Cyclobutadiene–metal complexes. XI. Tetramethylcyclobutadienecobalt(I) complexes

The ligand-transfer reaction of tetramethylcyclobutadienenickel chloride dimer with dicobalt octacarbonyl gave tetramethylcyclobutadienedicobalt hexacarbonyl [Me 4 C 4 Co(CO) 2 Co(CO) 4 ] and nickel tetracarbonyl. Triphenylphosphine replaced one carbonyl in Me 4 C 4 Co(CO) 2 ·Co(CO) 4 to give Me 4 C 4 Co(CO) 2 ·Co(CO) 3 PPh 3 . Both Me 4 C 4 Co(CO) 2 ·Co(CO) 4 and Me 4 C 4 Co(CO) 2 ·Co(CO) 3 PPh 3 underwent cleavage with iodine at low temperatures to give tetramethylcyclobutadienecobalt dicarbonyl iodide (Me 4 C 4 Co(CO) 2 I); this was also obtained in quantitative yield from [Me 4 C 4 NiI 2 ] 2 and Co 2 (CO) 8 . One carbonyl in Me 4 C 4 Co(CO) 2 I was replaced on reaction with triphenylphosphine, giving Me 4 C 4 Co(CO)(PPh 3 )I. Me 4 C 4 Co(Co) 2 I reacted with both sodium cyclopentadienide and [C 5 H 5 Fe(CO) 2 ] 2 to give (π-cyclopentadienyl)-(π-tetramethylcyclobutadiene) cobalt.