η3:η1 η2-TAUTOMERISM IN CARBONYLIRON COMPLEXES. INFLUENCE OF SUBSTITUENTS

Article abstract of DOI:10.1016/0022-328X(84)80094-7

A number of chelate η³-allylcarbamoyl iron complexes (1) with different substituents (R in the allyl ligand and R' at the nitrogen atom) were synthesized.The influence of structural features on the equilibrium between the complexes I and their η²-azadiene tautomers (II) was studied by IR spectroscopy.It was established that the equilibrium position is determined in the first place by steric factors.When R is a bulky substituent the equilibrium is shifted towards the cyclic form I, whereas the branching of the alkyl substituent R' at the nitrogen atom favours the open olefinic form II.Furthermore ?-?-(N) rearrangement of complexes II to ?-(N) derivatives (III), and the conversion of III into η⁴-azadiene complexes (IV) also depend on the steric requirements of the substituents R and R'.