Cobalt N-heterocyclic carbene alkyl and acyl compounds: synthesis, molecular structure and reactivity

The N-heterocyclic-carbene containing cobalt carbonyl compound [Co(IMes)(CO)3(Me)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene), 1, has been synthesised by tertiary phosphine displacement from [Co(PPh3)(CO)3(Me)]. Subsequent carbonylation afforded the acyl derivative [Co(IMes)(CO)3(COMe)], 2. Similarly, the compound [Co(IMes)(CO)3(COEt)], 3, has been synthesised. The compounds 2 and 3 have been shown to react with dihydrogen to form the cobalt hydride compound [Co(IMes)(CO)3(H)], 4. The molecular structures of compounds 1 and 2 have been determined.