Both uncharged transition metal complexes and anionic complexes lead to the required adducts with acidic boranes. On the right is a typical reaction of a Z-ligand where the electron deficit BPh adds to the anionic Fe complex. The presence of Cp and CO ligands further stabilize the Fe-BPh bond. More specific examples include [NEt][CpFe(CO)] which gives the anionic borane iron complex as an amorphous solid from reaction with BPh in diethyl ether. This could even be characterized in solution by a high-field shifted B-NMR signal at −28.8 characteristic of fourfold coordinated boron.