benzophenone under McMurry conditions (TiCl4/Zn/THF) gives the hetero-coupled product (η4-C4Ph4)Co[η5-C5H4–C(Me)CPh2], 7, together with the dicobalt species: trans-(η4-C4Ph4)Co[(η5-C5H4–C(Me)C(Me)-η5-C5H4−)] Co(η4-C4Ph4), 9, and the pinacolone Me[(η4-C4Ph4)Co(η5-C5H4)]2C–C(O)Me, 10. The latter is apparently formed from the pinacol by migration of an (η4-C4Ph4)Co[(η5-C5H4) group. …