Normal-to-abnormal rearrangement and NHC activation in three-coordinate iron(II) carbene complexes

The 'normal' three-coordinate iron-NHC complex [(IPr)Fe(N′′) 2] (N″ = N(SiMe3)2) rearranges to its abnormal NHC analogue [(aIPr)Fe(N″)2] (6) on heating, providing a rare abnormal iron-aNHC complex, and the first such three-coordinate complex. The tert-butyl-substituted complex [(ItBu)Fe(N″)2] (4) undergoes a thermal decomposition that has not previously been observed in iron-NHC chemistry, resulting in the bis(imidazole) complex [( tBuIm)2Fe(N″)2] (7). A mechanism that involves consecutive C-H and C-N activation is proposed to account for the formation of 7. © 2013 American Chemical Society.