(η5-cyclopentadienyl)[η2-bis(tert-butylsulfonyl)acetylene]-(carbonyl)cobalt -: An electrophilic reagent to yield CpCo-stabilized cyclobutadiene derivatives

Various substituted (R=H, CH3, SiMe3, CO2Me, COCH3, EtMe,) (R-eta(5)-cyclopentadienyl)[eta(2)-bis(tert-butylsulfonyl)acetylene](carbonyl)cobalt complexes (8-13) proved to be very reactive towards alkynes under rather mild conditions. Dithiaacetylenes reacted at room temperature, dialkyl- and diarylalkynes had to be heated to 80-90 degreesC to yield the corresponding R-CpCo-stabilized cyclobutadiene complexes 18-37 and 39-42. X-ray investigations on 24-26, 30, 36 and 39-41 showed almost equal C-C bond lengths in the cyclobutadiene rings. (C) 2002 Published by Elsevier Science B.V.