Binding affinity of alkynes and alkenes to low-coordinate iron

The synthesis, spectroscopy, and structural characterization of iron-alkyne and -alkene complexes of the type [L.sup.Me]Fe(ligand) [[L.sup.Me]= bulky [beta]-diketaminate, ligand= HCCPh, EtCCEt, C[H.sub.2]CHPh, EtCHCHEt, HCC[p-[C.sub.6][H.sub.4]OC[H.sub.3]], HCC[p-[C.usb.6][H.sub.4]C[F.sub.3]]]. The binding affinity toward the low-coordinate Fe follows the trend HCCPh> EtCCEt> C[H.sub.2]CHPh> EtCHCHEt~ PP[h.sub.3]> benzene >> [N.sub.2].