Molecular N-2 complexes of iron stabilised by N-heterocyclic 'pincer' dicarbene ligands

The first N-2 complex stabilised by N-heterocyclic carbene ligands, Fe(C - N - C)(N-2)(2), has been obtained by the reduction of Fe(C - N - C) Br-2 where C - N - C = 2,6- bis(aryl-imidazol-2-ylidene) pyridine, aryl = 2,6-(Pr2C6H3)-C-i, with Na(Hg); it serves as a convenient precursor for other iron NHC 'pincer' complexes of the type Fe(C - N - C)(N-2) L where L = C2H4, PMe3 and Fe(C - N - C)(CO)(2).