252970-59-5Relevant academic research and scientific papers
Synthesis and Structural Characterization of Novel Organometallic Dehydroannulenes with Fused CpCo-Cyclobutadiene and Ferrocene Units Including a Cyclic Fullerenyne Segment
Bunz, Uwe H. F.,Roidl, Gaby,Altmann, Markus,Enkelmann, Volker,Shimizu, Ken D.
, p. 10719 - 10726 (1999)
The synthesis of fused organometallic dehydroannulenes containing cyclobutadiene(cyclopentadienyl)-cobalt or ferrocene units separated by butadiyne linkers is presented. Starting from the corresponding 1,2-diethynylated sandwich complexes, either Eglinton, Hay, or Voegtle-type coupling furnishes the desired dehydroannulenes. The choice of the coupling variant is critical for the success of this reaction. It was found that for diethynylferrocene a variant of the classic Eglinton system utilizing a Cu2Cl2/CuCl2 mixture in pyridine works successfully, while for the case of the cyclobutadiene(cyclopentadienyl)cobalt complexes the Voegtle coupling utilizing Cu(OAc)2 in acetonitrile gave the most impressive results, leading to a 87% yield of cyclized material. To obtain perethynylated organometallic dehydroannulenes, a novel synthesis of tetraethynylated cyclobutadiene complexes was developed. Flash vacuum pyrolysis of a bisbutadiynylated CpCo-ligated cyclobutadiene furnishes the desired tetraethynylated cyclobutadiene complex via a Bergman-type rearrangement. The two TMS and two TIPS substituents of the cyclobutadiene complex are oriented pairwise ortho with respect to each other. Removal of the TMS groups accesses a monomer, which under the conditions of the Voegtle coupling cyclizes to novel trimeric and tetrameric, perethynylated, cyclobutadieno fused, organometallic dehydroannulenes.
