Using density functional theory based calculations, we have systematically studied the equilibrium geometries, relative stabilities, and electronic and magnetic properties of Fe and Mn atoms interacting with a varying number of BO2 moieties. These clusters are found to exhibit hyperhalogen behavior with electron affinities as high as 6.9 eV once the number of BO2 moieties exceed the nominal valences of these transition metals toms, namely 2 for both Fe and Mn. In all cases the transition metal atoms retain a sizable spin magnetic moment, even exceeding their free atom values at certain compositions. We also note that when more than two BO2 moieties are bound to neutral Fe and Mn atoms, they tend to dimerize. In the case of negative ions, this process occurs at n >= 3, thus leading to different neutral and anionic ground state geometries. The effect of these structural changes in the interpretation of photoelectron spectroscopy experiments is discussed.