Unusual Iron( III ) Ate Complexes Stabilized By Li–π Interactions

Several iron( III ) complexes incorporating diamidoether ligands are described. The reaction between {Li 2 [RN(SiMe 2 )] 2 O} and FeX 3 (X=Cl or Br; R=2,4,6‐Me 3 Ph or 2,6‐ i Pr 2 Ph) form unusual ate complexes, {FeX 2 Li[RN(SiMe 2 )] 2 O} 2 ( 2 , X=Cl, R=2,4,6‐Me 3 Ph; 3 , X=Br, R=2,4,6‐Me 3 Ph; 4 , X=Cl, R=2,6‐ i Pr 2 Ph) which are stabilized by Li–π interactions. These dimeric iron( III )–diamido complexes exhibit magnetic behaviour characteristic of uncoupled high spin ( S = 5/2 ) iron( III ) centres. They also undergo halide metathesis resulting in reduced iron( II ) species. Thus, reaction of 2 with alkyllithium reagents leads to the formation of iron( II ) dimer {Fe[Me 3 PhN(SiMe 2 )] 2 O} 2 ( 6 ). Similarly, the previously reported iron( III )–diamido complex {FeCl[ t BuN(SiMe 2 )] 2 O} 2 ( 1 ) reacts with LiPPh 2 to yield the iron( II ) dimer {Fe[ t BuN(SiMe 2 )] 2 O} 2 but reaction with LiNPh 2 gives the iron( II ) product {Fe 2 (NPh 2 ) 2 [ t BuN(SiMe 2 )] 2 O} ( 5 ). Some redox chemistry is also observed as side reactions in the syntheses of 2 – 4 , yielding THF adducts of FeX 2 : the one‐dimensional chain [FeBr 2 (THF) 2 ] n ( 7 ) and the cluster [Fe 4 Cl 8 (THF) 6 ]. The X‐ray crystal structures of 3, 5 and 7 are described.