New iron complexes from nucleophile addition/carbonylation of η4-(1,3-diene)tricarbonyliron(0) complexes

A series of novel organoiron complexes has been isolated and studied by ¹H NMR, ¹³C NMR, and IR spectroscopy. Addition of LiC(CH₃)₂CN to (1,3-cyclohexadiene)tricarbonyliron produces an intermediate which is only stable at low temperature and which is assigned the homoallyl—Fe(CO)₃ anion structure. The intermediate rearranges on warming into a stable complex, for which full spectral data support the structure as an allyl—Fe(CO)₃ anionic species. Interception of the first formed intermediate with CO gives an acylferrate complex with an olefin unit still bound to iron, and methylation then occurs at oxygen to produce an unusual internally-bound (alkene)(methoxyalkylidene)tricarbonyliron species.