Insertion Reactions of Isocyanides and Nitriles into Unsupported Iron-Aryl Bonds: the Synthesis of a Dimeric Iron(II) Homoleptic Iminoacyl Complex

The reaction of the dimer Fe2Mes4 [Mes = 2,4,6-Me3C6H2 (1) with But NC led to [Fe2(η2-C(Mes)NBut)}2(μ-C(Mes)NBut)2] (2), a thermally stable homoleptic dimeric iminoacyl derivative containing both a terminal and a bridging iminoacyl functionality. 2 has a very short Fe-Fe distance [2.366(2) Å] and a low magnetic moment [3.40 μB per iron at 250 K]. A 2-fold insertion was observed in the reaction of 1 with PhCN to give dimer 3, [{(PhCN)(Mes)Fe}2{μ-NCPhMes}2], in which the iron atoms are bridged at a distance of 2.860(2) Å from each other by two imino anions. Complex 3 has a magnetic moment of 2.82 μB at 250 K, suggesting a strong magnetic coupling between the two iron atoms.