Reactions of bimetallic complexes. 4. Ligand transfer reactions between different metallic sites. Synthesis, characterization, and reactivity of acetylenic cluster and dimeric complexes of cobalt and iron. Crystal structures of [(.eta.5-C5H5)Fe(CO){.mu.-SMeCH:C(CF3)}]2 and [cyclic] [(CO)3Co(.mu.-CF3C2CF3)Co(CO)2{(SMe)Fe(.eta.5-C5H5)(CO)2}]