The first examples of mono and bisfluorophosphazene derived [eta(5)-cyclopentadienyl] [eta(4)-1,3-cyclohexadiene] cobalt complexes have been prepared along with the sandwich compound [eta(5)-carbomethoxycyclopentadienyl] [eta(4)-1,3bis(pentafluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadie ne] cobalt and acetylene trimerized products from the reactions of [eta(5)-MeOC(O)C5H4]Co[COD], PhC CP3N3F5 and phenylacetylene in the presence or absence of an additional cycloalkene or indene. Formation of these mono and bis fluorophosphazene derived cobalt cyclohexadiene complexes provide experimental evidence for a metallacyclopentadiene pathway for cyclohexadiene formation in CpCo catalyzed reactions. Selectivity is also observed in the formation of. bisfluorophosphazene derived cyclohexadienes which stems from the fact that two P3N3F5 units cannot be accommodated on vicinal carbon atoms of a carbacycle or metallacycle. Interestingly, reactions of beta-phenylethynyl)pentafluorobenzene with [eta(5)-MeOC(O)C5H4]Co[COD] in the presence and absence of external cycloalkene under identical reaction conditions yielded only the cis and trans isomers of the metallocene [eta(5)-MeOC(O)C5H4]Co[eta(4)-C4Ph2(C6F5)(2)] along with alkyne trimerized product indicating that the selectivity in cyclohexadiene formation is governed more by steric than electronic factors. All the new compounds were characterized by H-1, C-13, P-31, and F-19 NMR as well as mass spectrometry and elemental analysis. Mono and bispentafluorocyclotriphosphazene derived [eta(5)-cyclopentadienyl] [eta(4)-1,3-cyclohexadiene] cobalt complexes and [eta(5)-carbomethoxycyclopentadienyl] [eta(4)-bis(1,3-pentafluorophenyl)-2,4-diphenylcyclobutadiene] cobalt have also been structurally characterized by single crystal X-ray analysis.