Terminal coordination of diatomic boron monofluoride to iron

Iron's new Best Friend Carbon monoxide (CO) is one of the most widely studied ligands in the chemistry of transition metals. One of its distinguishing features is a two-way bonding motif, in which CO donates electrons to the metal while the metal simultaneously engages in “back bonding” in the other direction. Theory has suggested that the isoelectronic boron fluoride diatomic, BF, would be even more effective at both types of bonding. However, it has been challenging to prepare the requisite compounds for comparison. Drance et al. now report synthesis of a terminal iron-BF complex, with donor and acceptor characteristics that compare favorably to analogous CO and N 2 complexes. Science , this issue p. 1203