APPROACH TO A METALLACYCLING POLYMERIZATION - REACTIONS OF [(ETA(5)-C5H5)CO(PPH(3))(2)] WITH ALPHA,BETA-DIYNES AND ME(3)SIC-CC6H4C6H4C-CSIME(3)

Reactions of [CpCo(PPh(3))(2)](Cp=eta(5)-cyclopentadienyl) with conjugated diacetylenes were investigated in terms of the synthesis of pi-conjugated organometallic polymers. The reaction of an alpha,beta-diyne, PhC=C-C=CPh, gave three geometric isomers of dialkynylcobaltacyclopentadienes, 1a-c, and an insoluble polymeric product, 1d. A 2,4-dialkynyl complex, 2, and a 2,5-dialkynyl complex, 3, were obtained solely from Me(3)SiC=C-C=CSiMe(3) and MeC=C-C=CMe, respectively. 1,1'-Bis(trimethylsilylethynyl)-4,4'-biphenyl afforded two isomers of 1,3-dialkynylcyclobutadiene complexes, 4a and 4b. The stability of the one-electron oxidized forms of the cobaltacyclopentadiene and cyclobutadiene complexes was examined by cyclic voltammetry.