Reactions of di- and polynuclear complexes. 7. Reaction of [cyclic] [(CO)3Co(.mu.-RC2R')Co(CO)3] (R = R' = CF3, CO2Me; R = CF3, C6H5 and R' = H) with [{FeCp(CO)2}2]. Di- and tetranuclear mixed-metal complexes. Alkyne coordination and scission by a tetrametallic framework. Crystal structures of [Co3FeCp(.mu.4-.eta.2-C:CHCF3)(.eta.6-C7H8)(.mu.-CO)2(CO)4] and [Co3FeCp2(.mu.4-.eta.2-C.tplbond.CCF3)(.mu.-CO)(CO)5]