Reactivity of paramagnetic FeII-bis(amidinate) complexes

Synthesis and characterisation of ether adducts of bis(amidinate) Fe II complexes are described [amidinate = 2,6-iPr2C 6H3-NC(Ph)N-Ph]. The isolation of these five-coordinate complexes contrasts with the homoleptic bis(amidinate) Fe complexes obtained previously with the sterically more demanding amidinate ligands 2,6-iPr 2C6H3-NC(Ph)N-Ar (Ar = 2,6-iPr 2C6H3, 2,6-Me2C6H 3) The more accessible ether adducts show enhanced reactivity towards Lewis bases and towards the π-acid carbon monoxide. Reaction with excess amounts of CO results in carbonyl insertion into the Fe-N bonds, thereby giving rise to a diamagnetic bis(CO) adduct supported by two carbamoyl ligands. The influence of sterically demanding aryl substituents on the nitrogen atoms of amidinate ligands was investigated in paramagnetic bis(amidinate) Fe II complexes. Reactivity towards Lewis bases and CO is almost completely suppressed with the most bulky ligand. Gradual restoration of reactivity is observed with sterically less demanding ligands