Synthesis, reactivity, and X-ray crystal structure of an anionic, mixed-metal ketenylidene cluster: [PPN][Fe2Co(CO)9(CCO)]

Article abstract of DOI:10.1021/om00094a016

The anionic mixed-metal ketenylidene cluster [PPN][Fe₂Co(CO)₉(CCO)] (1) can be prepared in high yield by a facile metal substitution reaction between [PPN]₂[Fe₃(CO)₉(CCO)] and Co₂(CO)₈ under a CO atmosphere. This cluster is structurally similar to [Fe₃(CO)₉(CCO)]^2-, but its reactivity more closely resembles that of the cationic cluster [Co₃(CO)₉(CCO)]⁺. Compound 1 undergoes protonation at the α-carbon atom to give Fe₂Co(CO)₁₀(CH) but is inert to electrophilic attack by carbocationic reagents. Nucleophilic reagents such as LiCH₃, NaOCH₃, and KBEt₃H attack at the β-carbon atom to afford dinegatively charged species [Fe₂Co(CO)₉(CC(O)R)]^2- (R = CH₃, OCH₃, H). Compound 1 crystallizes in the space group C2/c with a = 27.231 (7) A?, b = 17.670 (6) A?, c = 23.072 (10) A?, β = 126.54 (3)°, V = 8919.9 (70) A?³, and Z = 8.