Low-Coordinate Iron(II) Complexes of a Bulky Bis(carbene)borate Ligand

Abstract

The bulky bis(carbene)borate ligand H2B(tBuIm)2– allows for the synthesis of three- and four-coordinate iron(II) complexes, including heteroleptic H2B(tBuIm)2FeN(TMS)2 and homoleptic [H2B(tBuIm)2]2Fe. The magnetic properties of these coordinatively unsaturated complexes have been characterized by SQUID magnetometry, but no evidence of single-molecule magnet behavior is observed, despite large negative uniaxial zero field splitting. The three-coordinate complex H2B(tBuIm)2FeN(TMS)2 serves as a precursor for the synthesis of the four-coordinate mixed carbene complex H2B(tBuIm)2(iPr2Im)FeCl, which has a coordination environment similar to that found in tris(carbene)borate iron(II) chloride complexes. Despite this similarity, attempts to prepare the corresponding iron(IV) nitride were unsuccessful, suggesting that subtle structural factors are critical to stabilizing this species.